en opy
Le e
Ni ogen In e s i ial Alloying o CoC FeMnNi High
En opy Alloy h ough Reac i e Powde Milling
Igo Mo a cik 1,*, Jan Cizek 2, La issa de Almeida Gou ea 1, Jan Cupe a 1, I an Guban 1and
I o Dlouhy 1
1Ins i u e o Ma e ials Science and Enginee ing, NETME Cen e, B no Uni e si y o Technology,
Technicka 2896/2, 616 69 B no, Czech Republic; gou ea@ u b .cz (L.d.A.G.); [email p o ec ed].cz (J.C.);
[email p o ec ed].cz (I.G.); [email p o ec ed].cz (I.D.)
2Ins i u e o Plasma Physics, The Czech Academy o Sciences, Za Slo ankou 1782/3, 182 00 P ague 8,
Czech Republic; [email p o ec ed]
*Co espondence: igo .mo a cik@ u b .cz; Tel.: +420-541-143-100
Recei ed: 7 Ma ch 2019; Accep ed: 3 Ap il 2019; Published: 4 Ap il 2019


Abs ac :
The p esen wo k is ocused on he syn hesis o CoC FeMnNi high en opy alloy (HEA)
in e s i ially alloyed wi h ni ogen ia powde me allu gy ou es. Using a simple me hod, ni ogen
was in oduced o he HEA om he p o ec i e N
2
gas a mosphe e du ing mechanical alloying (MA)
p ocessing. The la ice pa ame e and amoun o ni ogen in HEA we e obse ed o be linea ly
p opo ional o he milling du a ion. The limi ed solubili y o ni ogen in he main ace cen e ed
cubic (FCC) phase esul ed in he in-si u o ma ion o ni ides and, acco dingly, signi ican inc ease in
he ha dness alues. I has been shown ha ab ica ion o such ni ogen-doped HEA bulk ma e ials
can be con enien ly achie ed by a simple combina ion o MA + spa k plasma sin e ing p ocesses,
wi hou he need o adding ni ogen om o he sou ces.
Keywo ds: me allu gy; in e s i ial; mic os uc u e; powde echnology; mul i-p incipal elemen alloys
1. In oduc ion
The need o sa e y c i ical applica ion ma e ials wi h imp o ed combina ion o high s eng h,
low densi y, and high ac u e esis ance has been s imula ing esea ch e o s o decades [
1
]. La ely,
high en opy alloys (HEA) consis ing o se e al subs i u ional elemen s a nea -equia omic a ios, as
well as composi es de i ed om hem ha e been de eloped [
2
–
4
]. These de ia ed om he es ablished,
single elemen -based alloy designs and possessed a combina ion o p omising p ope ies. I is belie ed
ha such p ope ies a e mos ly gene a ed by an ex eme subs i u ional s eng hening, a ising om
he p esence o mul iple elemen s wi hin a single solid solu ion la ice, he eby e ec i ely inc easing
he e ec i e la ice ic ion s ess [
5
,
6
]. Recen ly, i has been p o en ha he in oduc ion o in e s i ial
elemen s o HEA la ices p omo ed u he signi ican s eng hening. Impo an ly, his is done wi hou
sac i icing duc ili y in he p ocess, hus u he pushing he eminen bo de s o he s eng h-duc ili y
ade-o [
7
–
10
]. While mos a emp s bene i ed om he e ec s o in e s i ial ca bon o bo on, o
da e, only one s udy has been eco ded o success ully apply ni ogen alloying [
11
]. This is a he
su p ising as ni ogen is one o he mos impo an in e s i ial alloying elemen s in aus eni ic s ainless
s eels and CoC bio-compa ible alloys, ha ing a mo e p onounced e ec compa ed o e en ca bon o
bo on, which a e mo e suscep ible o he o ma ion o b i le phases [
12
–
14
]. Pa ially, he lack o high
ni ogen-doped HEA ab ica ed by adi ional me allu gy ou es can be explained by hei complica ed
p oduc ion, as a dissolu ion o high concen a ions o ni ogen in he mol en me al equi es he use o a
high p essu e me allu gy [
15
]. In ou s udy, he in e s i ial ni ogen-doped HEA p oduced by a no el
manu ac u ing ou e is p esen ed. In he p oduc ion, an economical me hod o in oducing in e s i ial
En opy 2019,21, 363; doi:10.3390/e21040363 www.mdpi.com/jou nal/en opy
En opy 2019,21, 363 2 o 7
ni ogen om gas a mosphe e du ing he eac i e powde milling p ocess has been u ilized. A simple
change o he milling a mosphe e om A o N
2
gas esul ed in he inc ease in ha dness alues by 28%.
