Investigation of microstructure and mechanical properties of SLM-fabricated AlSi10Mg alloy post-processed using equal channel angular pressing (ECAP)

Ci a ion: Snopi´nski, P.; Appiah, A.N.S.; Hilše , O.; Ko oul, M. In es iga ion o Mic os uc u e and Mechanical P ope ies o SLM-Fab ica ed AlSi10Mg Alloy Pos -P ocessed Using Equal Channel Angula P essing (ECAP). Ma e ials 2022,15, 7940. h ps://doi.o g/ 10.3390/ma15227940 Academic Edi o s: Joan-Josep Suñol and Lluïsa Escoda Recei ed: 24 Oc obe 2022 Accep ed: 8 No embe 2022 Published: 10 No embe 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. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). ma e ials A icle In es iga ion o Mic os uc u e and Mechanical P ope ies o SLM-Fab ica ed AlSi10Mg Alloy Pos -P ocessed Using Equal Channel Angula P essing (ECAP) P zemysław Snopi´nski 1,* , Augus ine Nana Sekyi Appiah 2, Ond ej Hilše 3and Michal Ko oul 4 1Depa men o Enginee ing Ma e ials and Bioma e ials, Silesian Uni e si y o Technology, 18A Kona skiego S ee , 44-100 Gliwice, Poland 2Ma e ials Resea ch Labo a o y, Silesian Uni e si y o Technology, 18A Kona skiego S ee , 44-100 Gliwice, Poland 3 Facul y o Mechanical Enginee ing, VSB-TU Os a a, 17. lis opadu 2172/15, 708 00 Os a a, Czech Republic 4Ins i u e o Solid Mechanics, Mecha onics and Biomechanics, B no Uni e si y o Technology, Technická2896/2, 616 69 B no, Czech Republic *Co espondence: p zemyslaw[email p o ec ed] Abs ac : Wi h he aim o imp o ing he excellen mechanical p ope ies o he SLM-p oduced AlSi10Mg alloy, his esea ch ocuses on pos -p ocessing using ECAP (Equal Channel Angula P ess- ing). In ou a icle, wo di e en pos -p ocessing s a egies we e in es iga ed: (1) low- empe a u e annealing (LTA) and subsequen ECAP p ocessing a 150 ◦ C; (2) no hea ea men and subsequen ECAP p ocessing a 350 ◦ C, 400 ◦ C and 450 ◦ C. The mic os uc u e and mechanical p ope ies o his alloy we e analyzed a each s age o pos - ea men . Me allog aphic obse a ions, combined wi h SEM and EBSD s udies, showed ha he alloys p oduced by SLM ha e a unique cellula mic os uc- u e consis ing o Si ne wo ks su ounding he Al-based ma ix phase. Low- empe a u e annealing (LTA), ollowed by ECAP ea men , acili a ed he mic os uc u al e olu ion o he alloy wi h pa ial b eakup o he Si ne wo k and obse ed nuclea ion o β -Si p ecipi a es h oughou he Al ma ix. This esul ed in a Vicke s mic oha dness o 153 HV and a yield s eng h o 415 MPa. The main esul s show ha pos -p ocessing o SLM-p oduced AlSi10Mg alloys using ECAP signi ican ly a ec s he mic os uc u al e olu ion and mechanical p ope ies o he alloy. Keywo ds: AlSi10Mg alloy; equal channel angula p essing (ECAP); mic os uc u e; mic oha dness; yield s eng h; scanning elec on mic oscopy; elec on backsca e di ac ion (EBSD) 1. In oduc ion App oaches o he ab ica ion o pa s and componen s made o me als and me al alloys ha e aken di e en o ms in ecen yea s. The mos popula app oach o me al pa s o ming, owing o inc easing demand and p oduc i i y, has been me al addi i e manu ac u ing (AM). AM echnology allows he ab ica ion o me allic componen s using me al powde s o wi e ilamen s as s a ing ma e ials. Di e en app oaches o AM, as epo ed in he li e a u e, include ul asonic addi i e manu ac u ing (UAM) [ 1 ], binde je ing [ 2 ], ma e ial je ing [ 3 ], di ec ed ene gy deposi ion (DED) [ 4 ], powde bed usion (PBF) [ 5 ], a pho opolyme iza ion (VP) [ 6 ], e c. Wi h he epo ed success o he PBF app oach in c ea ing e icien pa s o bo h polyme ic and me allic ma e ials [ 7 – 9 ], i has become he mos widely adop ed AM echnology o ad anced unc ional ma e ials p ocessing. PBF uses a hea sou ce om ei he a lase o an elec on beam o o m he desi ed pa by mel ing