Electron beam welding of AlCoCrFeNi2.1 high entropy alloy to EN 1.4301 austenitic steel

Con en om his wo k may be used unde he e ms o heC ea i eCommonsA ibu ion 3.0 licence. Any u he dis ibu ion o his wo k mus main ain a ibu ion o he au ho (s) and he i le o he wo k, jou nal ci a ion and DOI. Published unde licence by IOP Publishing L d 14 h In e na ional Con e ence on Elec on Beam Technologies (EBT 2022) Jou nal o Physics: Con e ence Se ies 2443 (2023) 012009 IOP Publishing doi:10.1088/1742-6596/2443/1/012009 1 Elec on beam welding o AlCoC FeNi2.1 high en opy alloy o EN 1.4301 aus eni ic s eel J Rončák1, O Adam2 and M Zobač1 1Ins i u e o Scien i ic Ins umen s o he CAS, B no, Czech Republic 2B no Uni e si y o Technology, Ins i u e o Ma e ials Science and Enginee ing, B no, Czech Republic e-mail: oncak@isib no.cz; ond ej.adam@ u b .cz; [email p o ec ed] Abs ac . Eu ec ic high-en opy alloys (EHEA), also known as mul i-p inciple componen alloys (MPCA), a e a g oup o ma e ials exhibi ing p omising mechanical p ope ies. The p inciple o he alloy is o achie e su icien duc ili y due o he p esence o he so phase and, a he same ime, inc eased s eng h due o he ha d phase. In o de o he newly disco e ed ypes o ma e ials o be used comme cially, i is necessa y o e i y hei beha iou in echnological ope a ions such as welding p ocesses. The e o e, he objec i e o he expe imen was o e alua e he he e ogeneous welded join o he AlCoC FeNi2.1 alloy wi h comme cially used aus eni ic s eel EN 1.4301 by elec on beam welding. The pa ame e s used du ing he p ocess we e p e iously e i ied on homogeneous join s. Subsequen obse a ions we e made by ligh and elec on mic oscopy supplemen ed by chemical analysis. The mechanical p ope ies o he o med join we e e i ied by a Vicke s ha dness es . 1. In oduc ion High en opy alloys ha e g adually become known o he scien i ic communi y as a new concep o p omising ma e ials. Thei disco e y is a ibu ed o p o esso s Can o and Yeh, who in 2004 independen ly p esen ed he esul s o hei esea ch in his a ea. Despi e his ac , examples occu ed be o e he gi en yea , such as pla inum alloys. High en opy alloys a e de ined as ma e ials con aining i e o mo e chemical elemen s, whe e each elemen is con ained in a leas 5 a . % (speci ically in he ange o 5 o 35 a . %). The inc eased numbe o p ima y elemen s should consequen ly ensu e an inc eased mixed en opy o he solid solu ion and p e en he o ma ion o in e me allic phases, which esul s in a single-phase s able s uc u e. This concep p o ed o be w ong, and he men ioned s uc u e loses i s s abili y a e mechanical s ess a ele a ed empe a u es. Howe e , he o ma ion o a mul iphase s uc u e opens new possibili ies in e ms o he de elopmen and use o alloys, such as eu ec ic high en opy alloys [1, 2]. Eu ec ic high en opy alloys (EHEAs), o med p ima ily by a wo-phase s uc u e, a e one o he HEA subg oups combining inc eased s eng h and a he same ime su icien duc ili y. Alloys mos ly con ain ansi ion me als such as Co, C , Fe, Ni, and Mn. The emaining chemical elemen s, such as Al o Ti, occu ing in smalle quan i ies a e supplemen ed as needed. One o such alloys is AlCoC FeNi2.1, whose lamella eu ec ic is o med by a mix u e o so and duc ile FCC and ha d B2 phases [3, 4]. In addi ion o a o able mechanical p ope ies [5, 6], hey a e cha ac e ized by excellen cas abili y, which con ibu es o he idea o u u e use in indus y. Howe e , o be able o use high en opy ma e ials, 14 h In e na ional Con e ence on Elec on Beam Technologies (EBT 2022) Jou nal o Physics: Con e ence Se ies 2443 (2023) 012009 IOP Publishing