2. Ma e ials and Me hods
A se o CoC FeMnNi (in equimola p opo ions) HEA powde s we e p epa ed by ball milling
o elemen al powde s wi h pu i y o e 99.5% and a e age pa icle sizes app oxima ely 45
µ
m.
The powde s we e sealed in o a s eel milling bowl con aining 15 mm diame e milling balls wi h he
ball- o-powde weigh a io (BPR) o 10:1. The used milling speed was 300 e olu ions-pe -minu e
o all powde s. To al milling du a ions o 12, 16, and 24 h wi h N
2
a mosphe e and 16, 20, and 24 h
wi h A gas as a e e ence a mosphe e ha e been pe o med, wi hou he use o any p ocess con ol
agen . E e y 30 min, he milling was s opped o 15 min o p e en o e hea ing o he milling bowl
( he p o ided milling imes deno e o al milling ime only, excluding he s op ime pe iods). A he
end o e e y d y milling du a ion, all powde s we e addi ionally we milled o 15 min in e hanol
and subsequen ly d ied in an ai o en a 60
◦
C o inc ease powde yield. The milling condi ions
we e selec ed o e alua e he in luence o milling ime and en i onmen on he chemical composi ion
and ha dness o he powde s, and subsequen ly spa k plasma sin e ing (SPS)-consolida ed inal
bulks. To explo e an al e na i e ou e o ni ogen inco po a ion, ano he powde was milled o
24 h unde A gas a mosphe e, his ime wi h added C
2
N powde pa icles. The amoun o added
C
2
N co esponded o 2 a % o ni ogen (0.48 w %) in he alloy. All milled powde s we e hen
consolida ed by spa k plasma sin e ing (SPS; The mal Technology LSS 10-4) in a 20 mm g aphi e
die. A sin e ing empe a u e o 1150
◦
C wi h 30 MPa p essu e and 8 min holding ime we e used.
G aphi e oils wi h applied BN coa ing we e placed be ween he powde s and he die walls o p e en
con amina ion. The milled powde s and compac ed bulk ma e ials we e p epa ed o mic os uc u al
obse a ions using s anda d me allog aphic g inding and polishing me hods, wi h las s ep pe o med
using mechano-chemical polishing using colloidal silica (S ue s OPS). Fo he analyses, SEM (ZEISS
Ul a Plus, Ca l Zeiss AG, Obe kochen, Ge many) equipped wi h ene gy dispe si e mic oanalysis
(EDS) and elec on backsca e ed di ac ion (EBSD) de ec o s was used. XRD (Philips X
´
Pe , 40 kV, Co
K
α
adia ion a
λ
= 1.7903 Å, 2
θ
= 30–120
◦
, (Philips, Eindho en, The Ne he lands) was used o obse e
phase composi ions a he indi idual p ocessing s eps. The chemical composi ion o he powde s
(including he ni ogen concen a ions) was de e mined using LECO THC-600 spec ome e (LECO
co., S . Joseph, MI, USA). Vicke s mic o-ha dness measu emen o he SPS-ed bulks was ca ied ou
using LECO LM 247AT mic oha dness es e (LECO co., S . Joseph, MI, USA) a a300 g load o ce and
10 s holding ime. THERMOCALC so wa e e sion 2018 (The mo-Calc So wa e AB, Solna, Sweden)
was used o calcula e he phase composi ion p edic ion. Un o una ely, he cu en ly de eloped HEA
da abase (TCHEA1) could no be used as i does no in ol e in e s i ial elemen s, and i s accu acy was
ques ioned [
16
]. As such, THERMOCALC calcula ions we e ealized using an Ni-based alloy da abase
(TCNI9) ins ead.
3. Resul s and Discussion
The calcula ed pseudo-bina y phase diag am o an N-alloyed CoC FeMnNi alloy is p esen ed
in Figu e 1. Among he p esen elemen s, C had he highes a ini y owa ds ni ogen, esul ing
in he appea ance o a C
2
N phase du ing he eu ec ic eac ion. The highes solubili y o N was
~0.5 a % (0.12 w %) a he eu ec ic empe a u e o ~1280
◦
C, dec easing apidly wi h dec easing
empe a u es he ea e .