and joining he powde s o he ma e ial. PBF echnology has been subca ego ized in o echniques including di ec lase me al sin e ing (DLMS) [ 10 ], selec i e lase sin e ing (SLS) [ 11 ], elec on beam mel ing (EBM) [ 12 ], selec i e hea sin e ing (SHS) [ 13 ], and selec i e lase mel ing (SLM) [ 14 ]. SLM uses a Ma e ials 2022,15, 7940. h ps://doi.o g/10.3390/ma15227940 h ps://www.mdpi.com/jou nal/ma e ials Ma e ials 2022,15, 7940 2 o 14 lase beam o mel and join he a omized me allic powde s uni o mly dis ibu ed o e a laye ed building pla o m. Due o i s p ecision and high cooling a e (app ox. 10 8◦ C/s), i is o en he desi ed echnique o building h ee-dimensional pa s and componen s wi h so me als, such as aluminum and i s alloys. In ecen yea s, he Al-based ma ix AlSi10Mg alloy has been g ea ly inco po a ed in i indus ies, such as he au omo i e [ 15 ] and ae ospace indus ies [ 16 ]. The mechanical p ope ies o hese alloys make hem ideal o designing componen s ha can be used in he au omo i e o ae ospace indus ies. Compa ed o he adi ional cas , he SLM- ab ica ed AlSi10Mg alloy has some ad- an ages. I has a he e ogeneous mic os uc u e composed o h ee majo ne wo ks: a cellula ne wo k; a mel pool bounda y ne wo k; and a g ain bounda y ne wo k. The desi able mechanical p ope ies o his alloy, such as s ain ha denabili y and high s eng h, a e de e mined by his unique mic os uc u e. Acco ding o he esea ch wo ks [ 17 , 18 ], a he e ogeneous SLM- ab ica ed AlSi10Mg was ound o possess a wo k ha dening exponen o app oxima ely 0.252, which was almos wice ha o an alloy ab ica ed using powde me allu gy, which had a wo k ha dening exponen o app oxima ely 0.127. Compa ed o an alloy ab ica ed using he g a i y cas me hod, which had a wo k ha dening exponen o app oxima ely 0.1, he SLM- ab ica ed AlSi10Mg is mo e desi able. To inc ease he mechanical pe o mance, he AlSi10Mg alloy is o en pos -p ocessed a - e SLM. Conside ing he plas ic de o ma ion p ocesses, he mos common pos -p ocessing me hod is ho isos a ic p essing [ 19 ]. Howe e , his p ocess leads o a signi ican educ ion in s eng h. To imp o e he mechanical p ope ies o a ious me als, equal channel angula p essing (ECAP) o equal channel angula ex usion (ECAE) a e o en used, mainly because o he e inemen o mic os uc u e and inc eased disloca ion densi y [ 20 – 22 ]. Fo addi- i ely manu ac u ed (AM) pa s, ECAP has ano he ad an age—i can signi ican ly educe hei po osi y [23]. Howe e , his echnique also has some disad an ages: inhomogenei y in s ain dis ibu ion, complica ed ooling, and high labo cos . Al hough he cu en li e a u e add esses pos -p ocessing app oaches based on se e e plas ic de o ma ion (SPD) echniques ha ha e he po en ial o imp o e he mechanical p ope ies o addi i ely manu ac u ed pa s [ 24 – 26 ], a esea ch gap exis s due o he lack o s udies ocusing on pos -p ocessing condi ions such as se e e plas ic de o ma ion a ele- a ed empe a u e, ei he in combina ion o no wi h hea ea men . Mo eo e , due o he no el y o he AM p ocess compa ed o con en ional manu ac u ing me hods, a ho ough s udy on he se e e plas ic de o ma ion o addi i ely manu ac u ed p oduc s is needed. The e o e, he objec i e o his esea ch is o in es iga e he no el pos -p ocessing s a egies o he SLM- ab ica ed AlSi10Mg alloy by s udying he mic os uc u e and he esul ing mechanical p ope ies. The esul s o his esea ch will acili a e he de elopmen o new pos -p ocessing echnologies o SLM-p oduced ab ica ed AlSi10Mg alloys o achie e he desi ed mechanical p ope ies. This will a emp o sho en he pos -p ocessing ime, educe he ECAP wo kload, and b idge he s eng h/duc ili y ade-o o hese alloys epo ed in he li e a u e [22]. 