热处理对NiW中/重合金组织与性能的影响

Effect of heat treatment on the microstructural evolution and mechanical properties of NiW medium/heavy alloys

摘要:

本文研究了不同热处理温度对冷轧态Ni42W10Co1Mo合金微观组织及力学性能的影响规律。结果表明,随着热处理温度的升高,合金中TCP相由σ相向μ相转变,μ相再向σ相转变,基体组织由条带状变形组织逐渐转变为均匀的等轴晶。经900℃热处理,析出相主要以针状与块状μ相析出为主,同时还有少量颗粒状μ相,发生明显再结晶现象。经1200℃热处理,颗粒状σ相大量析出,基体组织完成静态再结晶过程。TCP相的析出消耗了基体中固溶强化元素W,导致合金的室温屈服强度下降,屈服强度由初始态合金的1564MPa下降至1200℃热处理后的479MPa。小尺寸的σ相能阻碍裂纹的扩展,有利于提升合金的塑性,经1200℃热处理合金延伸率达到了72.4%。然而较大尺寸的μ相对合金的塑性产生不利影响,经900℃热处理后合金延伸率仅有7.1%。

Abstract:

The influence of various heat treatment temperatures on the microstructural evolution and mechanical properties of the cold-rolled Ni42W10Co1Mo alloy was studied. The results indicated that the TCP phases transformed from σ phase to μ phase with the increase of heat treatment temperatures, and then transformed from μ phase to σ phase finnaly. The microstructure evolved from deformed dendrites to a uniform equiaxed grains. After heat treatment at 900°C, the precipitation phases are predominantly needle-like and blocky μ phases, with a small quantity of granular μ phases. Recrystallization was also evident. After heat treatment at 1200°C, a substantial amount of granular σ phases precipitated accompanying the completion of recrystallization. The extensive precipitation of TCP phases consumed a large amount of W element leading to a decrease of solid solution strengthening. The room temperature yield strength was decreased from 1564 MPa to 479 MPa after heat treatment at 1200°C, while, the elongation was enhanced to 72.4%. The precipitation of larger-sized μ phases was adversely to ductility, in contrast to the smaller-sized σ phases impeded crack propagation and enhcaned the ductility.