

Ci a ion: Rajesh, P.V.; Gup a, K.K.;
ˇ
Cep, R.; Ramachand an, M.; Kouˇ il,
K.; Kali a, K. Op imizing F ic ion S i
Welding o Dissimila G ades o
Aluminum Alloy Using WASPAS.
Ma e ials 2022,15, 1715. h ps://
doi.o g/10.3390/ma15051715
Academic Edi o s: Vic o Songmene,
Fawzy Hosny Samuel and
Tomasz T zepieci´nski
Recei ed: 7 Janua y 2022
Accep ed: 23 Feb ua y 2022
Published: 24 Feb ua y 2022
Publishe ’s No e: MDPI s ays neu al
wi h ega d o ju isdic ional claims in
published maps and ins i u ional a il-
ia ions.
Copy igh : © 2022 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
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dis ibu ed unde he e ms and
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A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
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ma e ials
A icle
Op imizing F ic ion S i Welding o Dissimila G ades o
Aluminum Alloy Using WASPAS
Pinna asal Venuk ishnan Rajesh 1, K ishna Kuma Gup a 2, Robe ˇ
Cep 3,* , Manickam Ramachand an 4,
Ka el Kouˇ il 5and Kanak Kali a 6,*
1Depa men o Mechanical Enginee ing, Sa ana han College o Enginee ing, T ichy 620012, India;
[email p o ec ed]
2Depa men o Mechanical Enginee ing, Malwa Ins i u e o Science and Technology, Indo e 453111, India;
[email p o ec ed]
3Depa men o Machining, Assembly and Enginee ing Me ology, Facul y o Mechanical Enginee ing,
VSB-Technical Uni e si y o Os a a, 708 00 Os a a, Czech Republic
4Da a Analy ics Lab, REST Labs, Ka e ipa inam 635112, India; [email p o ec ed]
5Ins i u e o Manu ac u ing Technology, Facul y o Mechanical Enginee ing, B no Uni e si y o Technology,
Technicka 2896/2, 616 69 B no, Czech Republic; ka el.kou il@ u b .cz
6Depa men o Mechanical Enginee ing, Vel Tech Ranga ajan D . Sagun hala R&D Ins i u e o Science and
Technology, A adi 600062, India
*Co espondence: [email p o ec ed] (R. ˇ
C.); [email p o ec ed] (K.K.)
Abs ac :
Aluminum is a widely popula ma e ial due o i s low cos , low weigh , good o mabili y
and capabili y o be machined easily. When a non-me al such as ce amic is added o aluminum
alloy, i o ms a composi e. Me al Ma ix Composi es (MMCs) a e eme ging as al e na i es o
con en ional me als due o hei abili y o wi hs and hea y load, excellen esis ance o co osion and
wea , and compa a i ely high ha dness and oughness. Aluminum Ma ix Composi es (AMCs), he
mos popula ca ego y in MMCs, ha e innume able applica ions in a ious ields such as scien i ic
esea ch, s uc u al, au omobile, ma ine, ae ospace, domes ic and cons uc ion. Thei a ac i e
p ope ies such as high s eng h- o-weigh a io, high ha dness, high impac s eng h and supe io
ibological beha io enable hem o be used in au omobile componen s, a ia ion s uc u es and pa s
o ships. Thus, in his esea ch wo k an a emp has been made o ab ica e Aluminum Alloys and
Aluminum Ma ix Composi es (AMCs) using he popula syn hesis echnique called s i cas ing and
join hem by ic ion s i welding (FSW). Dissimila g ades o aluminum alloy, i.e., Al 6061 and Al
1100, a e used o he expe imen al wo k. Alumina and Silicon Ca bide a e used as ein o cemen
wi h he aluminum ma ix. Mechanical and co osion p ope ies a e expe imen ally e alua ed. The
FSW p ocess is analyzed by expe imen ally compa ing he welded alloys and welded composi es.
Finally, he bes sui able FSW combina ion is selec ed wi h he help o a Mul i-A ibu e Decision
Making (MADM)-based nume ical op imiza ion echnique called Weigh ed Agg ega ed Sum P oduc
Assessmen (WASPAS).