2. Ma e ials and Me hods Gas-a omized AlSi10Mg powde p oduced by Sigma Ald ich was used o ab ica e he samples by he selec i e lase mel ing (SLM) me hod. Be o e being used o p in ing, he la ge and sin e ed pa icles we e sepa a ed by sie ing he powde h ough a sie e wi h a mesh size o 63 µm. SLM samples wi h dimensions 15 × 15 × 50 mm and a nea ly comple e densi y (99.92%) we e ab ica ed using he T uP in 1000 sys em (T ump , Di zingen, Ge many) wi h op imized s anda d pa ame e s (lase powe = 175 W; laye hickness = 20 µ m; scan speed = 1400 mm/s; scan o a ion = 90 ◦ ; A a mosphe e). A sample om SLM was g ound o achie e he inle dimensions o he ECAP ma ix and hen subjec ed o low- empe a u e annealing (LTA) a 280 ◦ C o 9 min. This hea ea men was aimed a pa ially elimina ing esidual s esses, imp o ing upon echnological plas ici y, and modi ying he cellula mic os uc u e. Ma e ials 2022,15, 7940 3 o 14 The wo king samples we e p essed once h ough a 90 ◦ ECAP die (in oducing a s ain o ε = ~1). The ECAP p ocess was pe o med using samples a e annealing and samples ha we e no annealed, a di e en empe a u es. Table 1lis s he wo king samples o his wo k and hei indi idual pos -p ocessing pa ame e s. Table 1. P epa ed samples used o he s udy. Sample ID Annealing ECAP Tempe a u e (◦C) HT280E150 LTA a 280 ◦C 150 SLME350 No annealed 350 SLME400 No annealed 400 SLME450 No annealed 450 SLM No annealed No ECAP HT280 LTA a 280 ◦C No ECAP The LabTes 5.2000 CT hyd aulic p ess (Figu e 1), wi h a maximum am speed o 400 mm/min , was used o he ECAP expe imen . In his con igu a ion, he am speed o he hyd aulic cylinde o he p ess was con olled by oil p essu e wi h he help o a se o al e and an elec ic mo o . Hea ing was con olled by a dTRON 304 de ice equipped wi h a NiC -Ni he mocouple ha could be used up o a maximum empe a u e o 1350 ◦ C. Since he ic ion e ec canno be neglec ed in he ECAP p ocess, a Nic o-The mocup 1200- ype lub ican was used o educe he ic ion coe icien be ween he ECAP sample and he ECAP die. Ma e ials2022,15,xFORPEERREVIEW3o 15   oachie e heinle dimensionso  heECAPma ixand hensubjec ed olow‐ empe a u e annealing(LTA)a 280°C o 9min.Thishea  ea men wasaimeda pa iallyelimina ‐ ing esiduals esses,imp o ingupon echnologicalplas ici y,andmodi ying hecellula  mic os uc u e. Thewo kingsampleswe ep essedonce h ougha90°ECAPdie(in oducinga s aino ε=~1).TheECAPp ocesswaspe o medusingsamplesa e annealingand samples ha we eno annealed,a di e en  empe a u es.Table1lis s hewo kingsam‐ ples o  hiswo kand hei indi idualpos ‐p ocessingpa ame e s. Table1.P epa edsamplesused o  hes udy. SampleIDAnnealing ECAPTempe a u e(°C) HT280E150LTAa 280°C150 SLME350No annealed350 SLME400No annealed400 SLME450No annealed450 SLMNo annealedNoECAP HT280LTAa 280°CNoECAP TheLabTes 5.2000CThyd aulicp ess(Figu e1),wi hamaximum amspeedo 400 mm/min,wasused o  heECAPexpe imen .In hiscon igu a ion, he amspeedo  he hyd auliccylinde o  hep esswascon olledbyoilp essu ewi h hehelpo ase o al eandanelec icmo o .Hea ingwascon olledbyadTRON304de iceequipped wi haNiC ‐Ni he mocouple ha couldbeusedup oamaximum empe a u eo 1350 °C.Since he ic ione ec canno beneglec edin heECAPp ocess,aNic o‐The mocup 1200‐ ypelub ican wasused o educe he ic ioncoe icien be ween heECAPsample and heECAPdie.  