En opy 2019,21, 363 3 o 7
En opy 2019, 21, x 3 o 7
Figu e 1. Calcula ed pseudo-bina y CoC FeMnNi-N phase diag am showing solubili y changes o N
in he alloy’s main FCC phase wi h empe a u e. Fo ma ion o C
2
N phase can be expec ed o
concen a ions exceeding 0.1 a %.
Alloy mic os uc u es p epa ed using SPS om he powde s subjec ed o 24 h o milling in A
and N
2
a mosphe es a e p esen ed in Figu e 2a,c and 2b,d, espec i ely. In all cases, ully-dense bulk
samples we e ob ained, jus i ying he selec ion o SPS pa ame e s. The mic os uc u e o pu e
CoC FeMnNi alloy is composed o single FCC phase g ains and ine i able oxide inclusions, isible
as ine da k and b igh pa icle dispe sion. The di e ence in he oxide pa icle con as is gi en by
ela i e di e ences in hei chemical composi ion: while he da k pa icles shown in Figu e 2c,d a e
mos ly composed o ch omium and manganese oxides, he whi e pa icles a e also oxides. Howe e ,
hei spec a indica e a signi ican ly lowe oxygen con en (12 a % s. 33 a %) and highe quan i ies
o he h ee hea ie me allic elemen s (Fe, Co, Ni; see he spec a and espec i e composi ions
p o ided in Figu e 3). Bo h dec eased oxide con en and he highe p esence o he h ee hea ie
elemen s igge ed he isible colo di e ence. I should be no ed ha he EDS me hod is no pe ec ly
sui ed o de e mining ligh elemen s such as N o O, and he p esen ed esul s a e he e o e no
mean o ep esen an exac quan i ica ion. The da k shea h isible a ound he whi e-con as oxides
in Figu e 2c pa icles is an e ec caused by he used mechano-chemical polishing (ha d and esis an
C - and Mn- ich oxide pa icles a e p o uding om he ma ix ha was pa ially e ched away).
Impo an ly, he CoC FeMnNi-N bulk alloy p oduced om powde s wi h 0.2 w % o N con ained
addi ional, in e g anula C - and N- ich phases (con i med by EDS, see Figu e 3). This phase
co esponds o a C
2
N ni ide phase om he calcula ed p edic ion in Figu e 1. As his phase was no
obse ed (XRD, EDS) in he powde p io o he SPS p ocess, i s p esence is connec ed o he
dec easing solubili y o ni ogen in he FCC ma ix upon slow cooling a e sin e ing. This p o ided
su icien ime o he nuclea ion o C
2
N g ains a he main FCC phase g ain bounda ies (pa hways
o elemen al di usion). The EBSD o ien a ion maps (Figu e 2e, ) demons a ed ha a e he SPS
p ocess, mic os uc u es we e ully eco e ed, indica ed by a single-colo (single c ys allog aphic
o ien a ion) ep esen a ion o each g ain (should plas ic s ain be s ill p esen a e he SPS, di e en
shades o he indi idual colo s would be isible wi hin each g ain). Pu e CoC FeMnNi and
CoC FeMnNi-N alloys possessed almos iden ical a e age g ain size o he main FCC phase,
quan i ied using he EBSD me hod o be 3.78 ± 1.16 µm and 3.53 ± 1.05 µm, espec i ely. The iden ical
a e age g ain sizes (conside ing gi en unce ain y) despi e he p esence o in e g anula C
2
N in he
CoC FeMnNi-N bulk alloy u he suppo s he hypo hesis on he ni ide p ecipi a ion only du ing
he cooling pe iod om he SPS consolida ion empe a u es. In heo y, an ea lie o ma ion o ni ide
( ha is, du ing he powde milling o i s hal o he SPS sin e ing p ocess) would ha e ac ually
p e en ed g ain g ow h o he CoC FeMnNi-N ma e ial. This would necessa ily ha e esul ed in a
la ge di e ence in he a e age g ain sizes be ween bo h alloys. Howe e , his was no con i med
Figu e 1.
Calcula ed pseudo-bina y CoC FeMnNi-N phase diag am showing solubili y changes o
N in he alloy’s main FCC phase wi h empe a u e. Fo ma ion o C
2
N phase can be expec ed o
concen a ions exceeding 0.1 a %.