Keywo ds:
aluminum; alloys; composi es; s i cas ing; ic ion s i welding; pa ame e s; p ope ies;
mul i-a ibu e decision making; op imiza ion
1. In oduc ion
An alloy is a mix u e o wo o mo e me als a speci ic p opo ions. Gene ally, all
me als exis in he o m o alloys. Aluminum, he mos abundan me al in he Ea h’s c us ,
is ex ac ed om bauxi e o e and pu i ied as an alloy. Aluminum alloys con ain aluminum
as he majo cons i uen (>90%), wi h mino aces o o he me als. Based on he chemical
composi ion (i.e., p edominance o one o wo mino cons i uen s o he han aluminum),
aluminum alloys a e ca ego ized in o di e en g ades [
1
]. Each g ade inds i s usage in a
pa icula applica ion. These alloys can be made in o blooms, bille s o ods o comme cial
pu poses, ei he by means o ex usion o cas ing.
Ma e ials 2022,15, 1715. h ps://doi.o g/10.3390/ma15051715 h ps://www.mdpi.com/jou nal/ma e ials
Ma e ials 2022,15, 1715 2 o 12
Aluminum Ma ix Composi es (AMC) a e o med when one o mo e non-me al (mos
p e e ably ce amics) is ein o ced in o he aluminum alloy, so ha he esul an ma e ial
will be ha ing imp o ed physical, mechanical and ibological p ope ies, compa ed o
indi idual alloy [
2
]. E en hough AMCs a e ab ica ed by nume ous p ocessing echniques,
cas ing emains he mos popula and inexpensi e me hod.
Weldabili y is an impo an p ope y ha enables alloys o MMCs o be welded in o
di e en shapes and dimensions. The excellen weldabili y o aluminum makes i one o
he mos sough -a e me al alloys o s uc u al applica ions [
3
]. Welding is a me al joining
p ocess in which wo me al pieces o egula c oss-sec ion a e joined oge he wi h he
applica ion o hea . F ic ion S i Welding is one o he ecen echniques o join aluminum
alloys and hei associa ed composi es [4,5].
Mul i-C i e ia Decision Making (MCDM) is a quan i a i e analysis-based op imiza ion
me hodology in which he bes possible solu ion is selec ed om a se o al e na i es based
on anking, when con as ing c i e ia a e aken in o accoun [
6
]. I is b oadly classi ied in o
wo dis inc i e ca ego ies: one is Mul i-A ibu e Decision Making (MADM), a model o
sol e p oblems wi h a disc e e da a se , and he o he is Mul i-Objec i e Decision Making
(MODM), a model o sol e p oblems wi h a con inuous o analog da a se [7,8].
In his pape , MADM is used o iden i y he op imal combina ion o he FSW p ocess as
he esul s ob ained om a ious es s a e non-con inuous/disc e e in na u e. By e iewing
a ious li e a u es ela ed o he FSW o aluminum alloys and AMCs, an in e ence has
been ob ained ha FSW is done only in alloy–alloy combina ions (simila o dissimila
g ades) and composi e–composi e combina ions, wi h he same ce amic used in bo h pla es.
To add ess his gap, an a emp has been made o ab ica e and analyze FSW in alloy–
composi e combina ions and composi e–composi e combina ions, wi h di e en ce amics
in bo h he side pla es. The dissimila aluminum alloys and composi es a e welded by
FSW and expe imen ally cha ac e ized o ind he ul ima e ensile s eng h and ha dness.
The co osion esis ances o he welds a e also expe imen ally analyzed. The es o he
pape is a anged as ollows: Sec ion 2desc ibes he expe imen al me hodology used o
ab ica e he composi es and hei p ocessing. Sec ion 3de ails he expe imen al indings in
a sys ema ic way. The indings o bo h he mechanical and co osion es s a e de ailed he e
and ca e ully analyzed. Sec ion 4in oduces and sol es he mul i-c i e ia decision-making
p oblem in a s ep-by-s ep way. Finally, succinc conclusions based on he expe imen al and
MCDM simula ions a e d awn in Sec ion 5.
2. Me hodology
2.1. Selec ion o Ma e ials
Fo ab ica ing AMCs, he p elimina y equi emen is o selec ma e ials o ma ix as
well as ein o cemen . This sec ion o he pape deals wi h he selec ion and p ocu emen
o aw ma e ials o cas ing.
(a)
Ma ices
Ma ix is he encompassing pa ha co e s he composi e s uc u e. In an AMC, i
is necessa ily an aluminum alloy wi h maximum p opo ion. Two dis inc i e g ades o
aluminum alloy Al 6061 and Al 1100 a e selec ed as ma ices.