Figu e1.Viewo  hewo ks a ion o ma e ial o mingusing heECAPp ocess. Me allog aphicsampleswe ecu  om heuni o mlyde o med egionin heplane con aining heno maldi ec ion(ND)and he ans e sedi ec ion(TD)planeso  he ECAPspecimen o  u he analysis.Me allog aphicp epa a iono  hespecimenp o‐ ceededbyg indingwi hSiCpape s oag i sizeo 1200,polishingwi hacoa sediamond suspensionandmi o polishingwi h0.04μmcolloidalsilica.Fo EBSDanalysis,mi o  polishingwi h0.04μmcolloidalsilicawaspe o med o onehou wi hanMDChem polishingclo h oc ea eas ess‐ eesu ace. Mic os uc u alanalyseswe econduc edbyacombina iono op icalmic oscopy andscanningelec onmic oscopy(SEM)usingaZeissSup a35ins umen equipped wi haEDAXEBSDsys em.Elec onbacksca e di ac ion(EBSD)analysiswaspe ‐ o medwi hanaccele a ing ol ageo 20kV,s epsizeo 0.06μm,anda il angleo 72°. ATEXso wa ewasused oanalyze heEBSDda aand ogene a eo ien a ionmaps,as Figu e 1. View o he wo ks a ion o ma e ial o ming using he ECAP p ocess. Me allog aphic samples we e cu om he uni o mly de o med egion in he plane con aining he no mal di ec ion (ND) and he ans e se di ec ion (TD) planes o he ECAP specimen o u he analysis. Me allog aphic p epa a ion o he specimen p oceeded by g inding wi h SiC pape s o a g i size o 1200, polishing wi h a coa se diamond suspension and mi o polishing wi h 0.04 µ m colloidal silica. Fo EBSD analysis, mi o polishing wi h 0.04 µ m colloidal silica was pe o med o one hou wi h an MD Chem polishing clo h o c ea e a s ess- ee su ace. Mic os uc u al analyses we e conduc ed by a combina ion o op ical mic oscopy and scanning elec on mic oscopy (SEM) using a Zeiss Sup a 35 ins umen equipped wi h a EDAX EBSD sys em. Elec on backsca e di ac ion (EBSD) analysis was pe o med wi h an accele a ing ol age o 20 kV, s ep size o 0.06 µ m, and a il angle o 72 ◦ . ATEX so wa e was used o analyze he EBSD da a and o gene a e o ien a ion maps, as well as o calcula e he GND densi y based on he KAM alues acco ding o me hods published elsewhe e [ 27 ]. Ma e ials 2022,15, 7940 4 o 14 Ha dness measu emen s (H ) we e aken o e a ec angula pa e n o 12 mm ×12 mm dimension (on he c oss-sec ional planes o he specimens) using a mic oha dness es e (Fu u e-Tech FM-ARS), applying a load o 300 g o 15 s. Each inden a ion was made a equal in e als, sepa a ing he poin s a a e ical and ho izon al displacemen o 0.84 mm. 3. Resul s and Discussion 3.1. Mic os uc u e 3.1.1. Mic os uc u e P io o ECAP P ocessing Figu e 2shows op ical mic og aphs o he SLM as buil , as well as HT280 samples. Cha ac e is ic o he mic os uc u e a e he emaining aces o discon inuous lase scans. These aces a e ypically seen in SLM- ab ica ed me allic ma e ials [ 28 ]. As seen in he ligh mic oscopic images, he edges o he lase scan aces a e mo e e ched, o ming an ou line o he scan aces. The ligh mic oscopic images do no p o ide a clea indica ion o he mic os uc u al e olu ion o he LTA specimen compa ed o i s as-buil (SLM) coun e pa . The e o e, a mo e de ailed analysis wi h SEM is equi ed. Ma e ials2022,15,xFORPEERREVIEW4o 15   wellas ocalcula e heGNDdensi ybasedon heKAM aluesacco ding ome hods publishedelsewhe e[27]. Ha dnessmeasu emen s(H )we e akeno e a ec angula pa e no 12mm×12 mmdimension(on hec oss‐sec ionalplaneso  hespecimens)usingamic oha dness es e (Fu u e‐TechFM‐ARS),applyingaloado 300g o 15s.Eachinden a ionwasmade a equalin e als,sepa a ing hepoin sa a e icalandho izon aldisplacemen o 0.84 mm. 3.Resul sandDiscussion 3.1.Mic os uc u e 3.1.1.Mic os uc u eP io  oECAPP ocessing Figu e2showsop icalmic og aphso  heSLMasbuil ,aswellasHT280samples. Cha ac e is ico  hemic os uc u ea e he emaining aceso discon inuouslase scans. These acesa e ypicallyseeninSLM‐ ab ica edme allicma e ials[28].Asseenin he ligh mic oscopicimages, heedgeso  helase scan acesa emo ee ched, o mingan ou line o  hescan aces.Theligh mic oscopicimagesdono p o ideaclea indica ion o  hemic os uc u ale olu iono  heLTAspecimencompa ed oi sas‐buil (SLM)coun‐ e pa .The e o e,amo ede ailedanalysiswi hSEMis equi ed.  (a)(b) Figu e2.Mic os uc u eo sample omligh mic oscopy(a)SLM;(b)HT280. Figu e3shows heSEMimageso  heas‐buil sample(Figu e3a)and heHT280 sample(Figu e3b).Auniquecellula mic os uc u ecanbeseeninbo hsamples.Thecell sizein heLTAsampleissligh lyla ge  han ha o  heSLM‐ ab ica ed(as‐buil )sample. Thecellula s uc u econsis so Sine wo kssu ounding heg ainso  heAlma ix.As canbeseenin heSTEMandHAADFimages(Figu e4),LTAleads opa ialdisin eg a‐ iono  heSine wo ka ound heAlma ixandp ecipi a iono nanoscaleSip ecipi a es whicha e isibleinside hecellula s uc u e.  Figu e 2. Mic os uc u e o sample om ligh mic oscopy (a) SLM; (b) HT280. Figu e 3shows he SEM images o he as-buil sample (Figu e 3a) and he HT280 sample (Figu e 3b). A unique cellula mic os uc u e can be seen in bo h samples. The cell size in he LTA sample is sligh ly la ge han ha o he SLM- ab ica ed (as-buil ) sample. The cellula s uc u e consis s o Si ne wo ks su ounding he g ains o he Al ma ix. As can be seen in he STEM and HAADF images (Figu e 4), LTA leads o pa ial disin eg a ion o he Si ne wo k a ound he Al ma ix and p ecipi a ion o nanoscale Si p ecipi a es which a e isible inside he cellula s uc u e. Ma e ials2022,15,xFORPEERREVIEW5o 15    (a)(b) Figu e3.Mic os uc u eo sample omSEM(a)SLM;(b)HT280.  (a)(b) Figu e4.STEM(a)andHAADF(b)imageso HT280sampleshowinga up u edSine wo kand nanosizedp ecipi a esloca edwi hinaluminumcells. 3.1.2.Mic os uc u ea e ECAPP ocessing Figu e5ashows heop icalmic og apho  hesampleHT280E150.A e chemical e ching, heobse edmic os uc u eshows heso‐called ish‐likesemici cula pa e n [22],whichwas o meddue oECAP‐induced o a iono  hemic os uc u e.A e  he ECAPp ocessingo  heSLMsamples,Figu e5b–d,weseeasimila semici cula mic o‐ s uc u epa e nasin heHT280E150sample.Howe e ,i shouldbeno ed ha  hese pa e nsalmos disappea eda e ECAPp ocessinga  hehighes  empe a u eo 450°C.  Figu e 3. Mic os uc u e o sample om SEM (a) SLM; (b) HT280. Ma e ials 2022,15, 7940 5 o 14 Ma e ials2022,15,xFORPEERREVIEW5o 15    (a)(b) Figu e3.Mic os uc u eo sample omSEM(a)SLM;(b)HT280.  (a)(b) Figu e4.STEM(a)andHAADF(b)imageso HT280sampleshowinga up u edSine wo kand nanosizedp ecipi a esloca edwi hinaluminumcells. 3.1.2.Mic os uc u ea e ECAPP ocessing Figu e5ashows heop icalmic og apho  hesampleHT280E150.A e chemical e ching, heobse edmic os uc u eshows heso‐called ish‐likesemici cula pa e n [22],whichwas o meddue oECAP‐induced o a iono  hemic os uc u e.A e  he ECAPp ocessingo  heSLMsamples,Figu e5b–d,weseeasimila semici cula mic o‐ s uc u epa e nasin heHT280E150sample.Howe e ,i shouldbeno ed ha  hese pa e nsalmos disappea eda e ECAPp ocessinga  hehighes  empe a u eo 450°C.  Figu e 4. STEM ( a ) and HAADF ( b ) images o HT280 sample showing a up u ed Si ne wo k and nanosized p ecipi a es loca ed wi hin aluminum cells. 3.1.2. Mic os uc u e a e ECAP P ocessing Figu e 5a shows he op ical mic og aph o he sample HT280E150. A e chemical e ching, he obse ed mic os uc u e shows he so-called ish-like semici cula pa e n [ 22 ], which was o med due o ECAP-induced o a ion o he mic os uc u e. A e he ECAP p ocessing o he SLM samples, Figu e 5b–d, we see a simila semici cula mic os uc u e pa e n as in he HT280E150 sample. Howe e , i should be no ed ha hese pa e ns almos disappea ed a e ECAP p ocessing a he highes empe a u e o 450 ◦C. Ma e ials2022,15,xFORPEERREVIEW6o 15    (a)(b)  (c)(d) Figu e5.Mic os uc u eso ECAP‐p ocessedsamples(a)HT280E150;(b)SLME350;(c)SLME400; (d)SLME450. Tocla i yhow hede o ma ion empe a u ea ec s hecellula Sine wo k,weac‐ qui edseconda yelec onimagesa highe magni ica ion.Figu e6ashows heSEMim‐ ageo  heHT280E150sample.I canbeseen ha ,a e ECAPp essinga 150°C, hecel‐ lula s uc u eshowninFigu e3bismo eb okenandcoa se .TheSip ecipi a esinside hecellsha ee ol ed ompoin ‐like o od‐like.InFigu e6b,wesee ha ECAPin o‐ ducedahighdisloca ion,whichp o idedagoodoppo uni y o nuclea iono p ecipi‐ a esondisloca ionco es, esul ingincomple edisin eg a iono  hecellula Sine wo k [29].  