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Jou nal o Alloys and Compounds
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De elopmen and op imiza ion o no el sul u -con aining Ti-based bulk
me allic glasses and he co ela ion be ween p ima ily c ys allizing
phases, he mal s abili y and mechanical p ope ies
Lucas M. Ruschel
a,⁎
, Bas ian Adam
a
, Oli e G oss
b
, Nico Neube
a
, Maximilian F ey
a
,
Hans-Jü gen Wach e
c
, Ral Busch
a
a
Chai o Me allic Ma e ials, Saa land Uni e si y, 66123 Saa b ücken, Ge many
b
Amo phous Me al Solu ions GmbH, 66424 Hombu g, Ge many
c
He aeus AMLOY Technologies GmbH, 63450 Hanau, Ge many
a icle in o
A icle his o y:
Recei ed 6 Decembe 2022
Recei ed in e ised o m 20 Ap il 2023
Accep ed 16 May 2023
A ailable online 18 May 2023
Keywo ds:
Bulk me allic glass
Ti anium alloys
Bioma e ials
Mechanical p ope ies
The mal s abili y
Sul u
abs ac
The e ec o sul u on he glass o ming abili y, he mal s abili y and mechanical p ope ies o he eu ec ic
alloy Ti
33.4
Z
33.3
Cu
33.3
was in es iga ed by con en ional X- ay di ac ion, di e en ial scanning calo ime y
and 3-poin lexu al expe imen s. A no el egion o bulk glass o ma ion wi h a c i ical cas ing diame e o
up o 4 mm was ound in he qua e na y Ti-Z -Cu-S sys em, howe e , b i le ac u e beha io was p e-
dominan . Va ious alloying s a egies we e employed o imp o e mechanical p ope ies and a composi-
ional ansi ion om b i le o duc ile ac u e has been iden i ied (e.g. o Ti
36
Z
33.5
Cu
24.5
S
6
). A change o
he p ima y p ecipi a ing phases om a C14 La es o an in e me allic (Ti,Z )
2
Cu phase can be obse ed, as
well as a s abiliza ion o he supe cooled liquid. The o igin o he he mally uns able beha io in Ti-based
bulk me allic glasses is aced back o he easy o ma ion o he icosahed al phase upon hea ing, which is
s uc u ally close o he supposedly p edominan icosahed al sho - ange o de in he amo phous s a e. The
sys ema ic s udy ca ied ou in his wo k indica es a s ong co ela ion be ween p ima y c ys allizing phase
and he mal s abili y, bo h poin ing o he ozen sho - ange o de in he amo phous s a e which is p e-
de e mining he mechanical p ope ies. The ansi ion om he La es o he in e me allic (Ti,Z )
2
Cu phase
as well as he enla ged supe cooled liquid egion appea o be di ec ly ela ed o a des abiliza ion o he
icosahed al sho - ange o de and ul ima ely o he imp o ed mechanical p ope ies.
© 2023 The Au ho s. Published by Else ie B.V. This is an open access a icle unde he CC BY license (h p://
c ea i ecommons.o g/licenses/by/4.0/).
1. In oduc ion
Me allic glasses ha e been subjec o in ense esea ch since hei
disco e y in he ea ly 1960s [1]. Unlike c ys alline ma e ials, a oms
in amo phous me als a e a anged andomly on a long- ange o de
bu exhibi a dis inc sho - and medium ange o de on a omic
leng h scales. Compa ed o c ys alline me als o simila composi ion,
hey a e cha ac e ized by signi ican ly highe s eng h, exceedingly
high ha dness and ou s anding elas ic p ope ies [2]. Due o he high
cooling a es equi ed o supp ess c ys alliza ion and enable glass
o ma ion, i is pa icula ly challenging o p oduce amo phous me-
als e en in he o de o a ew millime e s. Alloy sys ems ha exceed
he c i ical cas ing hickness o 1 mm in con en ional cas ing p o-
cesses a e called bulk me allic glasses (BMGs). These include, o
ins ance, Z - [3], Ti- [4], Pd [5], P - [6,7], Au-[8], Mg-[9]. Fe- [10], and
Ni- [11,12] based sys ems. Among hese me al-based BMGs, Ti-based
BMGs possess g ea po en ial o p omising applica ions due o hei
low densi y, high s eng h and consequen ly high speci ic s eng h
[13–15]. The c i ical p oblem o known Ti-based alloys wi h ex-
cep ionally good glass- o ming abili y (GFA) combined wi h low
densi y is he p esence o he oxic elemen Be, p e en ing hei use
in medical applica ions [15,16]. O he good glass o me s wi hou Be
include he elemen Pd, an undesi able elemen o a ligh weigh
ma e ial due o i s high densi y and cos [16,17]. Recen ly, a p o-
mising al e na i e has been disco e ed by ou g oup wi h he new
amily o S-con aining alloys, showing high glass- o ming abili y
wi hou he use o he men ioned undesi ed elemen s. Based on
a ious eu ec ic alloys, di e en bulk glass o ming composi ions
ha e been de i ed in he S bea ing Ti-based sys em. S a ing om
he e na y eu ec ic Ti
65.5
Ni
22.5
Cu
12
[18], BMGs wi h good GFA and
high Ti con en we e de eloped using small amoun s o 4 a % S [19].
In Re . [20], o igina ing om he bina y Ti-Ni and Ti-Cu eu ec ics,
Jou nal o Alloys and Compounds 960 (2023) 170614
h ps://doi.o g/10.1016/j.jallcom.2023.170614
0925-8388/© 2023 The Au ho s. Published by Else ie B.V. This is an open access a icle unde he CC BY license (h p://c ea i ecommons.o g/licenses/by/4.0/).
]]]]
]]]]]]
⁎
Co esponding au ho .
E-mail add ess: [email p o ec ed] (L.M. Ruschel).
bulk glass o ma ion up o 3 mm wi h addi ions o Z , Cu, Ni and a S
con en o 8 a % we e achie ed. Among hem, he Ni- ee Ti-Z -Cu-S
alloys (e.g. Ti
40
Z
35
Cu
17
S
8
) a e o pa icula in e es o biomedical
applica ions, as ew o no me al ions a e eleased in o solu ion due o
hei excellen elec ochemical co osion esis ance [17,20]. Sul u
i sel is conside ed unc i ical, as i belongs o he mine als and is an
impo an componen o se e al amino acids o he human o ganism
[21]. This ensu es li le o no in e ac ion wi h human cells and
he e o e classi ies hem as biocompa ible. In pa icula , c ys alline
Ti alloys a e widely used in o hopedic p os he ics and den al im-
plan s due o hei high co osion esis ance and good biocompa -
ibili y [22–25]. Howe e , hei main d awback is he high elas ic
modulus compa ed o ha o a human bone causing e ec s like
s ess shielding and loosening o he implan s [22], whe eas he
unique s uc u e o amo phous Ti-based BMGs wi h a ela i ely low
elas ic modulus in combina ion wi h high enginee ing yield s eng h
enables hem o eme ge as a p omising al e na i e o con en ional
c ys alline implan s [23].