Al 6061 is he mos common and abundan ly used p ecipi a ion-s eng hened w ough
aluminum alloy wi h signi ican pe cen ages o silicon and magnesium. I has good
wo kabili y, supe io su ace inish and excellen co osion esis ance [
1
]. The p opo ion o
me als p esen in Al 6061 alloy is gi en below in Table 1.
Table 1. Elemen al analysis o Al 6061.
Cons i uen s Al Mn Fe Cu Mg Si C
Pe cen age 97.74 0.11 0.13 0.39 0.97 0.62 0.08
Ma e ials 2022,15, 1715 3 o 12
Al 1100 is he pu es alloy in he w ough aluminum amily o 1xxx se ies. This
mechanically s onges alloy has good he mal p ope ies and be e wo kabili y. The
chemical composi ion o Al 1100 is gi en below in Table 2.
Table 2. Elemen al analysis o Al 1100.
Cons i uen s Al Mn Fe Cu Mg Si C
Pe cen age 99.00 0.05 0.40 0.05 0.04 0.40 0.01
(b)
Rein o cemen s
Rein o cemen is he ma e ial p esen a minimum p opo ion ha is inse ed in he
me allic ma ix as a ibe , powde o whiske . I p o ides binding s eng h o he composi e
he ein. Two popula ce amics, Alumina (Al
2
O
3
) and Silicon Ca bide (SiC), a e selec ed as
ein o cemen s in his esea ch wo k. These ce amics a e syn he ic in na u e, wi h good
ab asi e p ope ies and hea -wi hs anding capaci y. They a e used o inc ease he ha dness
and wea esis ance o he composi e [
2
,
9
]. The gene al p ope ies o bo h he ce amics a e
gi en in Table 3.
Table 3. Gene al p ope ies o he ce amics.
P ope ies Uni s Aluminum
Oxide (Al2O3)
Silicon Ca bide
(SiC)
Densi y g/cm33.98 3.1
Mel ing poin ◦C 2300 2730
Vicke s ha dness - 1560 4483
F ac u e oughness MPa√m 4.9 4.6
Elas ic modulus GPa 300 410
Tensile s eng h MPa 210 137.9
The mal conduc i i y W/Mk 21 120
Coe icien o he mal expansion m/◦C9.0 ×10−64.0 ×10−6
2.2. Fab ica ion Me hod
The me hod used o ab ica e composi e specimens and some imes alloys o unusual
me al-mix a io is s i cas ing, al e na i ely known as g a i y die cas ing [
10
]. In his
me hod, he me al alloy is mel ed and cas ed in o equi ed shape and size. Ini ially, he
me al alloys o be mel ed a e pu in o g aphi e c ucible and kep inside a coal-igni ed
u nace. The combus ion o he u nace is con olled using a mechanized blowe . When he
aluminum alloys each liquidus s age o semi-solid s a e, he p ehea ed ce amic powde s
a e pou ed inside he mol en me al and s i ed ho oughly (ei he manually o wi h he
help o p opelle ) o ensu e uni o m dis ibu ion o ein o ced pa icles inside me allic
ma ix. Insu icien s i ing may esul in he s agna ion o ce amic powde s as esidue a
he bo om o c ucible. This mix u e is hen pou ed in o mould ca i y o desi able shape
and dimension [
1
]. In p esen esea ch wo k, i is a mild s eel die. A e solidi ica ion,
he cas ed composi e is emo ed om he die and quenched in no mal ai . Weigh o
me al alloy equi ed o cas ing 1 composi e pla e measu ing 150
×
150
×
5 mm
3
as pe
mass-based a io is as ollows:
Densi y o Al 6061 = Al 1100 ≈2.7 g/cm3;
Requi ed Volume o he composi e = 15 ×15 ×0.5 = 112.5 cm3;
Densi y = mass/ olume;
Requi ed mass o he me al alloy = densi y × olume = 2.7 ×112.5 = 303.75 g;
Cas ing allowance (sh inkage allowance) = 15% o mass;
Hence, inal equi ed mass o me al = 303.75 + (0.15 ×303.75) = 349.31 g ≈350 g.
In mass-based a io, he pe cen age o me al alloy is kep cons an as 100%. Inc ease
in me al alloy % will inc ease he dimension o size o he composi e. Fo equi ed shape
Ma e ials 2022,15, 1715 4 o 12
o be ob ained, p opo ion o me al alloy should no be educed as in olume-based a io.