Figu e 5. Mic os uc u es o ECAP-p ocessed samples ( a ) HT280E150; ( b ) SLME350; ( c ) SLME400; (d) SLME450. Ma e ials 2022,15, 7940 6 o 14 To cla i y how he de o ma ion empe a u e a ec s he cellula Si ne wo k, we acqui ed seconda y elec on images a highe magni ica ion. Figu e 6a shows he SEM image o he HT280E150 sample. I can be seen ha , a e ECAP p essing a 150 ◦ C, he cellula s uc u e shown in Figu e 3b is mo e b oken and coa se . The Si p ecipi a es inside he cells ha e e ol ed om poin -like o od-like. In Figu e 6b, we see ha ECAP in oduced a high disloca ion, which p o ided a good oppo uni y o nuclea ion o p ecipi a es on disloca ion co es, esul ing in comple e disin eg a ion o he cellula Si ne wo k [29]. Ma e ials2022,15,xFORPEERREVIEW7o 15    (a)(b)  (c)(d) Figu e6.SEMimageso ECAP‐p ocessedsamples(a)HT280E150;(b)SLME350;(c)SLME400;(d) SLME450. A e ECAPde o ma iona highe  empe a u eso 400°Cand450°C,wesee he uni o mdis ibu iono la geSipa iclesin hemic os uc u e,seeFigu e6c,d.Compa ed wi hSLME350sample, hedis ancesbe weenSipa iclesa elonge in heSLME400and SLME450samples,and henumbe o Sipa iclessigni ican lydec eases. In hes udy[30],i ispos ula ed ha  heb eakupo Sine wo ksand he o ma ion o coa se Sipa iclesisdue o hep esenceo excessSip ecipi a esin hesupe sa u a ed Al‐basedma ix.I canbeconcluded ha ,a e hea  ea men , hesupe sa u a edSia ‐ omsa e epelled om heAlma ixand o mnewsmallSipa icles,whicha eini ially dis ibu edwi hin hecellula Sine wo k.Since hewo kpiecesa es a icallyannealedin heECAPdiechanneldu ingp ocessing, he eissu icien  ime o  he o ma iono  coa se pa icles,whosesizeinc easeswi hinc easingde o ma ion empe a u e.Theob‐ se edmic os uc u ale olu iono  hes udiedsamplesa e ECAPp ocessinga di e ‐ en  empe a u esisinlinewi h heobse a ions epo edby hese esea che s[22,27].On hemac oscale, he heo e icalshea de o ma ionpa e nisin hesamedi ec ionas he lowlines’ angen ,ina e icalalignmen  o heplaneo channelsin e sec ion.Comp es‐ sionis he e o eequallydis ibu edin he ans e sedi ec ionand heex usiondi ec ion. On heno maldi ec ion– ans e sedi ec ion(ND–TD)plane, hisisseenasapa allel se ieso mac oscopicbands.Thisis hemos signi ican  eason o  heobse a iono sem‐ ici cula pa e nsandelonga eds uc u esin hemic os uc u e. Elec onbacksca e di ac ion(EBSD)analysiswaspe o med op o ide u he  de ailson hee olu iono  hemic os uc u e.Figu e7shows hein e sepole igu e(IPF‐ Z)maps akenin hex–yplane(c oss‐sec ionalplane) o  heECAP‐p ocessedsamples. In his igu e, he edlinesco espond olow‐angleg ainbounda ies(LAGBs)and he g eenlinesco espond ohigh‐angleg ainbounda ies(HAGBs). Figu e 6. SEM images o ECAP-p ocessed samples ( a ) HT280E150; ( b ) SLME350; ( c ) SLME400; (d) SLME450. A e ECAP de o ma ion a highe empe a u es o 400 ◦ C and 450 ◦ C, we see he uni o m dis ibu ion o la ge Si pa icles in he mic os uc u e, see Figu e 6c,d. Compa ed wi h SLME350 sample, he dis ances be ween Si pa icles a e longe in he SLME400 and SLME450 samples, and he numbe o Si pa icles signi ican ly dec eases. In he s udy [ 30 ], i is pos ula ed ha he b eakup o Si ne wo ks and he o ma ion o coa se Si pa icles is due o he p esence o excess Si p ecipi a es in he supe sa u a ed Al-based ma ix. I can be concluded ha , a e hea ea men , he supe sa u a ed Si a oms a e epelled om he Al ma ix and o m new small Si pa icles, which a e ini ially dis ibu ed wi hin he cellula Si ne wo k. Since he wo kpieces a e s a ically annealed in he ECAP die channel du ing p ocessing, he e is su icien ime o he o ma ion o coa se pa icles, whose size inc eases wi h inc easing de o ma ion empe a u