As o igin o he p esen wo k, he e na y eu ec ic
Ti
33.4
Z
33.3
Cu
33.3
(E5) on he coppe - ich side was chosen as new
s a ing poin o alloy de elopmen . A oya e e al. epo ed his
eu ec ic E5 as he poin wi h he lowes liquidus empe a u e in he
Ti-Z -Cu sys em, an ideal s a ing poin , as he liquid s a e is s abi-
lized o e y low empe a u es, p omo ing glass o ma ion [26,27].
Molokano and Chebo niko s udied a wide ange o alloys in he
qua e na y Ti-Z -Ni-Cu sys em, including he Ti
66.7−x
Z
x
Cu
33.3
e na y alloy se ies wi h a maximum c i ical cas ing hickness o
amo phous ibbons o 250 µm o Ti
26.7
Z
40
Cu
33.3
[28]. The c i ical
hickness o he eu ec ic composi ion E5 is epo ed as ∼200 µm
[28]. Many sys ems ha e shown ha mino addi ions o ano he
elemen esul in me allic glasses wi h imp o ed p ope ies and
enhanced GFA, i he p ope mino alloying elemen is chosen o he
espec i e base alloy [29–31]. In Ti-based sys ems, S has al eady
been p o en o be e y bene icial o amo phiza ion by inc easing
he opological a iabili y and complexi y o he sys em, hence ol-
lowing he empi ical ules o glass o ma ion [19,20,27,32]. Re-
cen ly, Wilden e al. ha e shown ha S educes he mel dynamics in
Ti-based glass- o ming sys ems, p esumably caused by he o ma-
ion o co alen in e ac ions [33]. Apa om me alloid elemen s
(e.g. S, Si o B), me als such as Sc, Ni o Al a e equen ly used as
mino addi ions [25,34–37]. The la e is o pa icula in e es as i is
a ligh elemen ha u he educes he densi y o he sys em,
p omo ing ligh weigh applica ions. Wi h espec o alloys no di-
ec ly associa ed o medical applica ions, Ni, which is opologically
equi alen o Cu, can con ibu e o enhanced glass o ma ion
[20,36,38].
In ou p e ious s udy, i was ound ha Ni- ee Ti-based bulk
me allic glasses can be o med in he Ti-Z -Cu-S alloy sys em, bu he
GFA was limi ed up o only 3 mm [20]. This wo k ocuses p ima ily
on di e en alloying s a egies in he Ti-Z -Cu-S sys em and i s e -
ec s on GFA, he mal s abili y and mechanical p ope ies. The p i-
ma y goal was o enable a la ge applica ion ield by enhancing he
GFA, howe e , i was ound ha he mechanical p ope ies (duc ile
o b i le ac u e beha io ) a e ema kably sensi i e o small com-
posi ional changes. The mechanism causing his dis inc i e change
in he mechanical pe o mance is ound o be ela ed o he liquid
and glassy s uc u e, which a e known o be domina ed by an ico-
sahed al sho - ange o de (ISRO) in Ti-based alloys [39–41]. To
deepen he unde s anding o he emb i lemen mechanism in he
s udied alloys and e en ually in Ti-based BMGs in gene al, he e-
sul s a e u he suppo ed by sys ema ic s udies o Ni and Al ad-
di ions, causing simila changes in ac u e beha io . Ul ima ely, his
allows he de elopmen o Ti-based me allic glasses wi h imp o ed
GFA as well as desi ed mechanical p ope ies o enable hei use in
po en ial biomedical applica ions.
2. Expe imen al p ocedu e
2.1. Sample p oduc ion
The alloys we e p epa ed om high pu i y aw elemen s: Ti
(99.995 w %), Z (99.99 w %), Cu (99.999 w %), Ni (99.99 w %), S
(99.9995 w %) and Al (99.99 w %). To add S in o he composi ion, a
cus om-made Cu-S p e-alloy was used, syn hesized om high pu i y
Cu and S in a qua z ube unde high pu i y a gon a mosphe e wi h
he composi ion Cu
67
S
33
(a %). Subsequen ly, he mass o he p e-
alloy was checked o iden i y any mass loss compa ed o he
weigh ed-in elemen s. The conse a ion o mass allows an accu a e
de e mina ion o he inal Cu-S composi ion assuming ha only S
(low boiling poin ) and no Cu is los in he p ocess. A de ailed de-
sc ip ion o he p oduc ion p ocess is gi en in Re . [42]. Subse-
quen ly, he aw elemen s we e alloyed oge he wi h he p e-alloy
in an elec ic a c u nace unde a Ti-ge e ed a gon a mosphe e. To
ensu e homogeneous dis ibu ion o he elemen s, he ingo s we e
lipped and emel ed a leas 5 imes. A e wa ds, he samples we e
cas unde a Ti-ge e ed high pu i y a gon a mosphe e in o wa e
cooled coppe molds using a cus om-buil suc ion cas ing machine.
Fo he poo e glass o me s, pla e-shaped specimens wi h hick-
nesses o less han 1 mm we e cas . O he wise, od-shaped samples
wi h di e en diame e s (≥ 2 mm) we e ab ica ed o de e mine he
c i ical cas ing diame e .
2.2. X- ay di ac ion and calo ime ic analysis
The samples used o X- ay di ac ion (XRD) and di e en ial
scanning calo ime y (DSC) we e cu om he cylind ical ods a a
heigh o 10 mm om he bo om igh nex o each o he . To e i y
he amo phous s uc u e as well as iden i y he c ys alline phases,
XRD measu emen s we e conduc ed using a PANaly ical X′Pe P o
di ac ome e and a D8-A25-Ad ance di ac ome e wi h mono-
ch oma ic Cu-Kα adia ion. The c oss sec ion o all specimens, in-
cluding he beams o he mechanical es s, we e cha ac e ized o
ob ain in o ma ion om he inne egion o he sample, mos c i ical
o c ys al o ma ion as i is expe iencing he lowes cooling a e.
The mal analyses we e pe o med a hea ing a es o 1 K/s in Cu
pans unde a cons an high-pu i y a gon low using a powe -com-
pensa ed Pe kin Elme DSC 8000 o de e mine he onse o he glass
ansi ion empe a u e, T
g
, and he onse o he p ima y c ys al-
liza ion, T
x
, o he amo phous samples.
2.3. Mechanical es ing
Me allic ma e ials a e con en ionally es ed in ensile es s.
Howe e , e en me allic glasses ha a e mic oscopically (in-
insically) duc ile beha e mac oscopically b i le in his mode due
o he o ma ion o one shea band unde app oxima ely 45° o he
ensile axis. This single shea band p opaga es and leads o ca a-
s ophic ailu e. Fo his eason, he mechanical pa ame e s such as
Young’s modulus, yield s eng h, ac u e s eng h and o al s ain
we e de e mined in a 3-poin beam bending (3PBB) se up using a
Shimadzu uni e sal es ing machine, as i allows he o ma ion o
mul iple shea banding ul ima ely enabling he obse a ion o in-
insic duc ili y. All beam-shaped specimens ea u e a ec angula
c oss-sec ion and we e cas in he dimension o 3 mm × 2 mm x
25 mm using he coppe mold suc ion cas ing echnique and sub-
sequen ly sanded wi h up o 1200 g i SiC pape . The suppo span L
was 20 mm. Bo h, he applied o ce F and he de lec ion D a he
cen e o he beam we e eco ded du ing he es . The enginee ing
s ess σ a he sample su ace and he s ain ε a he midpoin o he
beam we e calcula ed by simple beam mechanics heo y using he
equa ions:
L.M. Ruschel, B. Adam, O. G oss e al. Jou nal o Alloys and Compounds 960 (2023) 170614
2
FL
wh
3
22
=
(1)
and
Dh
L
6
2
=
(2)
wi h he heigh h and he wid h w o he beam.
