去应力退火SLM成形Inconel 738合金组织和性能演变

Evolution of Microstructure and Properties of SLM Formed Inconel 738 Alloy during Stress Relief Annealing

摘要:

由于选区激光熔化(SLM) 制备Inconel 738合金过程中快速熔化凝固的特点，成形合金中存在较高的残余应力，影响合金的服役。本文主要研究了不同退火温度 (700 ~900 ℃)下保温24 h后合金中残余应力、析出相行为、组织和性能演变。结果表明：退火过程中，组织演变机制为静态回复，发生位错迁移和晶界类型转变；形成的短棒状γ"相(240~440 nm)和球状γ"相(50~250 nm)；晶界碳化物分布由点状向连续状转变，类型由MC向M23C6转变；800 ℃退火后，残余应力由380.94 MPa(沉积态)下降至-66.7 MPa，残余应力得到释放；随着退火温度升高，硬度和抗拉强度先增大后减小，延伸率先减小后增加，800 ℃退火后，合金具有最高的硬度、抗拉强度 (581.2 HV、1330 MPa)为铸造性能(410 HV、945 MPa)的1.42倍、1.41倍。

Abstract:

Due to the characteristics of rapid melting and solidification in the process of preparing Inconel 738 alloy by selective laser melting (SLM), there is residual stress in alloy, so alloy cannot be directly used. Stress relief annealing is required. The evolution of residual stress, precipitation behavior, microstructure and properties in the alloy was mainly studied after annealing at different temperatures (700~900 ℃) for 24 h. The results show that the microstructure evolution mechanism is recovery，dislocation migration and rearrangement and grain boundary style changes were occured，a bimodal distribution of spherical γ "phase (50~250 nm) and short rod-shaped γ" phase (240~440 nm) are formed，the grain boundary carbides change from point to continuous and the type of carbides changed from MC to M23C6; After annealing at 800 ℃, the residual stress decreased from 380.94 MPa (AS-SLMed) to -66.7 MPa, and the residual stress was eliminated; With the annealing temperature increased, the microhardness and tensile strength first increased and then decreases, and the elongation decreases first and then increases. The alloy has the highest microhardness and tensile strength (581.2 HV, 1330 MPa) which are 1.42 times and 1.41 times of the properties of casting (410 HV, 945 MPa) after annealing at 800 ℃.