e. The ob- se ed mic os uc u al e olu ion o he s udied samples a e ECAP p ocessing a di e en empe a u es is in line wi h he obse a ions epo ed by hese esea che s [ 22 , 27 ]. On he mac oscale, he heo e ical shea de o ma ion pa e n is in he same di ec ion as he low lines’ angen , in a e ical alignmen o he plane o channels in e sec ion. Comp ession is he e o e equally dis ibu ed in he ans e se di ec ion and he ex usion di ec ion. On he Ma e ials 2022,15, 7940 7 o 14 no mal di ec ion– ans e se di ec ion (ND–TD) plane, his is seen as a pa allel se ies o mac oscopic bands. This is he mos signi ican eason o he obse a ion o semici cula pa e ns and elonga ed s uc u es in he mic os uc u e. Elec on backsca e di ac ion (EBSD) analysis was pe o med o p o ide u he de ails on he e olu ion o he mic os uc u e. Figu e 7shows he in e se pole igu e (IPF-Z) maps aken in he x–y plane (c oss-sec ional plane) o he ECAP-p ocessed samples. In his igu e, he ed lines co espond o low-angle g ain bounda ies (LAGBs) and he g een lines co espond o high-angle g ain bounda ies (HAGBs). Ma e ials2022,15,xFORPEERREVIEW8o 15    (a)(b)  (c)(d) Figu e7.SEMIPF‐Zimageso ECAP‐p ocessedsamples(a)HT280E150;(b)SLME350;(c)SLME400; (d)SLME450. F omFigu e7aand heda ainTable2,i canbeseen ha sampleHT280E150hasan ul a ine‐g aineds uc u e.Themeasu eda e ageg ainsizeis0.43μm.Fo  hissample, heEBSDanalysisalsoshowsa ela i elyhighpe cen ageo LAGBs(abou 55%),indica ‐ ing he o ma ionandaccumula iono mul ipledisloca ionsin hemic os uc u e. Table2.Mic os uc u alpa ame e sob ained omEBSDanalysis. SampleG ainSize,μmLowAngleBounda‐ ies,% HighAngleBounda‐ ies,%GNDsDensi y,m −2  HT280E1500.44±0.0655.2±1.344.8±1.26.70×10 14 ±0.14 SLME3503.37±0.0837.7±1.162.3±1.49.60×10 13 ±0.12 SLME4002.11±0.0838.0±1.262.0±1.37.69×10 13 ±0.16 SLME4502.91±0.0747.5±1.552.5±1.36.88×10 13 ±0.20 Figu e 7. SEM IPF-Z images o ECAP-p ocessed samples ( a ) HT280E150; ( b ) SLME350; ( c ) SLME400; (d) SLME450. F om Figu e 7a and he da a in Table 2, i can be seen ha sample HT280E150 has an ul a ine-g ained s uc u e. The measu ed a e age g ain size is 0.43 µ m. Fo his sample, he EBSD analysis also shows a ela i ely high pe cen age o LAGBs (abou 55%), indica ing he o ma ion and accumula ion o mul iple disloca ions in he mic os uc u e. Ma e ials 2022,15, 7940 8 o 14 Table 2. Mic os uc u al pa ame e s ob ained om EBSD analysis. Sample G ain Size, µmLow Angle Bounda ies, % High Angle Bounda ies, % GNDs Densi y, m−2 HT280E150 0.44 ±0.06 55.2 ±1.3 44.8 ±1.2 6.70 ×1014 ±0.14 SLME350 3.37 ±0.08 37.7 ±1.1 62.3 ±1.4 9.60 ×1013 ±0.12 SLME400 2.11 ±0.08 38.0 ±1.2 62.0 ±1.3 7.69 ×1013 ±0.16 SLME450 2.91 ±0.07 47.5 ±1.5 52.5 ±1.3 6.88 ×1013 ±0.20 In con as , he IPF-Z image o he SLME350 sample in Figu e 7b shows ela i ely la ge (columna ) g ains, abou six imes la ge han hose o he HT280E150 sample. In he case o his sample, he measu ed a e age g ain size is abou 3.3 µ m. In e es ingly, ce ain a eas o ine g ains can be obse ed in he IPF mapping along a cu ed egion ha has he exac cha ac e is ics o he mel pool (hea -a ec ed zone). Taking in o accoun he g ain bounda y (GB) miso ien a ion, sample SLM350 is cha ac e ized by a much lowe pe cen age o LAGBs o 37.7%, indica ing ec ys alliza ion phenomena. ECAP p ocessing a a highe empe a u e o 400 ◦ C esul s in mo e e ec i e e inemen o he mic os uc u e. In he case o he SLME400 sample, he a e age g ain size is abou 2.1 µ m, which ep esen s a 37.4% educ ion compa ed o he SLME350 sample (Figu e 7c). Howe e , he popula ion o LAGBs and HAGBs emains almos he same in bo h samples. ECAP p ocessing a he highes empe a u e o 450 ◦ C, as shown in Figu e 7d, changes he g ain s uc u e o he alloy subs an ially. The bounda ies