TC21合金低温时效过程中的马氏体分解机制

采用透射、X射线及显微硬度分析等方法,研究了TC21合金中淬火马氏体在长时间低温时效过程中的组织演变及马氏体分解机制。研究表明,淬火态TC21合金在400～450℃进行长时间等温处理后,易获得弥散分布的颗粒状α相,显著提高合金性能,而α相颗粒的形核与马氏体中层错的分布密切相关。正交马氏体在低温时效过程中的具体分解方式为α→α+α富→α+β亚稳→α+β。进一步提高时效温度或时效时间α相颗粒将粗化为片层状,降低合金强度。

Mechanism of martensite decomposition during low temperature ageing process for TC21 alloy

Microstructure evolution and martensite decomposition mechanism of quenched TC21 alloy during long term ageing process at low temperatures were studied by TEM,XRD and microhardness analysis techniques.Result shows that the alloys exhibit good properties after long term isothermal treatment at 400-450 ℃ due to α-phase particles uniformly distribute in the parent phase.Furthermore,TEM observation indicates that the nucleation of α-phase particle is related with the distribution of stacking faults in the quenched TC21 alloy.The transformation sequence of martensite decomposition for TC21 alloy is α→α+αrich→α+βmetastable→α+β.Further increasing the ageing temperature and time,α particles will coarsen to lamellar structure and strength of the alloy will decrease.The low temperature ageing porcess mentioned in this paper creates a new way to improve mechanical properties of TC21 alloy.