Alloy mic os uc u es p epa ed using SPS om he powde s subjec ed o 24 h o milling in A
and N
2
a mosphe es a e p esen ed in Figu e 2a–d, espec i ely. In all cases, ully-dense bulk samples
we e ob ained, jus i ying he selec ion o SPS pa ame e s. The mic os uc u e o pu e CoC FeMnNi
alloy is composed o single FCC phase g ains and ine i able oxide inclusions, isible as ine da k and
b igh pa icle dispe sion. The di e ence in he oxide pa icle con as is gi en by ela i e di e ences
in hei chemical composi ion: while he da k pa icles shown in Figu e 2c,d a e mos ly composed
o ch omium and manganese oxides, he whi e pa icles a e also oxides. Howe e , hei spec a
indica e a signi ican ly lowe oxygen con en (12 a % s. 33 a %) and highe quan i ies o he
h ee hea ie me allic elemen s (Fe, Co, Ni; see he spec a and espec i e composi ions p o ided
in Figu e 3). Bo h dec eased oxide con en and he highe p esence o he h ee hea ie elemen s
igge ed he isible colo di e ence. I should be no ed ha he EDS me hod is no pe ec ly sui ed
o de e mining ligh elemen s such as N o O, and he p esen ed esul s a e he e o e no mean o
ep esen an exac quan i ica ion. The da k shea h isible a ound he whi e-con as oxides in Figu e 2c
pa icles is an e ec caused by he used mechano-chemical polishing (ha d and esis an C - and
Mn- ich oxide pa icles a e p o uding om he ma ix ha was pa ially e ched away). Impo an ly,
he CoC FeMnNi-N bulk alloy p oduced om powde s wi h 0.2 w % o N con ained addi ional,
in e g anula C - and N- ich phases (con i med by EDS, see Figu e 3). This phase co esponds o a
C
2
N ni ide phase om he calcula ed p edic ion in Figu e 1. As his phase was no obse ed (XRD,
EDS) in he powde p io o he SPS p ocess, i s p esence is connec ed o he dec easing solubili y o
ni ogen in he FCC ma ix upon slow cooling a e sin e ing. This p o ided su icien ime o he
nuclea ion o C
2
N g ains a he main FCC phase g ain bounda ies (pa hways o elemen al di usion).
The EBSD o ien a ion maps (Figu e 2e, ) demons a ed ha a e he SPS p ocess, mic os uc u es we e
ully eco e ed, indica ed by a single-colo (single c ys allog aphic o ien a ion) ep esen a ion o each
g ain (should plas ic s ain be s ill p esen a e he SPS, di e en shades o he indi idual colo s would
be isible wi hin each g ain). Pu e CoC FeMnNi and CoC FeMnNi-N alloys possessed almos iden ical
a e age g ain size o he main FCC phase, quan i ied using he EBSD me hod o be 3.78
±
1.16
µ
m
and 3.53
±
1.05
µ
m, espec i ely. The iden ical a e age g ain sizes (conside ing gi en unce ain y)
despi e he p esence o in e g anula C
2
N in he CoC FeMnNi-N bulk alloy u he suppo s he
hypo hesis on he ni ide p ecipi a ion only du ing he cooling pe iod om he SPS consolida ion
empe a u es. In heo y, an ea lie o ma ion o ni ide ( ha is, du ing he powde milling o i s
hal o he SPS sin e ing p ocess) would ha e ac ually p e en ed g ain g ow h o he CoC FeMnNi-N
En opy 2019,21, 363 4 o 7
ma e ial. This would necessa ily ha e esul ed in a la ge di e ence in he a e age g ain sizes be ween
bo h alloys. Howe e , his was no con i med expe imen ally (no e he wo alues o g ain size a e
no s a is ically di e en conside ing he sca e alues), which poin s o he ac ha ni ides o med
du ing he inal SPS cooling phase only.
En opy 2019, 21, x 4 o 7
expe imen ally (no e he wo alues o g ain size a e no s a is ically di e en conside ing he sca e
alues), which poin s o he ac ha ni ides o med du ing he inal SPS cooling phase only.
Figu e 2. The mic os uc u e and EBSD g ain o ien a ion maps o he p oduced alloys, wi h e e ence
di ec ion pe pendicula o he SPS compac ion di ec ion. Pu e CoC FeMnNi alloy p esen ed on he
le hand side in (a), (c), and (e); CoC FeMnNiN alloy p esen ed on igh hand side in (b), (d), and ( )
wi h he o med C
2
N phase deno ed by yellow a ow in (b). Ine i able oxide pa icles a e highligh ed
by ed a ows in (c) and (d).
