The current investigation of refill friction stir spot welding(refill FSSW)Al alloy to copper primarily involved plunging the tool into bottom copper sheet to achieve both metallurgical and mechanical interfacial bond...The current investigation of refill friction stir spot welding(refill FSSW)Al alloy to copper primarily involved plunging the tool into bottom copper sheet to achieve both metallurgical and mechanical interfacial bonding.Compared to conventional FSSW and pinless FSSW,weld strength can be significantly improved by using this method.Nevertheless,tool wear is a critical issue during refill FSSW.In this study,defect-free Al/copper dissimilar welds were successfully fabricated using refill FSSW by only plunging the tool into top Al alloy sheet.Overall,two types of continuous and ultra-thin intermetallic compounds(IMCs)layers were identified at the whole Al/copper interface.Also,strong evidence of melting and resolidification was observed in the localized region.The peak temperature obtained at the center of Al/copper interface was 591℃,and the heating rate reached up to 916℃/s during the sleeve penetration phase.A softened weld region was produced via refill FSSW process,the hardness profile exhibited a W-shaped appearance along middle thickness of top Al alloy.The weld lap shear load was insensitive to the welding condition,whose scatter was rather small.The fracture path exclusively propagated along the IMCs layer of Cu_(9)Al_(4) under the external lap shear loadings,both CuAl_(2) and Cu_(9)Al_(4) were detected on the fractured surface on the copper side.This research indicated that acceptable weld strength can be achieved via pure metallurgical joining mechanism,which has significant potential for the industrial applications.展开更多
Friction stir processing(FSP)was employed as a post-printing surface modification technique to enhance surface properties of arc-directed energy deposited 316 L austenitic stainless-steel parts.Corrosion properties an...Friction stir processing(FSP)was employed as a post-printing surface modification technique to enhance surface properties of arc-directed energy deposited 316 L austenitic stainless-steel parts.Corrosion properties and passivity of stir zone and base metal were investigated in 3.5 wt.%NaCl solution.Results reveal a gradual improvement in corrosion protection ability of formed passive film on the alloy's surface over time.Specifically,FSPed region exhibited superior passive behavior and uniform corrosion resistance compared to base metal.This improvement was attributed to a more homogeneous microstructure of stir zone,which hindered micro-galvanic coupling effect.However,it was observed that FSP-treatment did not effectively impede the propagation of pitting corrosion.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51975479,51905437)Fundamental Research Funds for the Central Universities(Grant No.3102019QD0404)+1 种基金Science and Technology Bureau of Yulin(Grant No.2019-86-1)High-Level Talent Project of Yulin University,China(Grant No.20GK06).
文摘The current investigation of refill friction stir spot welding(refill FSSW)Al alloy to copper primarily involved plunging the tool into bottom copper sheet to achieve both metallurgical and mechanical interfacial bonding.Compared to conventional FSSW and pinless FSSW,weld strength can be significantly improved by using this method.Nevertheless,tool wear is a critical issue during refill FSSW.In this study,defect-free Al/copper dissimilar welds were successfully fabricated using refill FSSW by only plunging the tool into top Al alloy sheet.Overall,two types of continuous and ultra-thin intermetallic compounds(IMCs)layers were identified at the whole Al/copper interface.Also,strong evidence of melting and resolidification was observed in the localized region.The peak temperature obtained at the center of Al/copper interface was 591℃,and the heating rate reached up to 916℃/s during the sleeve penetration phase.A softened weld region was produced via refill FSSW process,the hardness profile exhibited a W-shaped appearance along middle thickness of top Al alloy.The weld lap shear load was insensitive to the welding condition,whose scatter was rather small.The fracture path exclusively propagated along the IMCs layer of Cu_(9)Al_(4) under the external lap shear loadings,both CuAl_(2) and Cu_(9)Al_(4) were detected on the fractured surface on the copper side.This research indicated that acceptable weld strength can be achieved via pure metallurgical joining mechanism,which has significant potential for the industrial applications.
基金the support provided by the Natural Sciences and Engineering Research Council of Canada(NSERC)[grant number RGPIN-2017–04368]the Canada Research Chair program[grant number CRC-2019–00017],Ocean Frontier Institute,and Dalhousie University in making this work possiblethe Herff College of Engineering at the University of Memphis for the financial support of the research through the HCOE-FRG program
文摘Friction stir processing(FSP)was employed as a post-printing surface modification technique to enhance surface properties of arc-directed energy deposited 316 L austenitic stainless-steel parts.Corrosion properties and passivity of stir zone and base metal were investigated in 3.5 wt.%NaCl solution.Results reveal a gradual improvement in corrosion protection ability of formed passive film on the alloy's surface over time.Specifically,FSPed region exhibited superior passive behavior and uniform corrosion resistance compared to base metal.This improvement was attributed to a more homogeneous microstructure of stir zone,which hindered micro-galvanic coupling effect.However,it was observed that FSP-treatment did not effectively impede the propagation of pitting corrosion.