doi:10.1088/1742-6596/2443/1/012009 2 i is necessa y o e i y hei echnological p ope ies. The e o e, we decided o e alua e dissimila usion welding wi h comme cially used aus eni ic s ainless s eel EN 1.4301 [1]. Aus eni ic s eels a e he mos used ypes o s ainless s eels o comme cial use. Wi hou cold wo king, hey ha e only a e age mechanical p ope ies. Howe e , hey compensa e o his sho coming wi h hei esis ance o co osion in agg essi e en i onmen s. The mos common o he men ioned s eels is EN 1.4301 (AISI 304), also known as 18-8, e e ing o 18 w . % C and 8 w . % Ni wi h ully aus eni ic mic os uc u e. One o he a o able p ope ies is also weldabili y, which p ede e mines EN 1.4301 as s eel o welds o dissimila ma e ials [7, 8]. To c ea e a usion weld om he abo e-men ioned ma e ials, elec on beam welding was used. The echnology elies on emel ing he ma e ial by a high ene gy densi y elec on beam in a acuum chambe . As a esul , he e is no chemical eac ion a ele a ed empe a u es, and elec ons do no lose hei ene gy by in e ac ing wi h he pa icles con ained in he a mosphe e. I is used p ima ily in indus ies wi h highe demands on he homogenei y o he welded join , mechanical p ope ies, and he pu i y o he mic os uc u e [9, 10]. The main objec i e o he s udy was o e alua e a dissimila welded join o AlCoC FeNi2.1 and EN 1.4301 alloys (AISI 304) using: • mac oscopic obse a ion o he weld in e ms o dep h and wid h o he emel ed laye , he p esence o hea -a ec ed zone, • e alua ion o he su icien mixing o chemical elemen s using EDS analysis and he esul ing mechanical p ope ies unde he selec ed pa ame e s. 2. Ma e ials, pa ame e s and e alua ion me hods The AlCoC FeNi2.1 alloy (EHEA) was p epa ed by mel ing in an Indu he m MC 15 induc ion u nace unde educed p essu e in an a gon a mosphe e. Unlike p e ious esea ch, ou aim was o simula e condi ions ha a e close o indus ial p oduc ion. The e o e, no only pu e me als we e used o he p oduc ion, bu a di e en alloy con aining Co, C , Fe, and Ni was emel ed. Subsequen ly, he necessa y alloying wi h pu e me als was pe o med o achie e he equi ed chemical composi ion. A one- ime emel ing was ca ied ou , which was ollowed by he cas ing in o a coppe mold. The esul a e machining was a cylind ical ingo wi h a diame e o 14 mm and a heigh o 28 mm. S ainless aus eni ic s eel EN 1.4301 (SAS) was comme cially pu chased in he o m o a cylind ical ingo wi h a diame e o 16 mm and machined acco ding o he dimensions o a high en opy alloy. A compa ison o he ideal and inal chemical composi ion o bo h ma e ials de e mined by EDS analysis can be seen in able 1. Al hough he alloy name AlCoC FeNi2.1 is based on he a omic a io o he indi idual elemen s, he con en in w . % is used o be e compa ison wi h comme cially used EN 1.4301. The p esence o silicon in he esul ing chemical composi ion o AlCoC FeNi2.1 is due o i s p esence in he emel ed o iginal alloy used o p oduce he high en opy alloy. Table 1. Ideal and inal chemical composi ions o AlCoC FeNi2.1 and EN 1.4301. Composi ion Chemical elemen s in w . % Al Co C Fe Ni Si Mn Ideal EHEA 8.5 18.6 16.4 17.6 38.9 - - Final EHEA 9.5 18.6 14.0 17.4 39.9 0.7 - Ideal SAS - - 18.0 - 20.0 Balance 8.0 - 10.0 0 - 1.0 0 - 2.0 Final SAS - - 18.7 70.5 8.2 0.4 1.9 The ab ica ed ma e ial samples we e cleaned by ul asonica ion in isop opyl alcohol and subjec ed o a usion welding p ocess using a MEBW 60/2-E mic o elec on beam welde ( igu e 1). The de ice has a ully digi al con ol wi h a maximum powe o 2 kW and an accele a ing ol age o 60 kV. The 14 h In e na ional Con e ence on Elec on Beam Technologies (EBT 2022) Jou nal