Reduc ion in me al alloy % will esul in incomple e shape o cas ing. Addi ion o ein-
o cemen powde s will help o inc ease weigh o he composi e as bo h he ce amics a e
dense han he wo di e en g ades o aluminum alloy. The alloys and composi es’ combi-
na ion ab ica ed using s i cas ing is men ioned below. Th ee specimens a e ab ica ed o
each composi ion.
1. 100% Al 6061 (350 g);
2. 100% Al 1100 (350 g);
3. 100% Al 6061 (350 g) + 5% Al2O3(17.5 g);
4. 100% Al 1100 (350 g) + 5% Al2O3(17.5 g);
5. 100% Al 6061 (350 g) + 5% SiC (17.5 g);
6. 100% Al 1100 (350 g) + 5% SiC (17.5 g).
2.3. P ocessing Technique
This sec ion deals wi h ic ion s i welding o composi e pla es. FSW is he p edom-
inan ly used echnique o join wo pla es, made up o aluminum alloys o aluminum
composi es [
11
]. The composi e o alloy pla es o be welded oge he a e placed in close
p oximi y, so ha hei longi udinal edges ouch each o he and a e hinged. The en i e
wo k-holding se up is placed in e ical milling machine (P ecicu , Noida, India). The ool
holde is comp ised o a cylind ical ool made o s ainless s eel o diame e 15 mm wi h
nose ip adius and heigh measu ing 3 mm and 4 mm, espec i ely. When he o a ing ool
comes in o con ac wi h he s a iona y pla es, a welding ac ion is c ea ed h oughou he
mee ing line (junc ion) o he wo pla es, due o hea gene a ed by ic ion he eby joining
hem [
5
,
12
]. The p ocess pa ame e s used in FSW a e p esen ed in Table 4. Figu e 1shows
a se o pla es joined by FSW.
Table 4. P ocess pa ame e s in F ic ion S i Welding.
Pa ame e s Values Uni s
Tool o a ional speed 1000 pm
T a e se eed 50 mm/min
Di ec ion o ool o a ion Clock-wise -
Tool pin shape Cylind ical -
Tool ma e ial S ainless s eel -
Tool pin nose adius 3 mm
Ma e ials2022,15,17154o 13


Requi edmasso  heme alalloy=densi y× olume=2.7×112.5=303.75g;
Cas ingallowance(sh inkageallowance)=15%o mass;
Hence, inal equi edmasso me al=303.75+(0.15×303.75)=349.31g≈350g.
Inmass‐based a io, hepe cen ageo me alalloyiskep cons an as100%.Inc ease
inme alalloy%willinc ease hedimensiono sizeo  hecomposi e.Fo  equi edshape
obeob ained,p opo iono me alalloyshouldno be educedasin olume‐based a io.
Reduc ioninme alalloy%will esul inincomple eshapeo cas ing.Addi iono  ein‐
o cemen powde swillhelp oinc easeweigh o  hecomposi easbo h hece amicsa e
dense  han he wodi e en g adeso aluminumalloy.Thealloysandcomposi es’com‐
bina ion ab ica edusings i cas ingismen ionedbelow.Th eespecimensa e ab ica ed
o eachcomposi ion.
1. 100%Al6061(350g);
2. 100%Al1100(350g);
3. 100%Al6061(350g)+5%Al2O3(17.5g);
4. 100%Al1100(350g)+5%Al2O3(17.5g);
5. 100%Al6061(350g)+5%SiC(17.5g);
6. 100%Al1100(350g)+5%SiC(17.5g).
2.3.P ocessingTechnique
Thissec iondealswi h ic ions i weldingo composi epla es.FSWis hep edom‐
inan lyused echnique ojoin wopla es,madeupo aluminumalloyso aluminumcom‐
posi es[11].Thecomposi eo alloypla es obewelded oge he a eplacedinclosep ox‐
imi y,so ha  hei longi udinaledges oucheacho he anda ehinged.Theen i ewo k‐
holdingse upisplacedin e icalmillingmachine(P ecicu ,Noida,India).The ool
holde iscomp isedo acylind ical oolmadeo s ainlesss eelo diame e 15mmwi h
nose ip adiusandheigh measu ing3mmand4mm, espec i ely.When he o a ing
oolcomesin ocon ac wi h hes a iona ypla es,aweldingac ionisc ea ed h oughou 
hemee ingline(junc ion)o  he wopla es,due ohea gene a edby ic ion he eby
joining hem[5,12].Thep ocesspa ame e susedinFSWa ep esen edinTable4.Figu e
1showsase o pla esjoinedbyFSW.