The de lec ion a e
D
, i.e. he eloci y o he c osshead, was
cons an a 0.3 mm/min. Fo beam specimens wi h hicknesses
abou 2 mm and a suppo leng h o 20 mm, Eq. 2 p o ides a s ain
a e o 1.5×10
−4
s
−1
a he ou e ibe i
D
is used ins ead o D.
To de e mine a meaning s ain, he amp-up beha io a he
beginning o he s ess-s ain cu e was co ec ed, as desc ibed in
Fig. SI1 o he supplemen a y in o ma ion. Op imized cas ing pa a-
me e s allow de ec s such as mic opo es o be la gely elimina ed.
Howe e , o exclude andom sca e ing o he esul s in case o such
de ec s, h ee es specimens we e es ed o each composi ion.
3. Resul s
3.1. Alloy de elopmen
The GFA and he mal s abili y o he no el Ti-based alloys we e
in es iga ed by XRD and he mal analysis upon hea ing om he
glassy s a e a a a e o 1 K/s. Bo h p ope ies a e undamen al o he
p oduc ion and p ocessing o BMGs. Fig. 1a and b summa ize he
XRD esul s o he S addi ion se ies (Ti
33.4
Z
33.3
Cu
33.3
)
100−x
S
x
(x=0, 2,
4, 6, 8, 10, he ea e E5-S
x
) o a ious hicknesses, allowing o de-
e mine he c i ical cas ing hickness o he s udied alloys. Fo di-
mensions below 1 mm, pla e-shaped samples we e es ed ins ead o
od-shaped samples. The c i ical cas ing hickness o he composi-
ions con aining 2–10 a % S e eal no sha p B agg peaks om any
c ys alline phase, bu he ypical di usi e di ac ion maxima e-
p esen a i e o monoli hic me allic glasses. Howe e , he alloy
wi hou S canno be p oduced as a glass in a con en ional coppe
mold cas ing p ocess due i s low GFA, e.g. small c i ical cas ing
hickness, d
c
, o d
c
∼200 µm [28]. The composi ions ha u ned ou
amo phous we e hen cas in o molds one millime e la ge han he
c i ical cas ing hickness (d
c
+1 mm) o de e mine he p ima y c ys-
alline phases, as shown in Fig. 1b. Two domina ing c ys alline
phases, he C14 La es phase (F ank-Kaspe s uc u e) and in e -
me allic (Ti,Z )
2
Cu ( e agonal s uc u e) can be iden i ied by XRD. In
equilib ium condi ions a bcc phase is addi ionally epo ed by A -
oya e e al. o he e na y eu ec ic [26]. To conclude, an app op ia e
addi ion o S up o 4 a % signi ican ly enhances he GFA in he Ti-Z -
Cu sys em, leading o a d
c
o up o 4 mm. Fu he addi ions abo e 4 a
% lead o a con inuous dec ease o he GFA o a d
c
o 3, 0.75 and
0.5 mm o E5-S
6
, E5-S
8
and E5-S
10
, espec i ely.
The co esponding DSC scans o ully amo phous samples wi h
inc easing S-con en a e gi en in Fig. 1c, excep o E5-S
0
, as no
amo phous specimen could be p oduced in con en ional coppe
mold cas ing due o he limi ed GFA. The c ys alliza ion p oceeds ia
mul iple exo he mic c ys alliza ion eac ions o all composi ions,
al hough no all o hem ea u e a dis inc endo he mic e en as-
socia ed wi h he glass ansi ion. Fo ins ance, no dis inc glass
ansi ion could be obse ed o E5-S
2
, as he alloy s a s o c ys-
allize immedia ely as he a omic mobili y is egained in he icini y
o he glass ansi ion. Towa ds E5-S
10
, he signal o he glass an-
si ion e en is ge ing mo e and mo e p onounced, as he onse o
c ys alliza ion is shi ed con inuously o highe empe a u es, e-
lec ing a s abiliza ion o he supe cooled liquid egion (SCLR), as
summa ized in Table 1. The onse empe a u e o he glass ansi ion
T
g
o hose showing one as well as he onse o c ys alliza ion T
x
is
ma ked wi h a ows in each cu e. Each alloy was also hea ea ed
un il he i s c ys alliza ion was comple ed and subsequen ly cooled
Fig. 1. XRD pa e ns o (Ti
33.4
Z
33.3
Cu
33.3
)
100−x
S
x
(x=0, 2, 4, 6, 8, 10) a di e en
hicknesses wi h (a) showing he c i ical cas ing hickness o as-cas samples, despi e
he one wi hou S ha could no be p oduced amo phously and (b) pa ially c ys-
allized samples closely abo e he c i ical cas ing hickness. (c) DSC Scans measu ed
wi h a hea ing a e o 1 K/s o all amo phous composi ions.
L.M. Ruschel, B. Adam, O. G oss e al. Jou nal o Alloys and Compounds 960 (2023) 170614
3
down o de e mine he i s c ys alline phase ex-si u by XRD (see
Fig. SI2). The analysis e eals ha he p ima y phase upon hea ing
changes om an icosahed al phase (I-phase) o E5-S
x
(x=2,4,6,8) o
he La es phase o E5-S
10
. The e o e, he obse abili y o he glass
ansi ion h ough he inc easing s abiliza ion o he SCLR o 72 K o
E5-S
10
is di ec ly connec ed o he des abiliza ion o he quasi-
c ys alline I-phase. Howe e , he maximum in GFA and SCLR does
no coincide wi h each o he and show con a y beha io . Among
he alloys s udied, he supe cooled liquid o he bes glass o me E5-
S
4
beha es he mally e y uns able wi h almos no SCLR, in con as
o he mos s able composi ion E5-S
10
which shows a poo GFA.
As will be shown la e , he bes alloy E5-S
4
wi h espec o GFA is
mechanically b i le, whe eas he amo phous alloy Ti
40
Z
35
Cu
17
S
8
de eloped by Kuball e al. in he same quasi- e na y Ti-Z -Cu-S
sys em beha es duc ile in 3-poin lexu al es s [20]. The objec i e o
u he alloy op imiza ion is o scan he composi ional space in be-
ween o obse e and unde s and he ansi ion om b i le o
duc ile ac u e beha io . The egion o in e es is depic ed in he
quasi- e na y (Ti,Z )-Cu-S diag am in Fig. 2 and is called “connec ion
line” in he ollowing. The specimens a e labeled “CL” acco dingly.
