The effect of laser welding on the microstructure and mechanical properties of TA15 alloy formed by SLM
TA 15 alloy was prepared by laser selective melting forming process,and the effect of laser welding on the microstructure and mechanical properties of TA 15 alloy was studied.The results indicate that the microstruc-ture of TA 15 alloy formed by SLM is needle shaped α'-martensite distributed in a basket like pattern.After weld-ing,the microstructure of the welded joint is also dominated by α'-martensite,but the size increases and transforms into flakes.At the same time,a certain amount of Widmannstatten structure was formed at the welding joint posi-tion.After welding,the SLM formed TA 15 alloy exhibits a decrease in room temperature and 500 ℃ tensile proper-ties compared to the base material,due to the formation of large-sized α'-martensite and unfavorable Widmannstat-ten structure.The room temperature tensile strength decreases by about 4.7％to 6.1％,the room temperature yield strength decreases by about 8.9％to 10.2％,the room temperature elongation decreases by about 25.5％;the high temperature tensile strength decreases by about 8.4％to 13.6％,the high temperature tensile strength decreases by about 7.2％to 10.3％,and the high temperature elongation decreases by about 12％.The transverse and longitudi-nal tensile fracture morphology of the base material are composed of numerous small and uniform ductile dimples,exhibiting characteristics of ductile fracture.Due to the formation of pores during welding,some of the welded joints exhibit circular holes with regular shape and smooth bottom on the tensile fracture.The appearance of pores leads to a significant decrease in plasticity,with the maximum reduction in elongation at room temperature and 500 ℃ being about 41％to 44％.
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