长期热老化对铸造奥氏体不锈钢组织和性能的影响

EFFECT OF LONG TERM AGING ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF CAST AUSTENITIC STAINLESS STEELS

将铸造奥氏体不锈钢在400℃下时效至10-4h,通过力学性能测试和组织观察,分析了老化时间对力学性能和组织结构的影响.结果表明：铁素体相的体积分数随老化时间没有变化;长期老化后材料的磁导率降低,同时铁素体相的纳米压入硬度增加;材料的Charpy冲击功随老化时间迅速下降,冲击断口形貌也随之不断变化;通过TEM观察发现,铁素体相在长期老化后析出了弥散的α′相和少量的G相,α′相是由铁素体发生调幅分解而生成的,是导致铸造奥氏体不锈钢热老化脆化的主要原因.

In order to study the mechanism of mid-temperature thermal aging embrittlement in cast austenite stainless steel（CASS）,the mechanical properties and microstructure were investigated of CASS which was aged at 400℃for 10-4 h.The results show that,no change in the ferrite content （volume fraction） was detected.After long term aging,the magnetic permeability of the CASS declined, but the nano-hardness of ferrite phases increased.The Charpy impact energy decreased rapidly and the impact fracture morphologies changed with aging time.Large number ofα＇ particles precipitated homogeneously in the ferrite phases of the CASS aged for 10~4 h.α＇ precipitation produced by spinodal decomposition in ferrite was considered to the primary mechanism of thermal aging in CASS at mid-temperature. G phases were also observed in some positions of ferrite after long term aging.