These include he composi ions Ti
32
Z
32
Cu
32
S
4
, Ti
34
Z
32.8
Cu
28.2
S
5
,
Ti
36
Z
33.5
Cu
24.5
S
6
, Ti
38
Z
34.3
Cu
20.7
S
7
and Ti
40
Z
35
Cu
17
S
8
, which a e
u he e e ed o as E5-S
4
(as be o e), CL-S
5
, CL-S
6
, CL-S
7
and CL-S
8
,
espec i ely. The composi ion E5-S
4
( ed squa e) esul s om he
alloy de elopmen shown in Fig. 1, while CL-S
8
(blue squa e) is he
bes glass o ming alloy desc ibed in Re . [20]. The in e ening alloys
CL-S
5
o CL-S
7
(g ey squa es) a e calcula ed acco ding o a linea
equa ion. Mo e de ails on he de e mina ion a e p o ided in he
supplemen a y in o ma ion.
The XRD esul s o he “connec ion line” o bo h bulk glass
o ming egions a e shown in Fig. 3a and b o he cas ing hick-
nesses o 4 mm and 5 mm, espec i ely. The bes composi ion in
e ms o c i ical cas ing hickness om he S se ies E5-S
4
is plo ed
again o illus a e he end in GFA and he change in he p ima y
p ecipi a ing phases. Re e ing o Fig. 3a, a wide GFA ange o 4 mm
was ound anging om E5-S
4
o CL-S
6
. CL-S
7
also exhibi s a mos ly
amo phous XRD pa e n bu shows i s signs o p ima y
c ys alliza ion a he main peak o he amo phous halo. The p ima y
p ecipi a ing phase (Ti,Z )
2
Cu is mo e p ominen in CL-S
8
, which
exhibi s a GFA o 3 mm acco ding o Re . [20], hence is no expec ed
o solidi y wi hou c ys alliza ion a 4 mm. The change o he p i-
ma y c ys alline phases in cooling om he equilib ium mel can be
iden i ied mo e p ecisely in Fig. 3b, whe e he La es phase in E5-S
4
changes o a coexis ence o he La es and in e me allic (Ti,Z )
2
Cu
phase in CL-S
5
, ollowed by quasi-bina y (Ti,Z )
2
Cu in CL-S
6
o CL-S
8
.
The alloy wi h he highes GFA, CL-S
5
, exhibi s a mos ly amo phous
pa e n in addi ion o a ew B agg peaks, condensing o a c i ical
cas ing hickness sligh ly below 5 mm. In e es ingly, he maximum
in GFA is exac ly loca ed whe e he p ima y c ys alline phases a e
changing. By mo ing composi ionally close o CL-S
8
, he GFA d ops
con inuously due o he p ima y o ma ion o he less complex in-
e me allic (Ti,Z )
2
Cu. The co esponding DSC measu emen s wi h
an inc easingly he mal s abili y owa ds CL-S
8
is shown in Fig. 3c
wi h he he mal p ope ies summa ized in Table 1. All u he alloy
de elopmen s a egies we e subsequen ly pe o med on CL-S
6
(Ti
36
Z
33.5
Cu
24.5
S
6
) a he han he bes composi ion in e ms o GFA,
CL-S
5
, as i exhibi s supe io mechanical p ope ies and no b i le
ac u e ailu e, as will be shown la e (Fig. 5).
Fig. 4a and b show he XRD da a o 4 mm and 5 mm ods o
Ti
36
Z
33.5
Cu
24.5−y
Ni
y
S
6
(y=2, 4, 6, 8, 10, 12) whe e Cu is con inuously
subs i u ed wi h Ni. Rega ding a s uc u al poin o iew, Ni and Cu
a e conside ed opologically equi alen due o hei simila a omic
size [43]. The e o e, bo h a e equen ly conside ed in e changeable
[44]. Low Ni con en s do no lead o any no iceable change in he
GFA compa ed o he Ni ee a ian , as bo h alloys (y=2 and y=4) s ill
comple ely i i y in 4 mm ods and show c ys alliza ion o a dia-
me e o 5 mm. Howe e , highe Ni con en s lead o a con inuous
decline in GFA due o he o ma ion o he I-phase, ollowed by he
C14 La es phase. A simila ansi ion om an amo phous s uc u e
o he o ma ion o quasic ys als and La es phase was also epo ed
in ano he S-bea ing BMG sys em based on he e na y Ti-Ni-Cu
eu ec ic [19]. In gene al, bo h c ys alline phases a e common and
equen ly epo ed in Ti-based BMGs [15,19,36,41,45–47]. Nex o Ni
addi ion, he in luence o Al as ligh elemen was in es iga ed by
equia omic subs i u ion, keeping he elemen al a ios o he me-
chanically bes composi ion CL-S
6
cons an as shown in Fig. 4c and d.
Table 1
Calo ime ic p ope ies o ully amo phous samples s udied in his wo k. T
g
e-
p esen s he onse o he glass ansi ion empe a u e, T
x
de e mines he onse o he
p ima y c ys alliza ion, and ΔT
x
de e mines he wid h o he SCLR (ΔT
x
=T
x
-T
g
). The
c i ical diame e d
c
co esponds o XRD amo phous samples p oduced by coppe
mold cas ing.
Composi ion (a %) T
g
(K) T
x
(K) ΔT
x
(K) d
c
(mm)
Ti
33.4
Z
33.3
Cu
33.3
(E5-S
0
) - - - ∼ 0.2 [28]
(Ti
33.4
Z
33.3
Cu
33.3
)
98
S
2
(E5-S
2
) - 673 - 0.75
(Ti
33.4
Z
33.3
Cu
33.3
)
96
S
4
(E5-S
4
) 660 712 52 4*
(Ti
33.4
Z
33.3
Cu
33.3
)
94
S
6
(E5-S
6
) 699 751 52 3
(Ti
33.4
Z
33.3
Cu
33.3
)
92
S
8
(E5-S
8
) 721 782 61 0.75
(Ti
33.4
Z
33.3
Cu
33.3
)
90
S
10
(E5-S
10
) 740 812 72 0.5
Ti
34
Z
32.8
Cu
28.2
S
5
(CL-S
5
) 663 717 54 4*
Ti
36
Z
33.5
Cu
24.5
S
6
(CL-S
6
) 668 723 55 4
Ti
38
Z
34.3
Cu
20.7
S
7
(CL-S
7
) 675 729 54 4
Ti
40
Z
35
Cu
17
S
8
(CL-S
8
) 677 730 53 3 [20]
Ti
36
Z
33.5
Cu
22.5
Ni
2
S
6
666 713 47 4
Ti
36
Z
33.5
Cu
20.5
Ni
4
S
6
663 709 46 4
Ti
36
Z
33.5
Cu
18.5
Ni
6
S
6
- 704 - ∼3**
Ti
36
Z
33.5
Cu
16.5
Ni
8
S
6
- 706 - ∼3**
Ti
36
Z
33.5
Cu
14.5
Ni
10
S
6
- 711 - ∼3**
Ti
36
Z
33.5
Cu
12.5
Ni
12
S
6
- 706 - ∼3**
(Ti
36
Z
33.5
Cu
24.5
S
6
)
99
Al
1
670 720 50 4
(Ti
36
Z
33.5
Cu
24.5
S
6
)
98
Al
2
676 726 50 4*
(Ti
36
Z
33.5
Cu
24.5
S
6
)
97
Al
3
677 727 50 4
(Ti
36
Z
33.5
Cu
24.5
S
6
)
96
Al
4
680 729 49 4
(Ti
36
Z
33.5
Cu
24.5
S
6
)
95
Al
5
695 736 41 4
* Highes GFA o he espec i e se ies
** 2 mm × 3 mm amo phous beams
Fig. 2. Quasi- e na y (Ti,Z )-Cu-S diag am wi h he bes - ound glass o me s
Ti
32
Z
32
Cu
32
S
4
o his wo k as well as Ti
40
Z
35
Cu
17
S
8
om Re . [20]. The g ey squa es
indica e he ”connec ion line” composi ions.
