In luence o deposi ion s a egy and hea ea men on mechanical
p ope ies and mic os uc u e o 2319 aluminium WAAM componen s
Maide A ana
a,b,
⇑
, Eneko Uka
b
, Ike Rod iguez
a
, Da id Aguila
a
, Ped o Ál a ez
a
a
LORTEK Technological Cen e, Basque Resea ch and Technology Alliance (BRTA), O dizia, Spain
b
Mechanical Enginee ing Depa men , Uni e si y o he Basque Coun y UPV/EHU, 48013 Bilbao, Spain
highligh s
WAAM o 2319 aluminium alloy is
in es iga ed.
Deposi ion s a egy, geome y and
hea ea men a ec s mechanical
p ope ies.
Wi hou in e laye dwell ime, ine
equiaxed mic os uc u e is ob ained.
Low aniso opy is achie ed i p ope
a i icial aging is applied.
g aphical abs ac
a icle in o
A icle his o y:
Recei ed 22 Ma ch 2022
Re ised 11 July 2022
Accep ed 20 July 2022
A ailable online 25 July 2022
Keywo ds:
WAAM
Aluminium
Mechanical p ope ies
Hea ea men
Mic os uc u e
Aniso opy
abs ac
The e is an inc easing in e es in addi i e manu ac u ing o high s eng h aluminium alloys buil wi h
wi e and a c addi i e manu ac u ing (WAAM) echnologies. Al-Cu alloys a e suscep ible o ho c acking,
howe e , pulse ad anced cold me al ans e (CMT-PADV) welding p ocess ensu es a low hea inpu ha
a oids his de ec while educing he pa po osi y. This s udy has demons a ed ha po osi y below 1 %
does no a ec mechanical p ope ies o 2319 WAAM walls, whe eas he as-buil mic os uc u e and
applied hea ea men highly in luence he p ope ies ob ained. Wi hou in e laye dwell ime, a ine
uni o mly dis ibu ed equiaxed mic os uc u e is ob ained, howe e , i an in e laye a c s op pe iod is
applied, columna dend i ic g ains in he in e laye zone is ob ained. Hea ea men wi h low aging em-
pe a u e and ime demons a ed no o be sui able o ensu e high mechanical p ope ies and low aniso-
opy. Ins ead, i 190 °C and 26-hou aging hea ea men is used, p ope ies up o 324 MPa o yield
s ess, 452 MPa ensile s eng h and 8 % elonga ion can be achie ed pe pendicula ly o he building di ec-
ion wi h aniso opy o 1 %, 2 % and 46 %, espec i ely, o he manu ac u ing condi ions ha a oided
columna g ains. This ac was c i ical o ensu e highes s eng h and duc ili y alues and low aniso opy.
Ó2022 The Au ho s. Published by Else ie L d. Thisisanopenaccessa icleunde heCCBY-NC-NDlicense
(h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/).
1. In oduc ion
Wi e and A c Addi i e Manu ac u ing (WAAM) is de ined as a
p ocess by which me allic pa s can be manu ac u ed supe posi-
ioning welding beads, laye by laye . I is classi ied in o he ca e-
go y o di ec ed ene gy deposi ion (DED) p ocesses and as he
h ps://doi.o g/10.1016/j.ma des.2022.110974
0264-1275/Ó2022 The Au ho s. Published by Else ie L d.
This is an open access a icle unde he CC BY-NC-ND license (h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/).
⇑
Co esponding au ho a : LORTEK Technological Cen e, Basque Resea ch and
Technology Alliance (BRTA), O dizia, Spain.
E-mail add ess: [email p o ec ed] (M. A ana).
Ma e ials & Design 221 (2022) 110974
Con en s lis s a ailable a ScienceDi ec
Ma e ials & Design
jou nal homepage: www.else ie .com/loca e/ma des
name desc ibes, and elec ic a c powe ed om a welding sou ce is
employed o mel and deposi wi e shaped eeds ock [1–3].
WAAM is well sui ed o he manu ac u ing o medium o la ge
size componen s due o he high deposi ion a es (usually om 2
o 4 Kg/h), supe io ma e ial usage (>90 %), ou s anding ene gy
e iciencies (be ween 85 and 90 %) and scalable wo king en i on-
men . S udies ha e shown ha WAAM p ocess can educe manu-
ac u ing cos om 7 % o 69 % compa ed o con en ional
sub ac i e p ocesses such as machining [4]. In ac , WAAM is cu -
en ly conside ed as he me al addi i e manu ac u ing p ocess
wi h he lowes cos and en i onmen al impac pe kg o deposi ed
ma e ial [5]. The e o e, his echnology is being se iously consid-
e ed o he epai ing and manu ac u ing o me als componen s
in many sec o s such as ae ospace, na al, ooling, oil and gas and
au omo i e [2].