Table4.P ocesspa ame e sinF ic ionS i Welding.
Pa ame e sValuesUni s
Tool o a ionalspeed1000 pm
T a e se eed50mm/min
Di ec iono  ool o a ionClock‐wise‐
ToolpinshapeCylind ical‐
Toolma e ialS ainlesss eel‐
Toolpinnose adius3mm

Figu e1.F ic ionS i Weldingspecimens.
Figu e 1. F ic ion S i Welding specimens.
The 9 di e en specimen combina ions c ea ed by FSW a e ep esen ed as ollows:
1. Al 6061 wi h Al 1100;
2. Al 6061 wi h Al 1100/5% Al2O3;
3. Al 6061 wi h Al 1100/5% SiC;
Ma e ials 2022,15, 1715 5 o 12
4. Al 1100 wi h Al 6061/5% Al2O3;
5. Al 1100 wi h Al 6061/5% SiC;
6. Al 6061/5% Al2O3wi h Al 1100/5% Al2O3;
7. Al 6061/5% Al2O3wi h Al 1100/5% SiC;
8. Al 6061/5% SiC wi h Al 1100/5% Al2O3;
9. Al 6061/5% SiC wi h Al 1100/5% SiC.
I should be no ed ha he FSW p ocess pa ame e s ha e signi ican in luence on
he mechanical and mo phological p ope ies o he weld. Thus, op imizing hem is also
a ealis ic goal. Howe e , op imiza ion o FSW p ocess pa ame e s o each o he nine
ma e ial combina ions lis ed abo e would equi e exhaus i e expe imen a ion. E en by
using design o expe imen a ion me hods such as Box–Behnken, cen al composi e design,
e c., he numbe o expe imen s needed o all he ma e ial combina ions o asce ain he
op imal p ocess pa ame e s will be e y la ge. Thus, in his s udy he p ocess pa ame e s
in Table 4a e decided h ough an ex ensi e li e a u e e iew.
3. Expe imen al Resul s
E alua ion o FSW p ocess is done h ough conduc ing a ious es s ha depic
di e en ma e ial beha io . In his esea ch wo k, app op ia e es s a e conduc ed o
analyze he mechanical p ope ies such as ensile s eng h and ha dness, as well as co osion
esis ance beha io o he di e en weld combina ions ha consis o alloys and composi es.
Values ob ained om mechanical es s and co osion es s a e also compa ed among he
weld specimens o asce ain he co esponding endency (as o which combina ion gi es
bes esul s).
3.1. Mechanical Tes s
The es s co e ed unde his sec ion a e pe o med o iden i y he ul ima e ensile
s eng h (UTS) and B inell Ha dness Numbe (BHN) o he weld specimens. The es
samples a e p epa ed wi h dimensions as pe ASTM S anda d Tes Me hods.
3.1.1. Tensile Tes
This es is done o measu e he duc ili y o he ma e ial. Duc ili y is he endency,
which makes he ma e ial mo e lexible so ha i can be d awn in o leng hy and hin
wi e [
1
]. Duc ile ma e ials such as aluminum a e mo e elas ic in na u e. Tensile es is
conduc ed in ension chambe (Blue S a , Mumbai, India) o uni e sal es ing machine
(UTM). The FSW specimens o di e en combina ions a e cu and p epa ed as shown in
Figu e 2. These es samples a e ixed be ween a ixed jaw and mo ing jaw o UTM one
a e he o he . When he mo able jaw s a s o mo e e ically due o hyd aulic powe ,
pulling o ce is applied o he sample and s a s o elonga e. As he sample en e s he plas ic
egion a e lea ing elas ic egion, i abso bs maximum s ess be o e b eaking. Maximum
change in leng h (inc ease in leng h and educ ion in c oss-sec ional a ea) occu s du ing
he exe ion o maximum load o ul ima e ensile s ess. Table 5 ep esen s he esul s o
ensile es conduc ed on 9 FSW combina ion samples.