Figu e 2.
The mic os uc u e and EBSD g ain o ien a ion maps o he p oduced alloys, wi h e e ence
di ec ion pe pendicula o he SPS compac ion di ec ion. Pu e CoC FeMnNi alloy p esen ed on he le
hand side in (
a
,
c
,
e
); CoC FeMnNiN alloy p esen ed on igh hand side in (
b
,
d
,
) wi h he o med C
2
N
phase deno ed by yellow a ow in (
b
). Ine i able oxide pa icles a e highligh ed by ed a ows in (
c
,
d
).
En opy 2019,21, 363 5 o 7
En opy 2019, 21, x 5 o 7
Figu e 3. The ep esen a i e poin EDS spec a aken om he espec i e phases p esen in he
mic os uc u es o SPS-ed bulks o CoC FeMnNi and CoC FeMnNiN: ma ix, whi e-con as C - and
Mn- ich oxides, da k-con as oxides, and he in e g anula C 2N g ains. No e ha conside ing he
in e ac ion olume’s size o he inciden elec on beam and he espec i e size o he oxide pa icles
and ni ide g ains (gene ally below 1µm), he esul s a e no accu a e in e ms o exac quan i ica ion.
The ca bon peaks p esen in all pa e ns a e a consequence o he sample p epa a ion.
In luences o powde milling ime and used a mosphe e on he chemical composi ion (ni ogen
con en ), main FCC phase la ice pa ame e o he p oduced powde s, and ha dness o he bulk
samples a e consolida ion, a e p esen ed in Figu e 4. Milling in ni ogen a mosphe e caused
adso p ion o N a oms a he powde pa icle su aces, and i s subsequen dissolu ion in o he
pa icles, which esul ed in a signi ican inc ease in ni ogen concen a ion wi hin he compac s. The
pe o med XRD analysis e ealed ha all he powde ma e ials and he bulks we e composed o a
single FCC phase. The la ice pa ame e s o he phase we e ound by inc easing wi h he inc easing
N concen a ions in he powde s. The obse a ion is in good ag eemen wi h p e ious esul s s a ing
ha la ice pa ame e s inc ease by in e s i ial alloying [7, 17]. Un o una ely, olume ac ion o he
C
2
N and mino oxide phases was insu icien o enable hei de ec ion by XRD. The co esponding
la ice pa ame e s o SPS compac ed bulks o CoC FeMnNi and CoC FeMnNi-N alloys we e 3.600
and 3.606 Å, espec i ely (no displayed in Figu e 4). Despi e C
2
N phase o ma ion, his esul would
sugges ha a ce ain con en o ni ogen emained dissol ed in he FCC solid solu ion o he
CoC FeMnNi-N bulk. Figu e 4 shows ha he in oduc ion o N esul ed in he inc ease o SPS-ed
ma e ials’ ha dness by ~28% compa ed o he unalloyed coun e pa s. Such inc ease is mos ly
induced by C
2
N phase o ma ion, i.e., seconda y phase dispe sion s eng hening. The (small)
di e ence in la ice pa ame e s o bulk CoC FeMnNi and CoC FeMnNi-N alloys u he sugges s
ha he ha dness inc ease could ha e been pa ially caused by in e s i ial solid solu ion
s eng hening, oo [18,19]. Compa ing ni ogen bulks alloyed om milling in N
2
gas a mosphe e wi h
he co esponding alloy p oduced (using iden ical pa ame e s) unde A a mosphe e by adding C
2
N
powde , i was shown ha he la e exhibi ed ~4% lowe ha dness alues. Such esul is su p ising,
especially conside ing he o al in oduced ni ogen concen a ions (0.2 w % o gas-in oduced N
Figu e 3.
The ep esen a i e poin EDS spec a aken om he espec i e phases p esen in he
mic os uc u es o SPS-ed bulks o CoC FeMnNi and CoC FeMnNiN: ma ix, whi e-con as C - and
Mn- ich oxides, da k-con as oxides, and he in e g anula C
2
N g ains. No e ha conside ing he
in e ac ion olume’s size o he inciden elec on beam and he espec i e size o he oxide pa icles
and ni ide g ains (gene ally below 1
µ
m), he esul s a e no accu a e in e ms o exac quan i ica ion.
The ca bon peaks p esen in all pa e ns a e a consequence o he sample p epa a ion.