In o de o a ain igh dimensional ole ances and smoo h su -
ace, WAAM has o be combined wi h sub ac i e echnologies, bu
e en wi h his sub ac i e pos -p ocessing s ep, he buy- o- ly
(BTF) a io can be g ea ly educed in ae ospace componen s like
ings, gea s, ibs, spa s o bulkheads which usually show BTF a ios
abo e 10 o con en ional machining p ocesses [2,6]. Many o
hese componen s a e cu en ly made o high s eng h aluminium
alloys due o hei good mechanical p ope ies, low densi y and
high co osion esis ance. The e o e, in he las yea s he e has
been a g owing in e es owa ds he de elopmen o WAAM o
di e en aluminium alloys, aiming o each mechanical pe o -
mances compa able o w ough and olled 2000 se ies aluminium
alloys ha a e widely used in he ae ospace indus y [7–9].A
ecen summa y o some o he mos ele an wo ks in his ield
can be ound elsewhe e [10]. Mos o he s udies, ha e been ca ied
ou wi h Al-Cu alloys, 2319 speci ically, as his is he only one om
he 2000 se ies which is conside ed eadily weldable, because i
does no su e ho c acking [11].
Me al ine gas (MIG) based WAAM has se e al ad an ages in
compa ison wi h ungs en ine gas (TIG) o plasma a c welding
(PAW) such as he use o consumable elec ode and coaxial eeding
which simpli ies he ool pa h planning and sys em complexi y
[12]. Howe e , con en ional MIG p ocess usually gi es ise o
excessi e hea ing which leads o dis o ion and po osi y in alu-
minium welds. These limi a ions can be minimized by cold me al
ans e (CMT
Ò
) echnology om F onius Company [13], i.e., an
imp o emen o sho -ci cui MIG p ocess wi h educed hea
inpu . In ac , many p e ious wo ks ha e concluded ha CMT is a
compe en manu ac u ing p ocess o WAAM o aluminium
componen s.
Se e al esea ch g oups ha e in es iga ed he e ec o CMT a c
modes o a ian s on he po osi y and mechanical p ope ies o
2xxx (Al-Cu) [8,14–17] and 5xxx (Al-Mg) [18,19] se ies WAAM alu-
minium pa s. The s udied CMT a ian s include con en ional CMT,
CMT pulse (CMT-P), CMT ad anced (CMT-ADV) and CMT pulse
ad anced (CMT-PADV), he la e a combina ion o mechanically
con inuously pushed and pulled wi e eeding mo emen coupled
wi h al e na i ely pola i y shi s which modi y mel ing a e [20].
Acco ding o Fang e al. [21], CMT-PADV based WAAM o 2219
alloy e ec i ely educes po osi y below 1 % educing po e size
below 100
l
m, whe eas an equiaxed g ain s uc u e is ob ained.
As a esul , ou s anding mechanical p ope ies a e ob ained wi h
CMT-PADV a c mode, eaching a e T6 he mal ea men a ensile
s eng h up o 283 MPa and almos iso opic beha iou , wi h only a
di e ence o 5 MPa be ween he e ical and ho izon al ensile
es ing di ec ion.
All p e ious wo ks concluded ha CMT-PADV is he mos sui -
able welding p ocess educing d as ically he po osi y o 2319
WAAM samples. Cong e al. we e pionee s in d awing his conclu-
sion and i was explained by he lowe hea inpu o CMT-PADV
and e ec i e oxide cleaning o he wi e [8].
The in luence o he quali y o aluminium eeds ock wi e has
also been deeply in es iga ed [22,15]. Consis en wi e su ace
quali y and p ope ies a e equi ed o keep s able p ocess s abili y
and o ob ain ines quali y in WAAM samples.
As-buil mechanical p ope ies o 2319 WAAM samples can be
g ea ly enhanced by applying con en ional T6 he mal ea men
a e he comple e manu ac u ing o he pa o by applying olling
o peening a e deposi ion o each laye [7,23,24]. Pa icula ly
pos -deposi ion hea ea men enhances mechanical p ope ies
o alues abo e 300 MPa o yield s ess and 450 MPa o ensile
s eng h. These p ope ies o e come he s anda d speci ica ions
eques ed o equi alen w ough 2219-T6 pla es.
