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

摘要:

本文主要研究了激光选区熔化成形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)三种热处理后显微组织结构的转变与力学性能之间的关系。实验结果表明,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 ℃×1480 bar/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、抗拉强度和硬度显著提高,分别达到1191 MPa、1361 MPa、490(HV0.2),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,获得良好的综合力学性能。

Abstract:

This paper studies for the effect of solution-aging (SA), homogenization + solution aging (H+SA), Hot isostatic pressing + solution-aging (HIP + SA) three different heat treatments 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 phase precipitating among the interdendritic region. The δ phase was prone to precipitate when treated by proper homogenization, but the material can not be strengthened without γ"and γ " phases. Hot isostatic pressing(1080 ℃×1480 bar/2 h) can considerably removed Laves phase 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 of γ "、γ " phase, so HIP+SA treatment significantly increases the strength of Inconel 718 alloy, the mechanical properties of Inconel 718 alloy reached their optimum combination at UTS=1361 MPa, 0.2% YS=1191 Mpa, and HV0.2 =490, and the elongation after breaking is 13.30%.