热处理对SLM成形15-5PH不锈钢组织和力学性能的影响

Effect of heat treatment on microstructure and mechanical properties of 15-5PH stainless steel by selective laser melting

分别对激光选区熔化(SLM)成形的15-5PH不锈钢试样进行620℃×4 h时效处理和1030℃×1 h固溶+550℃×4 h时效处理,比较不同状态SLM成形15-5PH不锈钢试样的微观组织及力学性能。结果表明,相对于SLM成形态试样,当不同热处理试样抗拉强度相当时,时效态试样显微组织主要为细小的树枝状晶粒,为马氏体、片状珠光体和铁素体的混合组织;固溶+时效态试样的显微组织主要由回火马氏体+铁素体+部分逆转变奥氏体组成,晶粒内部的树枝状结构基本消失,晶粒长大。与时效态相比,固溶+时效态试样的屈服强度、屈强比分别提高了33%、32%;冲击吸收能量、断后伸长率及断面收缩率分别降低了72.0%、35.5%、18.7%。

15-5PH stainless steel specimens were prepared by selective laser melting(SLM)forming process and then were aged at 620 C for 4 h,and solution treated at 1030 C for 1 h plus aged at 550℃for 4 h,respectively.The microstructure and mechanical properties of the 15-5PH stainless steel specimens formed by SLM under diferent states were compared.The results show that compared to SLMed specimen,when the tensile strength of the specimens obtained by different heat treatments is equivalent,the microstructure of the aged specimen is mainly composed of fine dendritic grains which is mix structure of martensite,lamellar pearlite and ferrite,while the microstructure of the solution treated+aged specimen is mainly composed of tempered martensite+acicular ferrite+partial reversed austenite.The dendritic structure inside the grains almost disappears and the grains grow.Compared with the aged specimen,the yield strength and yield ratio of the solution treated+aged specimens are increased by 33%and 32%,respectively,and the impact absorbed energy,elongation after fracture,and the percentage reduction of area are decreased by 72.0%,35.5%and 18.7%,respectively.