In e pass olling is based on applying comp essi e p essu e on
he op su ace o each laye using a olling ig wi h a hyd aulic
cylinde . Gu e al. [7] s udied he e ec o di e en olling loads
( om 15 kN o 45 kN) and T6 hea ea men [25] in he esul an
mechanical p ope ies o 2319 WAAM pa s. In he as-build condi-
ion, as he load inc eased, he yield s ess (YS) and ensile s eng h
(UTS) inc eased, bu elonga ion was educed. I combined wi h he
T6 ea men , he elonga ion was highly imp o ed. The e o e, o
ob ain he bes mechanical p ope ies ela ion, wi h YS abo e
300 MPa, UTS abo e 450 MPa and elonga ion g ea e han 14 %,
T6 hea ea men was essen ial. By his aging he mal ea men ,
esul ing aniso opy was minimum.
Guo e al. [26] s udied ano he pos welding de o ma ion ech-
nique, lase shock peening. I consis s on applying a pulse lase
wi h high powe densi y and ul a-sho du a ion o induce la ge
dep h and high alue comp essi e esidual s ess. Wi h his ech-
nique, he as-buil yield s ess was imp o ed, almos doubled up
o 178.3 MPa, bu he elonga ion wo sened.
Al-Cu alloys a e hea ea able, bu he in luence o he hea
ea men a e WAAM on mechanical p ope ies and aniso opy
has no been deeply in es iga ed so a . In ac , di e en au ho s
and e en esea che s om he same g oup, ha e applied di e en
he mal ea men s o hese alloys a di e en aging empe a u es
and du ing di e en soaking imes wi hou any de ailed jus i ica-
ion [7 27]. The ASM Handbook [25] es ablishes sui able hea ea -
men s o he di e en aluminium alloys including 2219 w ough
o olled alloy.
In addi ion o he hea ea men , K. F. Aya kwa e al. [27] s ud-
ies he e ec o deposi ion s a egies on mechanical p ope ies o
WAAM samples made o 2319 alloy. They used oscilla ed and pa -
allel deposi ion s a egies along wi h single bead deposi ion. Man-
u ac u ed samples had di e en wall hickness anging om 7 o
11 mm. I was concluded ha he bes mechanical p ope ies a e
ob ained when using single bead deposi ion, ha ing YS o e
300 MPa, UTS o e 450 MPa and elonga ion o e 12 % a e dedi-
ca ed hea ea men . Cong e al. also in es iga ed he e ec o wall
hickness in hin and block s uc u es o 2319 [28]. In gene al, one
can conclude ha deposi ion s a egy, i.e., geome y and o ch
mo emen , plays an impo an ole in he manu ac u e o WAAM
pa s and esul ing mic os uc u e and mechanical p ope ies.
In his s udy, addi ional ec angula deposi ion geome y is
analysed, wi h no in e laye dwell ime, as well as s aigh wall
deposi ions wi h in e laye dwell ime o in es iga e he e ec
o he hea accumula ion in he inal p ope ies. The in luence o
o ch mo emen is also in es iga ed. Addi ionally, he impac o
hea ea men on he mechanical p ope ies is in es iga ed by
analysing he in luence o aging empe a u e and ime o di e en
deposi ion s a egies.
2. Ma e ials and me hods
To manu ac u e he pa s o be analysed in his s udy, a pulse
ad anced cold me al ans e (CMT-PADV)-based WAAM p ocess
M. A ana, E. Uka , I. Rod iguez e al. Ma e ials & Design 221 (2022) 110974
2
wi h ER2319 ille me al o 1.2 mm diame e was employed. The
special quali y wi e so-called ‘‘ce i ied p emium Aluminium
2319 wi e” was p o ided by WAAM3D. The chemical composi ion
o he ma e ials used a e shown in Table 1. This ille me al was
deposi ed o e 10 mm hickness AA6082-T6 subs a e using CMT
1369 + P Ad syne gic cu e.
A F onius CMT Ad anced 4000 R welding powe sou ce and RA
5000 22G welding o ch (F onius In e na ional GmbH, Pe enbach,
Aus ia) assembled in a Fanuc ARC Ma e 120iC obo (Fanuc Co po-
a ion, Oshino-mu a, Yamanashi P e ec u e, Japan) we e
employed. The equipmen (Fig. 1) was moun ed in he in elligen
welding cell o LORTEK. Pu e a gon (99.999 %) was used as shield-
ing gas wi h cons an low o 30 L/min. Nozzle o pa wo k dis-
ance was ixed a 12 mm (see Fig. 2).