The esul s indica e ha he FSW specimen 4 in which Al 1100 alloy is welded wi h
Al 6061/5% Al
2
O
3
composi e gi es he highes UTS. This indica es pe ec bond be ween
wo pla es a weldmen egion. The FSW combina ion o Al 6061 alloy wi h Al 1100 alloy
gi es he second highes alue compa ed o o he combina ions, as alloy exhibi s mo e
duc ili y han composi e. The welding combina ion in which Al 6061/5% SiC is joined wi h
Al 1100/5% Al
2
O
3
has lowes ensile s eng h as he p esence o bo h ce amics induces
b i leness and makes he FSW bond weak. The FSW combina ions in ol ing SiC p oduce
educed ensile s eng h as SiC is ha de han Al2O3.

Ma e ials 2022,15, 1715 6 o 12
Ma e ials2022,15,17156o 13



Figu e2.Tensile es samplesaspe ASTMS anda ds.
Table5.Tensile es  esul s.
Specimen
No.
MaximumLoadGi en o
Specimen,Pmax
O iginalC oss‐Sec ionA eaa 
NeckRegion(bx ),Ao
UTS,T=
Pmax/Ao
Elonga ion=Changein
Leng h/O iginalLeng h
Nmm2Mpa%
1479039.92119.996.82
2408040.24101.395.84
3332039.9783.066.06
4545040.12135.844.78
5310039.8877.735.24
6426040.17106.056.32
7333040.0883.086.48
8277040.0269.224.56
9392040.2297.465.68
The esul sindica e ha  heFSWspecimen4inwhichAl1100alloyisweldedwi h
Al6061/5%Al2O3composi egi es hehighes UTS.Thisindica espe ec bondbe ween
wopla esa weldmen  egion.TheFSWcombina iono Al6061alloywi hAl1100alloy
gi es hesecondhighes  aluecompa ed oo he combina ions,asalloyexhibi smo e
duc ili y hancomposi e.Theweldingcombina ioninwhichAl6061/5%SiCisjoinedwi h
Al1100/5%Al2O3haslowes  ensiles eng has hep esenceo bo hce amicsinduces
b i lenessandmakes heFSWbondweak.TheFSWcombina ionsin ol ingSiCp oduce
educed ensiles eng hasSiCisha de  hanAl2O3.
3.1.2.Ha dnessTes 
This es isdone omeasu e heha dnesso  hespecimensbycalcula ingB inell
Ha dnessNumbe (BHN).Ha dnessis heex en  owhichama e ialcanwi hs and
ab adingo inden ingload.Thespecimensa eplaced la in heha dness es e so ha a
poin loado 250kg isappliedo e  heweldmen su acebyas eelballinden e o di‐
ame e 5mmandheldcons an ly o 10s.Thediame e o  heimp essionc ea edbyin‐
den e isin e selyp opo ional o heha dness[9].TheBHNiscalcula ed om he ol‐
lowingEqua ion(1).TheB inellha dness alueso  he9FSWspecimensa e abula ed
belowinTable6.
BHN  2𝑃
𝜋𝐷𝐷
√
𝐷𝑑 (1)
whe e
P=cons an loadappliedonweldmen (250kg );
Figu e 2. Tensile es samples as pe ASTM S anda ds.
Table 5. Tensile es esul s.
Specimen
No.
Maximum Load Gi en o
Specimen, Pmax
O iginal
C oss-Sec ion A ea a
Neck Region (bx ), Ao
UTS, T = Pmax/AoElonga ion = Change in
Leng h/O iginal Leng h
Nmm2Mpa %
1 4790 39.92 119.99 6.82
2 4080 40.24 101.39 5.84
3 3320 39.97 83.06 6.06
4 5450 40.12 135.84 4.78
5 3100 39.88 77.73 5.24
6 4260 40.17 106.05 6.32
7 3330 40.08 83.08 6.48
8 2770 40.02 69.22 4.56
9 3920 40.22 97.46 5.68
3.1.2. Ha dness Tes
This es is done o measu e he ha dness o he specimens by calcula ing B inell
Ha dness Numbe (BHN). Ha dness is he ex en o which a ma e ial can wi hs and
ab ading o inden ing load. The specimens a e placed la in he ha dness es e so ha
a poin load o 250 kg is applied o e he weldmen su ace by a s eel ball inden e o
diame e 5 mm and held cons an ly o 10 s. The diame e o he imp ession c ea ed by
inden e is in e sely p opo ional o he ha dness [
9
]. The BHN is calcula ed om he
ollowing Equa ion (1). The B inell ha dness alues o he 9 FSW specimens a e abula ed
below in Table 6.