o he mel pool a e no longe ob ious, and a la ge numbe o small g ains disappea a he bounda ies. Compa ed o he SLME400 sample, he g ain size inc eases by 38.5% o app oxima ely 2.9 µ m. A he same ime, he popula ion o LAGBs also inc eases o 47.5%. Maps o he geome ically necessa y dis ibu ion (GND) o he samples p ocessed ia ECAP a e shown in Figu e 8. The ligh e a eas in he GND maps co espond o he a eas wi h highe disloca ion densi y. As can be seen, sample HT280E150 has he highes GND densi y o 6.70 × 10 14 m −2 . Fo he non-hea - ea ed samples, SLME350 exhibi s a GND densi y o 9.60 × 10 13 m −2 . The SLME400 sample has a GND densi y o 7.69 × 10 13 m −2 , which is abou a 20% educ ion in GND densi y in compa ison wi h he SLME350 sample. The GND densi y o he SLME450 sample is also educed by abou 11% o 6.88 × 10 13 m −2 compa ed o he SLME400 sample, con i ming ha he de o ma ion empe a u e as well as he ini ial mic os uc u e has a signi ican e ec on disloca ion accumula ion. The o ma ion o low-angle g ain bounda ies in aluminum alloys is closely ela ed o he p esence disloca ions [ 31 ]. Du ing ECAP p ocessing, a la ge shea s ain is in o- duced in o he ma e ial, esul ing in an o e all inc ease in disloca ion densi y. Since he mic os uc u e o he SLM alloy is he e ogeneous (i consis s o so Al and ha d Si phases), la ge amoun s o geome ically necessa y disloca ions a e gene a ed o accommoda e he plas ic s ain g adien ha de elops nea he Al/Si in e ace [ 32 ]. These GNDs mo e in o con igu a ions ha a e mo e ene ge ically a o able. The esul is he o ma ion o zones wi h high disloca ion concen a ions, which appea in he o m o LAGBs. In he case o sample HT280E150, he nea ly ull-cellula Al/Si ne wo k allowed he s o age o mo e GNDs, esul ing in he o ma ion o mul iple LAGBs. The IPF-Z and GNDs maps in Figu es 7and 8con i m he highes disloca ion densi y in he s udied a eas o sample HT280E150 compa ed o he o he ECAP-p ocessed samples. This explains why he alue o GNDs densi y was he highes in his sample compa ed o he o he samples. Ma e ials 2022,15, 7940 9 o 14 Ma e ials2022,15,xFORPEERREVIEW10o 15    (a)(b)  (c)(d) Figu e8.GNDsmapso ECAP‐p ocessedsamples(a)HT280E150;(b)SLME350;(c)SLME400;(d) SLME450. The o ma iono low‐angleg ainbounda iesinaluminumalloysisclosely ela ed o hep esencedisloca ions[31].Du ingECAPp ocessing,ala geshea s ainisin oduced in o hema e ial, esul inginano e allinc easeindisloca iondensi y.Since hemic o‐ s uc u eo  heSLMalloyishe e ogeneous(i consis so so Alandha dSiphases),la ge amoun so geome icallynecessa ydisloca ionsa egene a ed oaccommoda e heplas‐ ics aing adien  ha de elopsnea  heAl/Siin e ace[32].TheseGNDsmo ein ocon‐ igu a ions ha a emo eene ge ically a o able.The esul is he o ma iono zoneswi h highdisloca ionconcen a ions,whichappea in he o mo LAGBs.In hecaseo sample HT280E150, henea ly ull‐cellula Al/Sine wo kallowed hes o ageo mo eGNDs, e‐ sul ingin he o ma iono mul ipleLAGBs.TheIPF‐ZandGNDsmapsinFigu es7and Figu e 8. GNDs maps o ECAP-p ocessed samples ( a ) HT280E150; ( b ) SLME350; ( c ) SLME400; (d) SLME450. 3.2. Mechanical P ope ies The oom- empe a u e mechanical p ope ies o he s udied AlSi10Mg samples we e e alua ed by Vicke s mic oha dness and comp ession es s. These es s we e pe o med on samples immedia ely a e SLM ab ica ion (sample SLM), immedia ely a e hea ea men (sample HT280), and a e pos -p ocessing ia ECAP. Figu e 9shows he Vicke s mic oha dness maps. Acco ding o Figu e 9a and he s a is ical da a in Table 3, he a e age mic oha dness o he SLM sample is abou 142 HV. A e low- empe a u e annealing (HT280 sample), mic oha dness dec eases by abou 3% o 138 HV (Figu e 9b) due o s ess elie and pa ial up u e o eu ec ic Si ne wo k.