o Physics: Con e ence Se ies 2443 (2023) 012009 IOP Publishing doi:10.1088/1742-6596/2443/1/012009 3 wo king p essu e in he chambe du ing welding is be e han 4 × 10-2 Pa. Welding was p eceded by pa ial joining o ma e ials using s i ches a ou loca ions o p e en possible misalignmen . The selec ed s i ching and welding pa ame e s can be seen in able 2. Figu e 1. Mic o elec on beam welde MEBW 60/2-E. The las pa o he expe imen was o e alua e he esul s o he welding p ocess. The usion-welded ma e ials we e cu using a me allog aphic saw and he sample was p epa ed by sequen ial g inding and polishing o obse a ion in a ligh (Zeiss Axio Obse e 7) and elec on mic oscope (FEG SEM Zeiss Ul a plus). Subsequen ly, a chemical analysis (FEG SEM Zeiss Ul a Plus) was pe o med using lines in se e al a eas o he weld. The app oxima e lines o he measu emen s used o he e alua ion o he chemical composi ion a e indica ed in igu e 2. The mechanical p ope ies we e e i ied by he Vicke s ha dness es HV0.2 (Qness Q10A) wi h a load o 0.2 kg o 10 seconds. Table 2. Pa ame e s o s i ching and welding o dissimila alloys. P ocess Pa ame e s o welding Beam Cu en (mA) Accele a ing Vol age (kV) Welding Speed (mm/s) F equency o Wobbling (Hz) Hea Inpu (J/mm) S i ching 1.5 55 10 - 8.25 Welding 10 55 10 500 55 3. Resul s and discussion Figu e 2 shows he mac os uc u e o he o med weld join wi h a shape simila o ha o a nail o a wine glass be o e e ching. Hence, he hea -a ec ed zone (HAZ) is no isible. The wid h o he usion zone (FZ) is app oxima ely 1.4 mm in he op, 0.6 mm in he uppe hi d and he dep h is 4.4 mm ( igu e 2). I ypically occu s in high ene gy densi y welding when a apid inc ease in empe a u e esul s in mel ing deepe in o he ma e ial. The gi en shape he e o e con i ms a co ec beam ocusing. A he same ime, i is clea om he mac oscopic iew ha he mel ing p ocess p oceeded di e en ly depending on he base ma e ial. The igh side (EHEA) shows a la ge emel ing a ea a he op o he weld compa ed o he le side (SAS). This is due o he di e en he mophysical p ope ies. Compa ed o comme cially p oduced 1.4301, high en opy alloys a e unde s udied in e ms o he mophysical p ope ies. The e o e, i is no possible o compa e he p ope ies wi hin he expe imen . 14 h In e na ional Con e ence on Elec on Beam Technologies (EBT 2022) Jou nal o Physics: Con e ence Se ies 2443 (2023) 012009 IOP Publishing doi:10.1088/1742-6596/2443/1/012009 4 Figu e 2. Dissimila weld join . In addi ion o he esul ing shape, a en ion mus also be paid o de ec s loca ed in he usion zone. These a e he po es a he bo om o he weld nea he oo . Thei p esence ad e sely a ec s he mechanical p ope ies and is pa ly in luenced by he chosen pa ame e s, namely he welding speed. A high speed, he e apo a ed alloys emain apped in he apidly cooled mic os uc u e. In he ollowing es s i is he e o e necessa y o e i y he dependence o he p esence o de ec s on speci ic welding pa ame e s. Mac oscopic obse a ions we e ollowed by chemical analysis using he EDS me hod. The i s pa o he analysis consis ed o checking he abundance o chemical elemen s om one base ma e ial o ano he ( igu e 3). The second pa e alua ed he p esence o elemen s in he join om op o bo om ( igu e 4). Al hough o he elemen s (Al, Co, Si, Mn) we e p esen in he ma e ial acco ding o he analysis, Fe, Ni, and C we e selec ed o he esul ing plo s. The e ec o silicon on he weldabili y o he welded join was no he subjec o he expe imen ; howe e , because o i s equen use in cas alloys, i is app op ia e o conside his in luence in u u e es s. Figu e 3. Chemical composi ion ac oss he usion zone and base