热处理对激光选区熔化成形Inconel 718合金显微组织结构和力学性能的影响

Effect of Heat Treatment on Microstructure and Mechanical Properties of Inconel 718 Alloy Fabricated by Selective Laser Melting

主要研究了激光选区熔化(selective laser melting,SLM)成形Inconel 718合金经固溶时效(SA)、均匀化+固溶时效(H+SA)、热等静压+固溶时效(HIP+SA)3种热处理后显微组织结构的转变与力学性能之间的关系。结果表明,沉积态试样的晶粒内部存在大量树枝晶结构,枝晶间析出了大量硬脆Laves相。恰当的均匀化处理虽能促进δ相析出,但无γ"、γ'相,材料强度较低。热等静压(1080℃,148 MPa,2 h)能有效消除沉积态中的Laves相和微孔,经随后SA处理,材料的晶粒明显细化,晶界趋于平直,且强化相析出,材料的屈服强度、抗拉强度和硬度(HV0.2)显著提高,分别达到1191 MPa、1361 MPa、4900 MPa,断后伸长率达13.30%,在提高材料强度的同时较大程度保留了材料的延展性,获得了良好的综合力学性能。

The effect of three different heat treatments,solution-aging(SA),homogenization+solution-aging(H+SA),and hot isostatic pressing+solution-aging(HIP+SA),on the microstructure and mechanical properties of selective laser melting(SLM)formed Inconel 718 alloy.The as-built Inconel 718 has a large number of dendritic structures,and there are many brittle laves phases precipitating among the interdendritic region.Theδphase is prone to precipitate when the alloy is treated by proper homogenization,but the material can not be strengthened withoutγ"andγ'phases.Hot isostatic pressing(1080℃,148 MPa,2 h)can considerably remove laves phases and micro pores of the as-fabricated samples,and combine with the solution aging treatment subsequently.It’s conductive to refine the grain size of the as-built samples,flat the grain boundaries,and promote the precipitation ofγ"andγ'phases,so HIP+SA treatment significantly increases the strength of Inconel 718 alloy.The mechanical properties of Inconel 718 alloy reach the optimum combination at UTS=1361 MPa,0.2%YS=1191 MPa,and HV0.2=4900 MPa,and the elongation after breaking is 13.30%.