The p ocess pa ame e s used o manu ac u e he pa s we e
kep cons an h oughou all he s udy: he in ensi y was 96 A, a-
el speed (TS) was 0.6 m/min, and wi e eed speed (WFS) was 6 m/
min. CMT-PADV echnology has an addi ional pa ame e called EP/
EN balance, wi h a ange om 5 o + 5, ha changes he balance
be ween posi i e and nega i e cycles. This pa ame e was kep a
0, excep o he i s laye , whe e in o de o a oid necking de ec
due o hea sinking h ough he subs a e, i was ixed a + 4 and
WFS was inc eased o 10 m/min. As a esul , he hea inpu
inc eased in he i s laye and sh inkage was a oided.
Two deposi ion s a egies in e ms o o ch mo emen we e
selec ed (Fig. 3). Ha ching s a egy, ep esen s a s aigh weld bead
wi hou any wea ing, whe eas in ci cling s a egy, he o ch oscil-
la es o gene a e an o e lap o ound ci cles wi h 1 mm ampli ude
and 2 Hz equency. Fo bo h s a egies, a el di ec ion was chan-
ged om odd o e en laye s o p o ide a s able g ow h.
Two di e en geome ies we e manu ac u ed (Fig. 4). Fi s one,
called ec angula , is a con inuous ec angula spi al, ha does no
ha e a c s ops, he e o e he e is no dwell ime be ween laye . The
o he one is a s aigh wall geome y wi h 90 s dwell ime be ween
laye s. The s aigh wall geome y was s udied o bo h ha ching
and ci cling deposi ion s a egies, whe eas he ec angula was
only manu ac u ed wi h ha ching s a egy.
To analyse he mic os uc u e o he pa s, samples ex ac ed
pe pendicula ly o he base me al we e e ched du ing 20 s wi h
Kelle (95 ml H
2
O + 2.5 ml HNO
3
+ 1.5 ml HCl + 1 ml HF) eagen
and analysed in an Olympus Gx51 mic oscope. Se e al mic o-
g aphs we e also aken in he same mic oscope o de e mine a ea
pe cen age po osi y by ImageJ p og am. The applied me hodology
enabled o quan i y po es g ea e han 10
l
m in diame e .
Fou hea ea men s a e WAAM p ocess we e analysed in his
s udy. Two o hem ha e longe aging ime and highe empe a-
u e, whils he o he wo ha e lowe ones (Fig. 5). Ha dness es s
we e ca ied ou h oughou he ea men a di e en aging imes
(Fig. 5). To do so, an EMCO-TEST Du ascan 20 mic o-du ome e
(EMCO-TEST P ü maschinen GmbH, Kuchl, Aus ia) was used. Fi e
measu emen s we e aken om h ee zones o each sample (bo -
om zone 5 mm away om he base me al, middle zone and op
zone).
The dimensions o he s aigh walls we e di e en o ob ain
e ical (90 mm 130 mm) and ho izon al (130 mm 70 mm)
ensile es specimens, whils o he ec angula geome y, ensile
es pa s o bo h loading di ec ions we e ob ained om he same
pa (200 mm 130 mm). Th ee specimens we e ex ac ed om
each s aigh wall and six om he ec angula pa s (3 e ical
ensile es samples and 3 ho izon al ones). They we e ex ac ed
acco ding o he ASTM E8M s anda d om he co e o he walls,
a oiding he a c s a and end egions (Fig. 6).
Table 1
Chemical composi ion o base and ille me als.
Alloy Chemical composi ion (w %)
Al C Cu Fe Mg Mn Si Ti V Zn Z Be
ER2319 Bal. – 6.39 0.115 0.0073 0.274 0.0366 0.136 0.112 0.0095 0.163 0.0001
Al6082-T6 Bal. 0.25 0.1 0.5 0.6 – 1.2 0.4–1 0.7 – 1.3 0.1–– ––
Fig. 1. Manu ac u ing equipmen .
Fig. 2. WAAM p ocess main componen s.
M. A ana, E. Uka , I. Rod iguez e al. Ma e ials & Design 221 (2022) 110974
3
A ZwickRoell Z100 ensile es machine (ZwickRoell GmbH & Co.
KG, UlM, Ge many) was used o ca y ou mechanical es ing. By
es ing h ee samples along wo loading di ec ions ( e ical and
ho izon al) aniso opy was s udied.
3. Resul s
Wi h he applied welding pa ame e s, walls be ween 7 and
11 mm hickness we e ob ained, depending on he geome y and
o ch mo emen . The hickes wall was ob ained o he ec angu-
la geome y wi hou in e pass dwell ime. In addi ion, he o ch
mo emen also in luenced he s aigh wall WAAM pa ’s hick-
ness. As ci cling uses an oscilla ion, he esul an hickness was a
couple mm wide han he one ob ained wi h he ha ching s a -
egy. Thus walls o a ound 7 mm we e ob ained in s aigh wall
geome y o ha ching deposi ion s a egy, whe eas inal a e age
hickness was inc eased o 9 mm o he same geome y bu wi h
ci cling.