L.M. Ruschel, B. Adam, O. G oss e al. Jou nal o Alloys and Compounds 960 (2023) 170614
4
Aluminum was conside ed a he as mic oalloying elemen and was
added in small amoun s, up o a maximum o 5 a % Al. All Al-con-
aining composi ions solidi y glassy in 4 mm molds, indica ing no
de e io a ion in GFA. In case o 5 mm cas s, Al addi ion o jus 1 a % is
no su icien o imp o e he GFA, yielding a simila c i ical cas ing
hickness as he "base" alloy CL-S
6
(compa e z=1 o Fig. 4d o CL-S6
o Fig. 3b). Fu he Al alloying o abou 2–3 a % esul in he bigges
imp o emen wi h a XRD pa e n indica ing a mos ly glassy sample
supe imposed by a ew (Ti,Z )
2
Cu/La es B agg peaks. The declining
GFA wi h inc easing Al con en goes again hand in hand wi h a
change o he p ima y c ys allizing phase om he (Ti,Z )
2
Cu in e -
me allic o a C14 La es phase. Unlike he Ni se ies, he phase change
does no occu h ough he in e media e s ep o he icosahed al
phase o ma ion. This e ec o imp o ed GFA a mino addi ion o
elemen s wi h u he de e io a ion a la ge amoun s is o en ob-
se ed in li e a u e o he so-called mic o-alloying echnique [30].
Fig. 4e and depic he co esponding DSC scans, wi h he Ni se ies
showing a con inuous des abiliza ion o he glass ansi ion un il no
T
g
is obse able (Ni ≥ 6 a %), and he Al se ies showing only a sligh
educ ion o he SCLR. The cha ac e is ic empe a u es a e sum-
ma ized in Table 1.
3.2. Mechanical p ope ies
Moni o ing he mechanical p ope ies and hei e olu ion is
pa icula ly impo an o he de elopmen o applica ion-o ien ed
alloys, especially as S-con aining Ti-based BMGs allow he usage o
indus ial-g ade aw ma e ial wi hou signi ican de e io a ion o
GFA, as shown by Kuball e al. o Ti
40
Z
35
Cu
17
S
8
in Re . [20]. A ce -
ain amoun o duc ili y is o pa icula in e es o p e en sudden
ailu e in case he applied load unexpec edly exceeds he yield
s eng h. P io o es ing, he amo phous s uc u e o he lexu al
beams was e i ied by XRD. Fig. 5a, b, and c show he 3PBB en-
ginee ing s ess-s ain cu es o h ee alloy se ies de eloped in his
wo k, he “connec ing line”, he Ni se ies as well as he Al se ies. The
no el glass o ming alloy E5-S
4
based on he Ti-Z -Cu eu ec ic E5
wi h a GFA o 4 mm ails b i le in 3PBB expe imen s wi h a o al
s ain below 2%. Such p ema u e ailu e is likely ela ed o a low
ac u e oughness, esul ing in poo esis ance o de ec s such as
mic opo es o su ace sc a ches. These allow c ack p opaga ion mo e
easily in he ensile loaded egion o he beams, u ning 3PBB ex-
pe imen s in o an elabo a e way o s udy he in insic mechanical
p ope ies. Mo ing composi ionally owa ds Ti
40
Z
35
Cu
17
S
8
, he
ansi ion om b i le o duc ile ac u e beha io occu s exac ly a
he in e media e alloy composi ion Ti
36
Z
33.5
Cu
24.5
S
6
(CL-S
6
). This
composi ion also ea u es he la ges o al s ain o ailu e o a ound
4.2% in bending o he s udied alloys. The e o e, i was chosen as
new o igin o alloy de elopmen o he Ni and Al se ies, al hough i
was no he composi ion wi h he highes GFA. The s epwise Ni
addi ion shown in Fig. 5b led o a dec ease in duc ili y, ollowed by
comple e emb i lemen a Ni con en s abo e 2 a %. Despi e hei
amo phous s uc u e, he la e do no e en each hei yield
s eng h. Simila , bu less ca as ophic emb i lemen is also ob-
se ed h oughou he Al se ies in Fig. 5c. Howe e , he bes com-
posi ion (Ti
36
Z
33.5
Cu
24.5
S
6
)
98
Al
2
in e ms o GFA s ill eaches i s
yield s eng h and exhibi s mino duc ili y be o e a al ac u e oc-
cu s. Al con en s abo e 2 a % ul ima ely led o p ema u e, b i le
ailu e. The Young’s moduli o all di e en composi ions s udied in
his wo k ange om 83 o 89 GPa in bending. A de ailed summa y o
he mechanical p ope ies σ
yield
(0.2%), σ
ac u e
, E
bending
and ε
o al
co esponding o he yield s eng h a 0.2% s ain, he ac u e
s eng h, he Young’s modulus in bending and he maximum
achie ed s ain, espec i ely, is p o ided in Table 2.
Fig. 3. (a) and (b) shows he X- ay di ac ion pa e ns o 4 mm and 5 mm as-cas
samples o he “connec ion line” composi ions. (c) The co esponding DSC scans we e
acqui ed on ully amo phous samples a a a e o 1 K/s.
L.M. Ruschel, B. Adam, O. G oss e al. Jou nal o Alloys and Compounds 960 (2023) 170614
5

Fig. 4. XRD pa e ns o 4 mm and 5 mm ods o he e alua ion o he c i ical cas ing hickness o he Ni se ies Ti
36
Z
33.5
Cu
24.5−y
Ni
y
S
6
(y=2, 4, 6, 8, 10, 12) in (a) and (b) and o he
Al se ies (Ti
36
Z
33.5
Cu
24.5
S
6
)
100−z
Al
z
(z=1, 2, 3, 4, 5) in (c) and (d). (e) and ( ) depic s he co esponding DSC scans o bo h se ies acqui ed a a a e o 1 K/s.