BHN =2P
πDhD−√D2−d2i(1)
whe e
P= cons an load applied on weldmen (250 kg );
D= diame e o s eel ball inden e (5 mm);
d= diame e o he imp ession in mm.
The esul s indica e ha ic ion-s i -welded AMCs a e ha ing highe ha dness han
ic ion-s i -welded aluminum alloy. The addi ion o SiC plays a signi ican ole as i p o-
ides mo e ha dness han Al
2
O
3
. The alloy weld combina ion has he minimum ha dness,
whe eas he SiC- ein o ced composi e weld combina ion shows maximum ha dness. The
alloy–composi e weld specimens a e ha de han alloy–alloy weld specimens bu ha e
lowe ha dness alue han composi e–composi e weld specimens.
Ma e ials 2022,15, 1715 7 o 12
Table 6. Ha dness es esul s.
Specimen No. Diame e o he Imp ession, d B inell Ha dness
Mm BHN
1 3.80 42.43
2 3.67 45.61
3 3.50 50.34
4 3.57 48.30
5 3.47 51.23
6 3.53 49.44
7 3.40 53.43
8 3.43 52.47
9 3.33 55.77
3.2. Co osion Tes
Co osion is a bulk ma e ial emo al p ocess. I is de ined as he emo al o ma e ial
h oughou he specimen, due o some chemical ac ion o eac ion. Co osion es is
done o iden i y he specimen, which is ha ing bes co osion esis ance among di e en
combina ions. Imme sion co osion es is he mos popula and widely used co osion
es , especially o aluminum alloys and AMCs [
9
]. In his es , samples a e cu om he
nine weld combina ions such ha he weldmen egion lies in be ween he sample and
is p epa ed as pe ASTM S anda d G31. These samples a e imme sed sepa a ely in acid
and alkaline (base) solu ions o known concen a ion (1 no mali y) o a speci ic pe iod o
ime (24 h). Then, hey a e aken ou and he mass loss due o co osion is ound ou om
he di e ence be ween he ini ial weigh o he sample be o e dipping i in o co oding
medium and he inal weigh o he sample a e emo ing i om he co oding medium.
Finally, he co osion a e is calcula ed om he o mula men ioned in Equa ion (2):
CR =87.6W
ρAT (2)
whe e
CR = co osion a e exp essed in millime e pe yea (mm/y);
W= mass loss due o co osion in mg;
ρ= densi y o he sample in g/cm3;
A= c oss-sec ional a ea o he sample in cm2;
T= ime o exposu e in hou s.
Then, he uni o co osion a e is con e ed in o mils pe yea (mpy) using he below
men ioned Equa ion (3).
1 mpy =0.0254 mm/y (3)
Lowe he co osion a e, be e he co osion esis ing capaci y o he weld specimen.
Table 7 ep esen s he co osion a e o he specimens imme sed in acidic and basic media.
The in e ences ob ained om he abo e es esul s clea ly show ha he alloy–
composi e and composi e–composi e weld combina ions o e mo e co osion esis ance
han alloy–alloy weld combina ion. The composi e–composi e weld combina ions a e e en
be e han alloy–composi e combina ion. The ein o cemen o alumina plays a c ucial ole
in educing he co osion a e in weld specimens. The specimens con aining alumina ha e
be e co osion esis ance han he specimens wi h Silicon Ca bide.
Ma e ials 2022,15, 1715 8 o 12
Table 7. Imme sion co osion es esul s.
Specimen No.
Acidic Co osion Ra e, CRABasic Co osion Ra e, CRB
In Acid Solu ion (HCl) In Base Solu ion (NaOH)
mm/y mpy mm/y mpy
1 28.01 0.71 52.29 1.33
2 18.12 0.46 28.17 0.72
3 21.45 0.54 33.76 0.86
4 17.54 0.45 26.93 0.68
5 19.72 0.50 29.61 0.75
6 11.28 0.29 17.15 0.44
7 13.38 0.34 19.46 0.49
8 14.18 0.36 24.07 0.61
9 16.75 0.43 25.86 0.66
4. Selec ion o Op imal FSW Combina ion Using Weigh ed Agg ega ed Sum P oduc
Assessmen (WASPAS)
The weigh ed agg ega ed sum p oduc assessmen (WASPAS) is one o he mos
ecen MADM-inspi ed op imiza ion app oaches, which uses a unique combina ion o
weigh ed sum model (WSM) and weigh ed p oduc model (WPM) o induce highe anking
accu acy [
13
]. This me hod was i s p oposed by Za adskas e al. in 2012 [
14
]. In his
me hod, he ela i e impo ance o each a ibu e/c i e ion is de e mined ini ially ollowed
by he e alua ion and p io i iza ion o he gi en se o al e na i es.