In luences o powde milling ime and used a mosphe e on he chemical composi ion (ni ogen
con en ), main FCC phase la ice pa ame e o he p oduced powde s, and ha dness o he bulk samples
a e consolida ion, a e p esen ed in Figu e 4. Milling in ni ogen a mosphe e caused adso p ion o N
a oms a he powde pa icle su aces, and i s subsequen dissolu ion in o he pa icles, which esul ed
in a signi ican inc ease in ni ogen concen a ion wi hin he compac s. The pe o med XRD analysis
e ealed ha all he powde ma e ials and he bulks we e composed o a single FCC phase. The la ice
pa ame e s o he phase we e ound by inc easing wi h he inc easing N concen a ions in he powde s.
The obse a ion is in good ag eemen wi h p e ious esul s s a ing ha la ice pa ame e s inc ease by
in e s i ial alloying [
7
,
17
]. Un o una ely, olume ac ion o he C
2
N and mino oxide phases was
insu icien o enable hei de ec ion by XRD. The co esponding la ice pa ame e s o SPS compac ed
bulks o CoC FeMnNi and CoC FeMnNi-N alloys we e 3.600 and 3.606 Å, espec i ely (no displayed
in Figu e 4). Despi e C
2
N phase o ma ion, his esul would sugges ha a ce ain con en o ni ogen
emained dissol ed in he FCC solid solu ion o he CoC FeMnNi-N bulk. Figu e 4shows ha he
in oduc ion o N esul ed in he inc ease o SPS-ed ma e ials’ ha dness by ~28% compa ed o he
unalloyed coun e pa s. Such inc ease is mos ly induced by C
2
N phase o ma ion, i.e., seconda y
phase dispe sion s eng hening. The (small) di e ence in la ice pa ame e s o bulk CoC FeMnNi and
CoC FeMnNi-N alloys u he sugges s ha he ha dness inc ease could ha e been pa ially caused by
in e s i ial solid solu ion s eng hening, oo [
18
,
19
]. Compa ing ni ogen bulks alloyed om milling
in N
2
gas a mosphe e wi h he co esponding alloy p oduced (using iden ical pa ame e s) unde

En opy 2019,21, 363 6 o 7
A a mosphe e by adding C
2
N powde , i was shown ha he la e exhibi ed ~4% lowe ha dness
alues. Such esul is su p ising, especially conside ing he o al in oduced ni ogen concen a ions
(0.2 w % o gas-in oduced N s. 0.38 w % o C
2
N pa icles-in oduced N p esen in he powde s
a e milling). This is mos likely a consequence o he signi ican ly smalle sizes o (in-si u o med)
C
2
N pa icles in he gas-alloyed bulk, igge ing highe s eng hening e iciency, despi e i s lowe
o al olume. I is in e es ing o poin ou ha he concen a ion o N in oduced o powde s p io o
milling in he o m o added C
2
N pa icles (0.48 w %) is di e en om ha measu ed in he alloyed
powde s a e he milling p ocedu e (0.38 w %). The di e ence could be a ibu ed o C
2
N phase
decomposi ion du ing milling. In summa y, he in oduc ion o ni ogen is achie ed easily by simple
milling in he N
2
gas a mosphe e a e ela i ely sho milling du a ions al eady. Such milling p ocess
does no equi e any addi ional s eps.
En opy 2019, 21, x 6 o 7
s. 0.38 w % o C
2
N pa icles-in oduced N p esen in he powde s a e milling). This is mos likely
a consequence o he signi ican ly smalle sizes o (in-si u o med) C
2
N pa icles in he gas-alloyed
bulk, igge ing highe s eng hening e iciency, despi e i s lowe o al olume. I is in e es ing o
poin ou ha he concen a ion o N in oduced o powde s p io o milling in he o m o added
C
2
N pa icles (0.48 w %) is di e en om ha measu ed in he alloyed powde s a e he milling
p ocedu e (0.38 w %). The di e ence could be a ibu ed o C
2
N phase decomposi ion du ing
milling. In summa y, he in oduc ion o ni ogen is achie ed easily by simple milling in he N
2
gas
a mosphe e a e ela i ely sho milling du a ions al eady. Such milling p ocess does no equi e
any addi ional s eps.
