时效温度对马氏体不锈钢激光焊接接头组织和性能的影响

对Fe-Cr-Ni-Mo-Ti型(0Cr13Ni7MoTi)马氏体时效不锈钢激光焊接接头进行不同温度时效处理,时效温度选择在420～580℃范围内。激光焊接接头显微组织呈现出焊缝区、热影响区(Heat affected zone,HAZ)和基体三个不同区域。结果显示,在500℃以下时效处理,焊缝区、热影响区和基体主要由马氏体板条组成,在540℃及以上温度进行时效处理,三个区域均有逆转变奥氏体形成,使各区域硬度下降;焊接接头经过时效处理后各个区域的硬度变化规律不一致,时效后硬度低点出现于热影响区或基体;拉伸测试显示,不同时效态的断裂位置均与硬度低点区域一致,屈服强度在460℃时效时取得最大值,此温度时效处理的焊接接头具有最佳的拉伸性能;拉伸断口断裂机制发生由未时效的准解理断裂到时效态的韧性断裂转变。

Microstructure and Mechanical Properties of Stainless Maraging Steel Laser Weldments after Aging at Different Temperatures

The Fe-Cr-Ni-Mo-Ti(0Cr13Ni7MoTi)stainless maraging steel laser weldments have been investigated after post-weld ageing at different temperatures.The post-weld ageing treatments are performed in a temperature range of 420 ℃ to 580 ℃.Metallographic characterization of laser weldment reveals three zones,i.e.fusion zone,heat affected zone(HAZ) and unaffected parent material zone.Martensite is the predominant phase in the three zones when the ageing temperature is lower than 500 ℃,and large amount of reverted austenite occur in the three zones on ageing at above 540 ℃,this lead to hardness decrease in fusion zone and HAZ.After aging treatments,the hardness in three regions varies in different ways,low hardness appears in the HAZ or unaffected parent material zone.The tensile tests reveal that fracture location occurred in low hardness region and tensile properties are optimum after ageing at 460 ℃.Tensile fracture mechanism changes from brittle fracture to the ductile fracture under given aging treatments conditions.