L.M. Ruschel, B. Adam, O. G oss e al. Jou nal o Alloys and Compounds 960 (2023) 170614
6
4. Discussion
The XRD analyses o he in es iga ed qua e na y Ti-Z -Cu-S as
well as quin ena y Ti-Z -Cu-S-Al alloys e eal he C14 La es phase as
well as he in e me allic compound (Ti,Z )
2
Cu o be he p ima y
c ys allizing phases. Conside ing he composi ion o he espec i e
alloy, he la e esul s om con inuous solubili y o Ti and Z in he
e agonal (Ti,Z )
2
Cu phase h oughou he e na y phase diag am
om Ti
2
Cu o Z
2
Cu [26]. The mix u e o Ti and Z a oms in he
e agonal sub-la ices leads o changes in he la ice pa ame e s
(Vega d’s law), esul ing in a shi o he B agg peaks as exempla ily
shown o CL-S
6
in Fig. SI3 in he supplemen a y in o ma ion. A si-
mila change in he p ima y c ys als is obse ed upon Ni addi ion o
he qua e na y Ti-Z -Cu-S sys em, al hough an addi ional quasi-
c ys alline I-phase is o med as in e media e s ep. A s abiliza ion o
he I-phase by Ni has been obse ed se e al imes, o example in
he Ti-Ni-S [20] and Ti-Z -Ni-Cu [48] sys em. Since Cu and Ni a e
conside ed o be opologically equi alen , he subs i u ion o bo h
elemen s should no a ec he s uc u e, ye S iehle e al. ound
signi ican s uc u al di e ences in he sho - and medium- ange
o de o Z -based alloys, which we e mainly a ibu ed o di e si ied
local elec onic in e ac ions [49]. In combina ion wi h he s ong
nega i e en halpy o mixing o Ni wi h Ti and Z (
Hmix
Ti Ni
=−35 kJ/mol,
Hmix
Z Ni
=−49 kJ/mol [44]), an icosahed al s uc u e seems o be
p omo ed in he liquid s a e, which is suppo ed by high-ene gy X-
ay di ac ion expe imen s o Goldman e al., who obse ed a p o-
g essi e inc ease o an ISRO by he addi ion o Ni o bina y Ti-Z [40].
Saida e al. also ound ha elemen s ha ing a posi i e o weak
chemical a ini y o one o he cons i u ional elemen s (
Hmix
Cu Ni
=4 kJ/
mol [44]) in Z - o H -based glass- o ming sys ems a e bene icial o
he p ecipi a ion o he I-phase [50]. Mo eo e , he I-phase com-
monly o ms as p ima y phase upon hea ing om he glassy s a e,
causing he he mally uns able beha io in mos o he alloys s u-
died and in gene al in Ti-based BMGs [15,45,51,52]. Some o hem,
mainly he Ni se ies, do no e en show a p onounced glass ansi-
ion, as T
g
is supe imposed by p ima y c ys alliza ion. This he mal
ins abili y is expec ed o be ela ed o s uc u al simila i ies be ween
he p edominan ISRO in he liquid/amo phous s a e and he quasi-
c ys alline I-phase, as equen ly epo ed o Ti-based BMGs
[19,39–41,53]. Those s uc u al simila i ies esul in a educed in-
e acial ene gy and consequen ly, acco ding o classical nuclea ion
heo y, in a educed nuclea ion ba ie o he I-phase [41,54–57].
The impo ance o he in e acial ene gy o he GFA o me allic
glasses has been shown o P -P-based liquids [58]. In hese liquids, a
high in e acial ene gy is able compensa e a high d i ing o ce o
c ys alliza ion and a agile liquid beha io . In he case o he Ti-
based glasses, a low in e acial ene gy due o a p onounced ISRO
esul s in an immedia e c ys alliza ion as soon as a omic mobili y is
es o ed in he icini y o he glass ansi ion. Simila phenomena
we e also obse ed in Al-based BMGs wi h high Al-con en s, whe e
he glass ansi ion is supe imposed by he apid o ma ion o cc α-
Al nanoc ys als [59–61]. Ano he indica ion o a p edominan ISRO
is e lec ed in a change o he p ima y phase upon cooling om he
e agonal (Ti, Z )
2
Cu o an icosahed al o La es phase, as he la e
con ains a high p opo ion o icosahed al clus e s [40,62,63]. This
means ha elemen s s abilizing an ISRO in Ti-based BMGs esul in
educed he mal s abili y.
Ou s udy sugges s ha he addi ion o S is an e ec i e way o
e a d/supp ess he o ma ion o he I-phase du ing hea ing, as de-
mons a ed o he E5-S
x
se ies wi h inc easing S con en . Ul ima ely
S addi ion leads o a dis inc glass ansi ion and s able SCLR (Fig. 1c)
p io o he eme gence o c ys alliza ion. The posi i e in luence o S
on he mal s abili y seems o be an almos uni e sal ea u e, as i has
al eady been demons a ed in a ious BMG sys ems, like Cu-, Z -, Ni
and Pd-based ones [32,42], [64]. In e es ingly, he maximum GFA in
he Ti-Z -Cu-S sys em (Ti
32
Z
32
Cu
32
S
4
) coincides wi h ha epo ed in
he Ti-Z -Ni-Cu-S sys em (Ti
58
Z
7.5
Ni
18.5
Cu
12
S
4
) a a sul u con en o
4 a % [19]. Cha ac e is ic a e he elemen s Ti and Z as well as Cu and
Ni, which each o m a comple e solid solu ion in hei bina y phase
diag ams [65,66]. Fu he mo e, Ti and Z ha e simila elec on con-
igu a ions, hence hey can be conside ed chemically equi alen [67].
Ni and Cu, on he o he hand, a e o en conside ed opologically equal
Fig. 5. Enginee ing s ess-s ain cu es o di e en bulk glass o ming alloy compo-
si ions measu ed in a 3PBB se up. A o al s ain o less han 2% indica es a b i le
ac u e beha io .
L.M. Ruschel, B. Adam, O. G oss e al. Jou nal o Alloys and Compounds 960 (2023) 170614
7
in me allic glass- o ming sys ems due o hei simila a omic adius
[43]. Due o hose simila i ies o Ti and Z as well as Cu and Ni, he
sys ems Ti
32
Z
32
Cu
32
S
4
and Ti
58
Z
7.5
Ni
18.5
Cu
12
S
4
can be conside ed
quasi- e na y (Ti,Z )-(Cu,Ni)-S. F om his poin o iew, he a io o
(Ti,Z ) o (Cu,Ni) is app oxima ely equal in bo h sys ems wi h wo o
one, which seem o be c ucial o he ideal sul u con en . The alloys
s udied by Kuball e al. suppo his wo king hypo hesis, as hey e-
qui e a sul u con en o 8 a % o bulk glass o ma ion (e.g.
Ti
40
Z
35
Cu
17
S
8
) due o a highe amoun o Ti and Z in he sys em [20].
Thus, he (Ti, Z ) o (Cu, Ni) a io seems o de ine he op imal S-
con en , despi e di e en p ope ies (chemical and opological) a e
compa ed wi h each o he . Fig. 6 shows he ideal S-con en equi ed
o ob ain he highes glass o ming abili y o di e en (Ti,Z )/(Cu, Ni)
a ios. The highe he Cu/Ni con en , he less S is needed o ob ain a
maximum in he GFA, as shown o a Cu-based BMG
Cu
46.3
Ti
33.5
Z
10.8
Ni
7.9
S
1.5
(Vi 101S
1.5
) o he same sys em [68]. Fu -
he mo e, he maximum achie able S con en (app ox. 8.4 a %) o
high (Ti,Z ) con en s is ma ked in he diag am. Assuming ha he GFA
maximum ollows he linea co ela ion, a simple Cu-S p e-alloy is no
longe su icien , and an addi ional Ti-S o Z -S p e-alloy is necessa y
o achie e BMGs wi h (Ti,Z ) con en s highe han ∼75 a %. The op-
imal sul u con en as a unc ion o he (Ti,Z )/(Cu,Ni) a io could be
ela ed o he size misma ch o he cons i uen a oms, which migh
exhibi an op imal dense andom packing o he a oms a ce ain
a ios. Lu e al. al eady poin ed ou ha a de ined a omic size dis-
ibu ion ins ead o an excessi e size misma ch can lead o he highes
packing densi y in he liquid and hus o an op imum in he GFA [69].