By modi ying welding pa ame e s in he i s laye as explained
p e iously, i.e., +4 EP/EN balance, WFS 10 m/min and in ensi y 130
A, he sh inkage o he welding bead was e ec i e a oided as
shown in Fig. 7. This s a egy o adap ing p ocess pa ame e s in
he i s laye o compensa e enhanced hea sinking e ec due o
Fig. 3. To ch mo emen based deposi ion s a egies in he s udy.
Fig. 4. Deposi ion geome ies o he s udy.
Fig. 5. Soak imes o aging ea men a which specimens we e ex ac ed o mic oha dness.
M. A ana, E. Uka , I. Rod iguez e al. Ma e ials & Design 221 (2022) 110974
4
he p oximi y o he ini ially cold subs a e has also been employed
p e iously [19] and i is some hing c i ical in WAAM o aluminium
alloys wi h high he mal conduc i i y. O he au ho s ecommend
o use MIG-P ans e ence mode in he i s laye o 2319 alloy
o a oid c acking in he in e ace and a oid educ ion o he
load-bea ing a ea [17].
3.1. Mic os uc u e o di e en deposi ion s a egies
Each deposi ion geome y ( ec angula o s aigh wall) has a
di e en e ec on hea inpu and he e o e in he esul an
mic os uc u e (Fig. 8). S aigh walls had dend i ic s uc u e and
columna g ains elonga ed along he e ical di ec ion whe eas
equiaxed g ains we e ob ained o he ec angula geome y.
As he ec angula one is a con inuous spi al wi hou welding
p ocess in e up ions, he a c ne e ex inguishes, and as a esul
he pa canno cool down as much as in he s aigh wall geome-
y, wi h 90 s dwell ime be ween consecu i e laye s. Along his
ime he a c is swi ched o and he cumula ed hea is e acua ed
by conduc ion and con ec ion.
The e o e, he lack o dwell ime in ec angula geome y can be
associa ed wi h a dec ease o he e ical componen o he em-
pe a u e g adien due o he mal conduc i i y h ough he p e i-
ously o med laye s o he subs a e, which esul s in equiaxed
g ain mic os uc u e.
In addi ion, he deposi ion s a egy (ha ching o ci cling) also
changes he hea inpu o he p ocess. As du ing ci cling he o ch
goes backwa ds in each oscilla ion, his causes he ehea ing o he
p e iously deposi ed me al inc easing he hea inpu and in oduc-
ing mo e hea . On he con a y, he e is a cons an o wa d mo e-
men o he o ch wi h ha ching, leading o a educ ion o hea
inpu .
In his sense, dimensions o ho izon al and e ical wall con ig-
u a ions (Fig. 6b and c), signi ican ly in luenced esul ing
mic os uc u e. Du ing WAAM o he ho izon al s aigh wall, less
bu longe laye s we e employed compa ed o he e ical s aigh
wall. The e o e, he a c was con inuously igni ed du ing a longe
pe iod o ime o he ho izon al s aigh wall and he pa accumu-
la ed mo e hea esul ing in a dis inc i e g ain mo phology and
mic os uc u e. This e ec can be seen in Fig. 8. Ve ical samples
ha ing mo e e ec i e hea dissipa ion and he e o e, less hea
accumula ion, shown la ge elonga ed columna g ains han he
ones in he ho izon al di ec ion.
Based on he analysis o he mic os uc u e, he hea accumula-
ion o each deposi ion s a egy om he lowes o he highes is as
ollows: s aigh wall – ha ching – e ical, s aigh wall – ci cling
– e ical, s aigh wall – ha ching – ho izon al, s aigh wall – ci -
cling – ho izon al and las ly ec angula – ha ching. As i has been
explained abo e, because o he lack o dwell ime in he ec angu-
la geome y, he e ical empe a u e g adien h ough he p e i-
ously deposi ed laye s will be educed, a ou ing he gene a ion o
ine equiaxed g ains.
Fig. 6. (a) Dimensions o ensile specimens in mm. Schema ic ep esen a ion o he specimens in (b) s aigh wall - e ical, (c) s aigh wall - ho izon al and (d) ec angula
pa s.
Fig. 7. Sh inkage o he i s welding bead a oided in by pa ame e adjus men in
2319 specimen manu ac u ed by WAAM.