The o mulae and he s ep-by-s ep p ocedu e o op imizing he abo e de ailed FSW
p ocess is gi en below.
(a)
Decision Ma ix Table
The op imiza ion p ocess s a s wi h he cons uc ion o decision ma ix able. He e,
‘m’ e e s o he al e na i es (i.e., nine FSW combina ions) and ‘n’ deno es a ibu es o
c i e ia (i.e., ou ou pu p ope ies). Rows a e deno ed by ‘i’, and columns a e deno ed
by ‘j’. X
ij
e e s o he j h a ibu e alue o i h al e na i e [
15
]. The decision ma ix is
ep esen ed as Equa ion (4).
D=


X11 ··· X1n
.
.
.....
.
.
Xm1··· Xmn


(4)
Table 8indica es he decision ma ix able c ea ed o he abo e-explained
esea ch wo k.
Table 8. Decision ma ix.
Specimen No. A ibu es
UTS (MPa) BHN CRA(mpy) CRB(mpy)
1 119.99 42.43 0.71 1.33
2 101.39 45.61 0.46 0.72
3 83.06 50.34 0.54 0.86
4 135.84 48.3 0.45 0.68
5 77.73 51.23 0.5 0.75
6 106.05 49.44 0.29 0.44
7 83.08 53.43 0.34 0.49
8 69.22 52.47 0.36 0.61
9 97.46 55.77 0.43 0.66
Ma e ials 2022,15, 1715 9 o 12
(b)
Linea No maliza ion o Decision Ma ix
No maliza ion o decision ma ix able elemen s is done o con e hose alues in o
same uni ac o s [
15
]. The o mulae o no malizing elemen s in bene icia y and non-
bene icia y a ibu es a e gi en as Equa ions (5) and (6).
Fo bene icia y a ibu e,
ij =xij
max
ixij
(5)
Fo non-bene icia y a ibu e,
ij =
min
ixij
xij
(6)
Table 9indica es no malized decision ma ix.
Table 9. No malized decision ma ix.
Specimen No. A ibu es
UTS (MPa) BHN CRA(mpy) CRB(mpy)
1 0.88 0.76 0.41 0.33
2 0.75 0.82 0.63 0.61
3 0.61 0.90 0.54 0.51
4 1.00 0.87 0.64 0.65
5 0.57 0.92 0.58 0.59
6 0.78 0.89 1.00 1.00
7 0.61 0.96 0.85 0.90
8 0.51 0.94 0.81 0.72
9 0.72 1.00 0.67 0.67
Table 10 indica es he a ibu es ha all unde bene icia y and non-bene icia y ca e-
go y, wi h he co esponding weigh ac o s based on hei ela i e impo ance.
Table 10. A ibu es and hei weigh age.
Sl. No. C i e ia Ca ego y Objec i e Weigh age, wj
1 UTS Bene icia y (La ge - he-be e ) Maximiza ion 0.30
2 BHN Bene icia y (La ge - he-be e ) Maximiza ion 0.30
3 CRACos (Smalle - he-be e ) Minimiza ion 0.20
4 CRBCos (Smalle - he-be e ) Minimiza ion 0.20
(c)
C ea ion o join c i e ion o op imali y
Fi s c i e ion o op imali y deals wi h weigh ed sum model (WSM)-based calcula ion
o ela i e impo ance o i h al e na i e using he ollowing Equa ion (7),
Qi(1)=∑n
j=1 ij ∗wj(7)
Figu e 3shows he weigh ed no malized decision ma ix along wi h he WSM p e -
e en ial sco e. Since he UTS and BHN a e maximiza ion ype whe eas he CR
A
and CR
B
a e minimiza ion ype, he pa allel plo p o ides a good isualiza ion ool o inspec he
e ec o each o he ou esponses on he WSM p e e en ial sco e. I should be no ed ha
due o Equa ions (5) and (6), he minimiza ion ype esponses a e on an in e ed scale
wi h e e ence o he maximiza ion ype esponses. I is obse ed om Figu e 3 ha he
combina ion o a mode a e le el o UTS and BHN and leas alue o CR
A
and CR
B
is
de e mined as he bes solu ion as pe WSM.