Howe e , his does no explain why he op imum S con en does no
change signi ican ly upon exchange o Ti and Z , despi e hei sig-
ni ican a omic adius di e ence o a ound 10% [43]. In o he wo ds,
he obse ed linea end canno be a ibu ed exclusi ely o opology.
Hence, he chemical con ibu ion seems o be o equal impo ance, as
he s udies by Wilden e al. a he sugges ed o sul u i sel o ma-
nipula e he chemis y o Ti-Ni-S liquids, by educing he mel dy-
namics, p esumably caused by he o ma ion o co alen in e ac ions
[33]. The mel iscosi y was mo e han doubled in he e na y Ti-Ni-S
sys em in di ec compa ison o bina y Ti-Ni. The co ela ion be ween
he maximum GFA and he (Ti,Z )/(Cu,Ni) o S con en appea s o be
decisi e and is wo h no ing, al hough u he wo k is necessa y o
sys ema ically alida e his co ela ion. A mo e gene al explana ion
o he imp o ed GFA in he sys em s udied can be a ibu ed o he
p edominan o ma ion o he I-phase as p ima y p ecipi a ing phase
upon hea ing om he glassy s a e (Fig. SI1), sugges ing an ISRO in he
liquid as epo ed in many alloy sys ems [53,70–72]. An ISRO likely
con ibu es o educed a omic mobili y coupled wi h an inc ease in
mel iscosi y [73–75]. A simila slowdown in mel dynamics is also
expec ed he e, esul ing in an imp o ed GFA.
The composi ion Ti
40
Z
35
Cu
17
S
8
is epo ed o exhibi a highe o al
s ain o ∼4.3% compa ed o he specimen o same composi ion es ed
in his wo k wi h only 3.2% (Table 2) [20]. Howe e , he highe e-
po ed s ain is no su p ising, since he measu ed sample size in his
wo k was signi ican ly la ge and he o ma ion o shea bands
s ongly depends on specimen size [76,77]. In addi ion, smalle spe-
cimens possess a highe ic i e empe a u e due o he as e cooling
a e and he e o e a highe deg ee o ee olume, p omo ing mul iple
shea band o ma ion [78–80]. Jiang e al. epo ed a simila depen-
dence o o al s ain on specimen dimensions [64]. Fo his eason, all
beams s udied in his wo k ha e he same dimensions allowing a
obus compa abili y among hem. In se e al o he S con aining sys-
ems, inc easing S con en led o an emb i lemen o he ma ix as in
Table 2
Mechanical p ope ies o he di e en alloy composi ions in es iga ed in his wo k: Enginee ing yield s eng h a 0.2% s ain σ
yield
, ac u e s eng h σ
ac u e
, he Youngs modulus
E
bending
and he o al s ain ε
o al
calcula ed om he lexu al s ess-s ain cu es.
Composi ion (a %) σ
yield
(GPa) σ
ac u e
(GPa) E
bending
(GPa) ε
o al
(%)
Ti
32
Z
32
Cu
32
S
4
(E5-S
4
) - 1.32 ± 0.4 87 ± 2 1.48 ± 0.4
Ti
34
Z
32.8
Cu
28.2
S
5
(CL-S
5
) - 1.85 ± 0.2 89 ± 1 2.09 ± 0.2
Ti
36
Z
33.5
Cu
24.5
S
6
(CL-S
6
) 2.59 ± 0.1 2.85 ± 0.1 88 ± 1 4.23 ± 0.3
Ti
38
Z
34.3
Cu
20.7
S
7
(CL-S
7
) 2.64 ± 0.1 2.79 ± 0.1 89 ± 1 3.59 ± 0.4
Ti
40
Z
35
Cu
17
S
8
(CL-S
8
) 2.58 ± 0.1 2.63 ± 0.1 87 ± 1 3.25 ± 0.1
Ti
36
Z
33.5
Cu
22.5
Ni
2
S
6
2.69 ± 0.1 2.76 ± 0.1 88 ± 1 3.44 ± 0.1
Ti
36
Z
33.5
Cu
20.5
Ni
4
S
6
- 1.40 ± 0.2 88 ± 2 1.61 ± 0.2
Ti
36
Z
33.5
Cu
18.5
Ni
6
S
6
- 1.45 ± 0.1 88 ± 1 1.66 ± 0.1
Ti
36
Z
33.5
Cu
16.5
Ni
8
S
6
- 1.03 ± 0.5 85 ± 3 1.36 ± 0.3
Ti
36
Z
33.5
Cu
14.5
Ni
10
S
6
- 1.35 ± 0.2 87 ± 2 1.59 ± 0.2
Ti
36
Z
33.5
Cu
12.5
Ni
12
S
6
- 1.18 ± 0.4 88 ± 2 1.39 ± 0.5
(Ti
36
Z
33.5
Cu
24.5
S
6
)
99
Al
1
2.51 ± 0.2 2.59 ± 0.3 88 ± 1 3.54 ± 0.4
(Ti
36
Z
33.5
Cu
24.5
S
6
)
98
Al
2
- 2.39 ± 0.1 88 ± 1 2.77 ± 0.1
(Ti
36
Z
33.5
Cu
24.5
S
6
)
97
Al
3
- 1.53 ± 0.1 83 ± 2 1.82 ± 0.1
(Ti
36
Z
33.5
Cu
24.5
S
6
)
96
Al
4
- 1.32 ± 0.3 86 ± 2 1.55 ± 0.3
(Ti
36
Z
33.5
Cu
24.5
S
6
)
95
Al
5
- 0.65 ± 0.4 86 ± 3 0.86 ± 0.3
Fig. 6. (Ti+Z )/(Cu+Ni) a io as a unc ion o he S con en o di e en BMGs in he
(Ti,Z )-(Cu,Ni)-S sys em. The composi ions Ti
40
Z
35
Cu
17
S
8
, Ti
58
Z
7.5
Ni
18.5
Cu
12
S
4
and
Cu
46.3
Ti
33.5
Z
10.8
Ni
7.9
S
1.5
o igina e om Re . [20], [19] and [68], espec i ely. The e o
ba s esul om he sc eening inc emen s o S con en pe o med o each alloy
sys em. When he S con en was sc eened in 1 a % inc emen s, he op imum S con en
is na owed down o abou ± 0.9 a %. By sc eening in s eps o 0.5 a %, he GFA max-
imum was de e mined wi h an accu acy o abou ± 0.4 a % a ound he ideal S con en .
The solid ed line ep esen s a linea i wi h a R
2
o 0.98.