ma e ials. 0,0 20,0 40,0 60,0 80,0 0,0 0,5 1,0 1,5 Chemical composi ion [w . %] Dis ance [mm] SAS FZ EHEA Fe w % C w % Ni w % 14 h In e na ional Con e ence on Elec on Beam Technologies (EBT 2022) Jou nal o Physics: Con e ence Se ies 2443 (2023) 012009 IOP Publishing doi:10.1088/1742-6596/2443/1/012009 5 The analysis shown in igu e 3 in he o m o a simple mo ing a e age con i ms he success ul mixing o he chemical elemen s con ained in bo h base ma e ials. Thus, he e was no mo emen du ing he mel ing p ocess and, om a s uc u al poin o iew, he base ma e ials we e p epa ed app op ia ely. A he same ime, he s i ching ha p eceded he usion welding also p o ed o be e icien . Chemical elemen s con ained only in he weld join ( igu e 4) addi ionally shows ha he chemical composi ion does no a y signi ican ly h oughou he e alua ed a ea and he mic os uc u e o he usion zone is likely o be s able. Howe e , in e ms o phase composi ion, i would be necessa y o complemen he expe imen wi h EBSD o X- ay analysis. Figu e 4. Chemical composi ion along he usion zone. The las pa o he e alua ion o he he e ogeneous welded join consis ed o he Vicke s HV0.2 ha dness es . Figu e 5 shows he alues measu ed a he op o he weld join and he base ma e ials. The es ed dis ance was 5 millime e s wi h a spacing o 0.25 mm be ween inden a ion poin s. The e was a signi ican dec ease in he mechanical p ope ies o he usion zone. A he same ime, a dec ease in ha dness alues o SAS was caused by g ain coa sening e i ied by obse a ion in an elec on mic oscope. The gi en ac s con i m he p esence o a hea -a ec ed zone. Figu e 5. Ha dness alues o he base ma e ials and he usion zone. In he case o he high en opy alloy, on he con a y, he e was a sligh inc ease in ha dness in he hea -a ec ed zone compa able in size o ha o he SAS. Undesi able e ec o highe ha dness is p obably due o he highe hea inpu in he base ma e ial. In addi ion o he p esence o de ec s, u u e es s will also e i y he sui abili y o he pa ame e s in e ms o he magni ude o he hea inpu . 0 10 20 30 40 50 60 0,0 0,5 1,0 1,5 2,0 2,5 3,0 Chemical composi ion [w . %] Dis ance [mm] Fe w % Ni w % C w % 150 200 250 300 350 400 450 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Ha dness HV0.2 [-] Inden a ion poin s [-] FZ SAS 1.4301 EHEA HAZ HAZ 14 h In e na ional Con e ence on Elec on Beam Technologies (EBT 2022) Jou nal o Physics: Con e ence Se ies 2443 (2023) 012009 IOP Publishing doi:10.1088/1742-6596/2443/1/012009 6 4. Conclusion A he e ogeneous weld join o comme cially used s ainless aus eni ic s eel EN 1.4301 (AISI 304) and cas high en opy alloy AlCoC FeNi2.1 was o med by elec on beam welding and e alua ed by ma e ials enginee ing me hods. Obse a ion o he mac os uc u e, chemical composi ion and ha dness o he ma e ial led o he ollowing indings: • Weld join 1.4 mm wide a he op, 0.6 mm wide in he uppe hi d and app oxima ely 4.4 mm deep was o med using he selec ed pa ame e s. • De ec s we e p esen in he o m o po es in he bo om pa , which can ad e sely a ec he mechanical p ope ies. • Chemical analysis o he usion zone showed a success ul mixing o bo h base ma e ials. • The ha dness es and obse a ion in an elec on mic oscope e ealed he p esence o hea - a ec ed zones. Indi idual indings show ha joining wo selec ed dissimila ma e ials by elec on beam welding is possible. Howe e , u he es s need o be ca ied ou o gua an ee su icien mechanical s eng h and he absence o de ec s in he mac o- and mic os uc u e. Acknowledgemen s The a icle was c ea ed wi h he ins i u ional suppo o RVO:68081731. 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