M. A ana, E. Uka , I. Rod iguez e al. Ma e ials & Design 221 (2022) 110974
5
3.2. Po osi y
The use o di e en deposi ion s a egies has an impac on he
esul an po osi y o he pa s. I can be seen in he esul s included
in Table 2 ha he e is a di ec ela ionship be ween he hea accu-
mula ion wi h he po osi y. The epo ed po osi y pe cen ages
we e de e mined by measu ing he a ea pe cen age o po es in
se e al mic og aphs.
Table 2
Deposi ion s a egy e ec in he po osi y a ea pe cen age esul s in his s udy.
Sample Po osi y (a ea %) ØMax po e (
l
m)
S aigh wall - Ha ching - Ve ical 0.83 70.12
S aigh wall - Ci cling - Ve ical 0.67 60.38
S aigh wall - Ha ching - Ho izon al 0.47 59.19
S aigh wall - Ci cling - Ho izon al 0.40 76.48
Rec angula 0.84 92.30
Fig. 8. Mic os uc u e mic og aphs o each deposi ion s a egy in as-buil condi ion. (1) S aigh geome y wi h Ha ching deposi ion geome y o ob ain e ical ensile
specimens, (2) S aigh geome y wi h Ci cling deposi ion s a egy o ob ain e ical ensile specimens, (3) S aigh geome y wi h Ha ching deposi ion s a egy o ob ain
ho izon al ensile specimens, (4) S aigh geome y wi h Ci cling deposi ion s a egy o ob ain ho izon al ensile specimens and (5) Rec angula geome y. (a) Mic os uc u al
changes h oughou he laye s, (b) be ween laye zone and (c) wi hin laye zone.
M. A ana, E. Uka , I. Rod iguez e al. Ma e ials & Design 221 (2022) 110974
6
I is wo h men ioning ha he deposi ion s a egies wi h mos
educed hea accumula ion had highe po osi y alues, and his
g adually educes as he hea accumula ion is inc eased, excep
o he ec angula p ocess, which has he highes po osi y once
again (Table 2). Howe e , all he esul s a e below 1 % and he
g ea es po e is smalle han 100
l
m in diame e (Fig. 9).
3.3. Ha dness
Di e en hea ea men s ha e been applied o 2319 WAAM
walls buil wi h di e en deposi ion s a egies and geome ies o
analyse he e olu ion o he ha dness (Fig. 10).
As i can be seen, he e is an e iden e ec o aging empe a u e
in he ha dness o he samples. Samples aged a 175 °C had a ha d-
ness be ween 138 and 152 HV (Fig. 10 le ), whe eas samples ea-
ed a 190 °C shown lowe ha dness alues om 130 o 143 HV
(Fig. 10 igh ). Anyway, a e age alues o he samples ea ed a
175 °C (le hand side in Fig. 10) a e clea ly highe han hose o
ea ed a 190 °C ( igh hand side in Fig. 10). On he con a y, he
deposi ion s a egy and geome y did no clea ly a ec he
ha dness.
3.4. Tensile es
Mechanical p ope ies ob ained om ensile es samples
machined om WAAM walls ea ed a di e en aging condi ions
a e included in Table 3. F om hese da a, one can conclude ha
he deposi ion geome y di ec ly a ec ed he mechanical p ope -
ies. S aigh wall samples shown null duc ili y in e ical di ec ion
a e sho (3–6 h) and low empe a u e (175 °C) aging ea men s.
The e o e, one can conclude ha his sho hea ea men is no
able o dissol e he phases p ecipi a ed in he g ain bounda ies
(Fig. 11), which in ac a e bigge in size han in as-buil s a e.
The combina ion o his phase along g ain bounda ies wi h he
Fig. 9. Po osi y mic og aphs o he di e en deposi ion s a egies: (a) Ha ching - Ve ical, (b) Ci cling - Ve ical, (c) Ha ching - Ho izon al, (d) Ci cling - Ho izon al and (e)
Rec angula .
Fig. 10. Mic oha dness e olu ion along aging ime a 175 °C (le ) and 190 °C ( igh ).
M. A ana, E. Uka , I. Rod iguez e al. Ma e ials & Design 221 (2022) 110974
7
columna g ain s uc u e in e ical di ec ion leads o a p ema u e
ac u e wi hou eaching plas ic de o ma ion.
On he con a y, o 26 h a 190 °C, he o iginal phases in he
g ain bounda ies a e almos dissol ed and he ones emaining
a e smalle in size and sphe ical in shape, no limi ing elonga ion
esul s. The s eng h and elonga ion o he ec angula geome y
– ha ching, a e signi ican ly highe in compa ison wi h s aigh
walls (up o 4 % highe o yield s ess and 5 % o ul ima e ensile
s eng h). Mo eo e , o his pa icula condi ion, i is ema kable
he ac ha he e a e no di e ences in yield s ess and ensile
s eng h be ween e ical and ho izon al o ien a ions, meaning
ha s eng h is e y iso opic. No e ha his WAAM manu ac u -
ing condi ions led o ine and equiaxed g ains in as-buil s a e
(Fig. 8). Samples wi h hese mic os uc u es ga e ise o accep able
mechanical p ope ies e en when sho and low empe a u e aging
ea men s we e applied. Howe e , a be e balance and iso opy
was eached o he long and high he mal ea men .