L.M. Ruschel, B. Adam, O. G oss e al. Jou nal o Alloys and Compounds 960 (2023) 170614
8
he case o Cu-Z -Al-S and Pd-Ni-S alloys [42,64]. Fo Ti-based BMGs,
his seems o be di e en , as he mechanical p ope ies s ongly de-
pend on he ac ions o he esidual cons i uen s by how hey s a-
bilize o des abilize he ISRO. Ob iously, he mechanical p ope ies
a e di ec ly ela ed o he in insic amo phous s uc u e, i.e. he sho -
ange and medium- ange o de as well as ee olume in he glass
(see Fig. SI4) [38,56]. Fig. 7 schema ically depic s how a s abiliza ion/
des abiliza ion o he ISRO could be unde s ood. The schema ic on he
le side exempli ies he s uc u e o he composi ion E5-S
4
wi h he
highes GFA de i ed om he e na y Ti-Z -Cu eu ec ic. A s abilized
ISRO is indica ed by an inc eased numbe o icosahed al mo i s, which
is also expec ed o he s udied alloys con aining Ni and Al. The
o me is a well-known elemen s abilizing an icosahed al s uc u e
in Ti-based sys ems [40]. Howe e , small addi ions o Al also end o
inc ease he s abili y o icosahed al s uc u es by o ming s able Al-
cen e ed icosahed a ins ead o Cu-cen e ed icosahed a, domina ing in
Cu-Z based alloys [81]. A mo e des abilized ISRO is coupled wi h a
educed numbe o icosahed al mo i s as ou lined on he igh side o
Fig. 7. The idea is ha a ge ed alloy de elopmen s a egies (as done
o he „connec ion line“ shown in Fig. 2) lead o educed numbe o
closed-packed icosahed al mo i s, esul ing in "less densely packed"
egions wi h highe deg ee o ee olume. This p omo es he o -
ma ion o shea ans o ma ion zones and ul ima ely shea bands
[78,82], culmina ing in a ansi ion om b i le o duc ile as obse ed
in Fig. 5a om E5-S
4
o CL-S
6
. The p esen wo k sugges s ha he
p ima y o ma ion o c ys alline phases du ing cooling p o ides in-
o ma ion abou he ISRO s uc u e in he liquid s a e and hus also in
he glassy s a e i nuclea ion has been supp essed. Once quasi-c ys-
alline o c ys alline phases a e o med ha con ain icosahed al uni s
(e.g. I-phase and La es phase obse ed in all alloy se ies, see Fig. 1,
Fig. 3 and Fig. 4), i is likely ha he ISRO is s abilized, esul ing in low
he mal s abili y wi hou a dis inc SCLR [63]. Conside ing ha he
maximum s a e o an ISRO is he I-phase and ha he La es phase also
con ains a high p opo ion o icosahed al clus e s, i is no su p ising
ha Ti-based BMGs wi h a s abilized ISRO beha e mac oscopically
b i le, analogous o he complex c ys alline phases [38,63,83–85]. In
con as , he composi ions ha p ima ily o m quasi-bina y (Ti,Z )
2
Cu
in e me allic wi h a e agonal s uc u e ins ead o a complex s uc-
u e exhibi a co espondingly less p onounced, des abilized ISRO,
which ul ima ely ansla es in o imp o ed he mal s abili y and me-
chanical p ope ies (e.g. CL-S
6
, CL-S
7
and CL-S
8
in Fig. 3 and Fig. 5a).
Thus, he o ma ion o simple phases in Ti-based BMGs appea o
indica e a s uc u e ha a o s highe duc ili y in he amo phous
s a e. Fo ins ance, Wang e al. ound Ti-based BMGs wi h high
duc ili y in comp ession by in en ionally choosing a eu ec ic sys em
con aining a duc ile B2 phase ins ead o a complex phase wi h a
F ank-Kaspe s uc u e [38]. Howe e , a simple c ys alline s uc u e is
usually accompanied by educed GFA due o he highe cooling a es
equi ed o supp ess c ys alliza ion o his simple phase. He e, he
alloys wi h he highes GFA Ti
34
Z
32.8
Cu
28.2
S
5
and
(Ti
36
Z
33.5
Cu
24.5
S
6
)
97
Al
3
always p ecipi a e he complex La es phase
(see Fig. 3b, Fig. 4d), coupled by poo mechanical p ope ies. This
b i le beha io is al e ed i he p ima y c ys alline phase changes by
u he alloy op imiza ion. Ou sys ema ic s udy demons a es ha a
judicious manipula ion o he sho - ange o de h ough alloying
s a egies allows he syn hesis o composi ions wi h supe io me-
chanical p ope ies coupled wi h imp o ed GFA by analyzing he
p ima y c ys als as well as he mal s abili y. Ideally, a single XRD/DSC
measu emen is su icien o judge whe he o no alloy de elopmen
is p oceeding owa ds p omising mechanical p ope ies as he p i-
ma y c ys alline phases as well as he he mal s abili y mi o s he
p e ailing glassy s uc u e. In o he wo ds, i he I- o La es phase a e
p ima ily o med, which is ela ed o a low he mal s abili y, he e is
no need o an ex ensi e in es iga ion o he mechanical p ope ies,
since a p edominan ly b i le ac u e beha io is o be expec ed.
Howe e , i he XRD measu emen indica e a simple c ys alline
phase, such as (Ti,Z )
2
Cu, i is wo h o in es iga e he mechanical
pe o mance, as good p ope ies wi h a ce ain duc ili y a e expec ed.
To summa ize and g aphically elucida e ou indings, schema ic
ime- empe a u e- ans o ma ion (TTT) diag ams o he di e en
alloying s a egies shown in Fig. 8a o c we e cons uc ed om he
XRD c ys alliza ion da a a di e en hicknesses as well as he
knowledge o he i s c ys allizing phase upon hea ing (Fig. SI2).
Since no TTT diag ams we e measu ed expe imen ally in his wo k,
he g aphs a e simply a p oposed schema ic isualiza ion o he
indi idual alloying s a egies and hei in luence on he c ys al-
liza ion beha io . The e ec o S on he posi ion o he c ys alliza ion
cu es o he La es phase and (Ti,Z )
2
Cu phase is illus a ed in Fig. 8a
(solid blue and o ange lines). The wo lines a e d awn igh nex o
each o he , as bo h phases a e de ec ed in he XRD pa e ns. An in-
c easing S con en pushes bo h c ys alliza ion “noses” o longe
imes due o he highe GFA and lowe c i ical cooling a e equi ed
o glass o ma ion, which is e lec ed in he maximum d
c
o 4 mm a
an op imum S con en o 4 a %. E en highe S con en s in u n lead o
a educ ion in GFA o 500 µm o S
10
and hus o sho e "nose"
imes, indica ed by dashed lines (Fig. 1). The DSC measu emen s
e ealed a con inuous s abiliza ion o he SCL om ini ially no
isible T
g
due o he o ma ion o he I-phase o a b oad SCLR o 72 K
Fig. 7. Schema ic isualiza ion o a s abilized and des abilized ISRO. The le and igh side depic s exempla ily he s uc u e o an alloy wi h an inc eased and dec eased numbe
o icosahed al mo i s, espec i ely.
L.M. Ruschel, B. Adam, O. G oss e al. Jou nal o Alloys and Compounds 960 (2023) 170614
9