Figu e 4. The in luence o milling ime and eac i e a mosphe e on he o al measu ed ni ogen
con en in he powde s, co esponding la ice pa ame e s o he powde s, and esul ing ha dness o
he SPS compac ed bulks a e sin e ing; A and N se ies e e o powde s milled unde A and N
a mosphe es, espec i ely.
4. Conclusions
In his wo k, we ocus on he p oduc ion o in e s i ial CoC FeMnNi-N high en opy alloys ia
simple and economical me hod o eac i e milling o elemen al powde s in ni ogen a mosphe e. The
main esul s o he s udy can be summa ized as ollows:
• As opposed o me allu gical ou es, ni ogen can be easily in oduced in o CoC FeMnNi
alloy powde s by eac i e mechanical milling in N
2
a mosphe e.
• Ni ogen con en in he inal p oduc s can be adjus ed by al e ing he milling du a ion.
• Due o a limi ed solubili y o ni ogen in he FCC solid solu ion phase, o ma ion o
addi ional C
2
N ni ide phases upon sin e ing is obse ed a highe ni ogen concen a ions
• The in oduc ion o ni ogen in o he CoC FeMnNi HEA esul s in imp o ed ha dness by
combining he second phase dispe sion and solid solu ion in e s i ial s eng hening e ec s.
Au ho Con ibu ions: concep ualiza ion, I.M., J.C. (Jan Cizek); me hodology, I.M., J.C. (Jan Cizek), J.C. (Jan
Cupe a), I.G.; so wa e, L.d.A.G.; o mal analysis, I.M., J.C. (Jan Cizek), I.D.; in es iga ion, I.M., J.C. (Jan Cizek);
esou ces, I.D.; w i ing—o iginal d a p epa a ion, I.M., J.C. (Jan Cizek); w i ing—L.d.A.G., J.C. (Jan Cizek).
Funding: The au ho s g a e ully acknowledge he inancial suppo p o ided by he ESIF, EU p ojec
“A chi ec u ed Ma e ials Designed o Addi i e Manu ac u ing”, Reg. No. CZ.02.1.01/0.0/0.0/16_025/0007304
and also he suppo om p ojec o Czech Science Founda ion Reg. No. 19-220 16S.
Figu e 4.
The in luence o milling ime and eac i e a mosphe e on he o al measu ed ni ogen
con en in he powde s, co esponding la ice pa ame e s o he powde s, and esul ing ha dness o
he SPS compac ed bulks a e sin e ing; A and N se ies e e o powde s milled unde A and N
a mosphe es, espec i ely.
4. Conclusions
In his wo k, we ocus on he p oduc ion o in e s i ial CoC FeMnNi-N high en opy alloys ia
simple and economical me hod o eac i e milling o elemen al powde s in ni ogen a mosphe e.
The main esul s o he s udy can be summa ized as ollows:
•
As opposed o me allu gical ou es, ni ogen can be easily in oduced in o CoC FeMnNi alloy
powde s by eac i e mechanical milling in N2a mosphe e.
•Ni ogen con en in he inal p oduc s can be adjus ed by al e ing he milling du a ion.
•
Due o a limi ed solubili y o ni ogen in he FCC solid solu ion phase, o ma ion o addi ional
C 2N ni ide phases upon sin e ing is obse ed a highe ni ogen concen a ions
•
The in oduc ion o ni ogen in o he CoC FeMnNi HEA esul s in imp o ed ha dness by
combining he second phase dispe sion and solid solu ion in e s i ial s eng hening e ec s.
Au ho Con ibu ions:
Concep ualiza ion, I.M., J.C. (Jan Cizek); me hodology, I.M., J.C. (Jan Cizek), J.C.
(Jan Cupe a), I.G.; so wa e, L.d.A.G.; o mal analysis, I.M., J.C. (Jan Cizek), I.D.; in es iga ion, I.M., J.C. (Jan Cizek);
esou ces, I.D.; w i ing—o iginal d a p epa a ion, I.M., J.C. (Jan Cizek); w i ing—L.d.A.G., J.C. (Jan Cizek).
En opy 2019,21, 363 7 o 7
Funding:
The au ho s g a e ully acknowledge he inancial suppo p o ided by he ESIF, EU p ojec
“A chi ec u ed Ma e ials Designed o Addi i e Manu ac u ing”, Reg. No. CZ.02.1.01/0.0/0.0/16_025/0007304
and also he suppo om p ojec o Czech Science Founda ion Reg. No. 19-220 16S.
Con lic s o In e es : The au ho s decla e no con lic o in e es .
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