4. Discussion
In his s udy he in luence o bo h deposi ion s a egy (geome-
y, in e pass dwell ime and o ch mo emen ) and he mal ea -
men o di e en 2319 WAAM geome ies has been in es iga ed.
Table 3
Mechanical p ope ies ob ained in his s udy.
Sample PWHT Ex ac ion Yield S ess Tensile S eng h Elonga ion
Rp
0.2
(MPa) Rm (MPa)
e
%
Rec angula Ha ching 175 °C – 3 h Ve ical 272 ± 1 386 ± 6 5.60 ± 0.1
Ho izon al 283 ± 1 452 ± 3 15.25 ± 2.7
175 °C – 6 h Ve ical 306 ± 4 396 ± 15 3.59 ± 1.1
Ho izon al 303 ± 3 434 ± 3 10.16 ± 1.1
190 °C – 18 h Ve ical 319 ± 2 414 ± 2 4.15 ± 0.4
Ho izon al 322 ± 5 439 ± 4 9.41 ± 0.2
190 °C – 26 h Ve ical 321 ± 2 443 ± 10 6.12 ± 2.3
Ho izon al 324 ± 3 452 ± 1 8.93 ± 0.8
S aigh wall Ha ching 175 °C – 3 h Ve ical 0 163 ± 13 0.00
Ho izon al 287 ± 4 459 ± 14 18.36 ± 0.8
175 °C – 6 h Ve ical 0 251 ± 65 0.08 ± 0.1
Ho izon al 332 ± 8 470 ± 18 9.10 ± 2.1
190 °C – 26 h Ve ical 304 ± 2 405 ± 18 3.09 ± 1.1
Ho izon al 321 ± 8 445 ± 5 8.44 ± 0.8
S aigh wall Ci cling 175 °C – 3 h Ve ical 0 131 ± 14 0.00
Ho izon al 317 ± 10 463 ± 11 14.55 ± 1.3
175 °C – 6 h Ve ical 0 150 ± 16 0.00
Ho izon al 300 ± 8 436 ± 30 7.83 ± 2.9
190 °C – 26 h Ve ical 298 ± 1 415 ± 10 5.45 ± 1.5
Ho izon al 322 ± 8 446 ± 5 8.38 ± 0.8
Fig. 11. Mic os uc u e and phase analysis o specimens h ough hea ea men s o s aigh wall geome y.
M. A ana, E. Uka , I. Rod iguez e al. Ma e ials & Design 221 (2022) 110974
8
The mechanical p ope ies ob ained in his wo k, a e highe
han he ones epo ed in he bibliog aphy o 2319 alloy [7 9 14
26 29 24]. These p e ious wo ks ha e associa ed limi ed mechan-
ical p ope ies and high aniso opy o he ollowing ac o s: po os-
i y, mic os uc u e and hea ea men o p ecipi a ion s a e.
Rega ding po osi y, di e en po osi y le els ha e been epo ed
o his alloy by se e al au ho s. Zhang e al. [14] epo ed po osi y
up o 0.98 % e en o he bes welding condi ion (CMT-PADV),
whils Cong e al. [8] s a ed ha no po es g ea e han 10
l
min
diame e we e ound in a 15 mm ep esen a i e sec ion o pa ,
100 mm in leng h, manu ac u ed wi h CMT-PADV a c mode, how-
e e , no a ea pe cen age po osi y was gi en. As o Fang e al. [24],
po osi y was measu ed by omog aphy and a po osi y olume o
0.46 mm
3
was ob ained.
The in luence o CMT a ian o a c mode in educing po osi y
has been deeply in es iga ed [8] o his alloy. Mo eo e , he e ec
o shielding gas low a e [25] and wi e su ace quali y [15] has
been s udied o Al-Mg alloys. In his s udy, ecommended CMT-
PADV mode and high low a es o 30 L/min ha e been employed
and esul ing po osi y was e icien ly educed o less han 1 %.
Mo eo e , he pa wi h highe po osi y (0.84 a ea %) is he one
wi h g ea es mechanical p ope ies and he lowes aniso opy.
