热处理工艺对SLM成形汽车用Fe-35Mn铁基高锰合金组织与力学性能的影响

Effect of heat treatment process on microstructure and mechanical properties of SLM formed Fe-35Mn Fe based high manganese alloy for automobile

采用激光选区熔化(selective laser melting,SLM)成形技术制备汽车用Fe-35Mn铁基高锰合金,并分别采用固溶、时效以及固溶–时效3种不同的工艺进行热处理,分析和测试合金的显微组织与力学性能。结果表明:SLM成形态Fe-35Mn高锰合金经过固溶或固溶–时效处理后,晶粒细化,并生成许多孪晶。与固溶态合金相比,固溶−时效态合金的晶粒更大,晶粒中存在均匀分布的孪晶组织,并且孪晶尺寸更大。SLM成形态Fe-35Mn合金经过不同的热处理后,均生成α-Mn相。随拉伸应变提高,固溶态合金最早发生塑性变形,塑性最好;经过时效处理后,合金的抗拉强度与屈服强度提高,但冲击韧性与伸长率降低;经过固溶−时效处理后,合金的孔隙数量最少,冲击韧性与伸长率达到最大(分别为22.8 kV/J和21.6%),具有良好的塑性。SLM成形态及热处理态Fe-35Mn合金的拉伸断口均呈现韧窝断裂特征。固溶−时效态合金的拉伸断口孔隙数量最少,塑性最好。

The selective laser melting(SLM)was used to prepare Fe-35Mn Fe-based high Mn alloy for automobile.Three heat treatment processes,namely solid solution,aging,and solid solution-aging,were used to treat the alloy,and the microstructure and mechanical properties of the alloy were analyzed and tested.The results show that Fe-35Mn alloy prepared by SLM and treated by solid solution or solution-aging treatment can refine the grain and generate many twins.Compared with the alloy of solid solution treatment,larger size grains are formed after the solid solution aging treatment,and the twins size of solution aging alloy is larger than that of solution aging alloy.After different heat treatment,Fe-35Mn alloys all produceα-Mn phase.With the increase of tensile strain,the solution alloy has the earliest plastic deformation and the best plasticity.After aging treatment,the tensile strength and yield strength of high-Mn Fe-35Mn SLM alloy increase,but the impact toughness and elongation decrease.After solution aging treatment,the number of pores is the least,the impact toughness and elongation reach the maximum(22.8 kV/J and 21.6%,respectively),and the alloy has good plasticity.Both the morphology of SLM and the tensile fracture of heat-treated Fe-35mn alloy are dimple fracture.The solution aged alloy has the least number of pores and the best plasticity.