Many au ho s ha e conside ed ha i po es a e aligned and con-
cen a ed in in e laye egions, his can educe and limi he plas ic
s ain capabili y. The e o e, he educed duc ili y de e mined in
samples machined along e ical o ien a ion has been usually
linked wi h his aligned po osi y issue in aluminium WAAM pa s
[18]. Aligned po es educe he e ec i e a ea and ease s ess con-
cen a ion and c ack g owing in his egion. In his ega d, po osi y
obse ed in cu en wo k was andomly dis ibu ed (Fig. 9) and
he e o e, his duc ili y limi ing ac o can be disca ded.
On he o he hand, he mic os uc u al cha ac e isa ion has
demons a ed ha esul ing mic os uc u e g ea ly depends on
he deposi ion s a egy and geome y. The ec angula geome y
deposi ed by ha ching, had equiaxed g ains ha did no change
hei size be ween laye s, he e o e i was concluded ha his sam-
ple had a uni o m mic os uc u e along i s heigh . The s aigh wall
geome y howe e , had a dend i ic mic os uc u e, wi h columna
g ains in he in e laye zone, i espec i ely o he leng h and he
o ch mo emen (ha ching o ci cling). As explained be o e, he
columna na u e o he mic os uc u e was enhanced in sho e
s aigh WAAM wall ( e ical). Resul s ha e shown ha he solu-
ion and aging hea ea men did no change he mic os uc u e,
in e ms o nei he g ain size no mo phology. In his sense, colum-
na and e ically elonga ed g ains ob ained in s aigh wall sam-
ples kep hei shape a e ull aging ea men . I mus be
highligh ed ha seg ega ions esul ing om dend i ic solidi ica-
ion s uc u es we e homogenized a e he mal ea men and
he g ains looked cleane in compa ison wi h he as-buil s a e
(Fig. 12).
As Aya kwa e al. [27] epo ed, columna g ains esul s om a
unidi ec ional o ien ed hea lux du ing hea ans e om a mel
in o a coole solid. Since s aigh walls shown columna g ains p o-
nounced e ical he mal g adien s in he pa will explain he
p e e en ial g ow h o g ains along his di ec ion. Con e sely, he
coa se equiaxed g ain s uc u e in ec angula geome y would
be he esul o low empe a u e g adien and slowe cooling a e
due o a highe hea accumula ion. I is mo e han clea looking a
Table 3 ha samples wi h hese equiaxed g ains shown mo e bal-
anced mechanical p ope ies and educed aniso opy a e p ope
aging he mal ea men .
In e ms o he mal ea men , he e ec o aging empe a u e
and ime is e iden om he da a shown in Table 3. F om his
s udy, i is concluded ha longe aging imes esul in an inc ease
in he mechanical p ope ies as compa ed o wo k pe o med on
single bead wid h walls by Gu e al. [7].
These au ho s [29 7], used a sho a i icial aging ea men
keeping he samples a 175 °C o 3 h a e solu ion ea men a
535 °C du ing 90 min. As o Aya kwa e al. [29] used o he same
2319 alloy, an al e na i e he mal ea men consis ing o 12 h
aging ime a 171 °C wi h s epped hea ing. In his case he solu ion
empe a u e and ime we e simila . In he cu en wo k, compa a-
ble sho and long hea ea men s a 175 °C and 190 °C, being he
la es he ecommended aging empe a u e by ASM Handbook
[30], we e used. The compa ison, has enabled o conclude on he
e ec o he he mal ea men on 2319 WAAM samples manu ac-
u ed wi h he same welding pa ame e s. F om hese esul s, i has
been obse ed, ha long aging imes and 190 °C empe a u e ha e
a bene icial e ec on aniso opy educ ion, inc easing bo h
s eng h and duc ili y.
Mic oha dness and ensile es esul s demons a ed a di ec
ela ionship be ween ha dness and elonga ion capabili y in he
e ical di ec ion agains aging ime and empe a u e. Sho p e-
cipi a ion imes lead o high ha dness and low o null elonga ion.
Fo s aigh wall geome y, hea ea men u he a ec ed he
mechanical p ope ies in compa ison wi h ec angula geome y.
Sho p ecipi a ion imes du ing he aging phase led o p ema u e
ac u e du ing he ensile es , wi hou eaching plas ic de o ma-
ion o yield s ess, while ec angula geome y shown be e
mechanical p ope ies. In his case, he aniso opy a e 175 °C
aging empe a u e was g ea e han he one ob ained wi h
190 °C(Table 4). On he o he hand, o s aigh wall geome y
Fig. 12. Mic os uc u e be o e and a e hea ea men .
M. A ana, E. Uka , I. Rod iguez e al. Ma e ials & Design 221 (2022) 110974
9
