内燃机用Ti-42.5Al-4Nb-1Mo-0.2B合金高温组织研究

Study on High Temperature Microstructure of Ti-42.5Al-4Nb-1Mo-0.2B Alloy for Internal Combustion Engine

热处理可以有效细化Ti-Al合金晶粒,改善微观组织,提高性能。通过微观组织分析研究热处理温度对内燃机用Ti-42.5Al-4Nb-1Mo-0.2B合金组织的影响。结果表明:合金在铸态下主要为片层状组织形貌,合金组织中的B2相和γ相以混合状态存在。淬火组织内大块γ相已经全部消失,B2晶粒内只存在数量较少的细小棒状α2晶粒。在高温状态下合金组织内存在大量β相,温度越高越易发生动态再结晶。随变形温度的升高,合金γ相的数量明显减少,γ相开始析出α2相层片结构,生成α2/γ片层状组织,同时也有一部分γ相全部转化为α2相。

Heat treatment can effectively refine the grain size of TiAl alloy and improve the microstructure and properties of the alloy.The effect of heat treatment temperature on microstructure of Ti-42.5Al-4Nb-1Mo-0.2B alloy for internal combustion engine was studied by microstructure analysis.The results show that,the microstructure of the alloy is mainly lamellar in the cast state,and the B2 phase andγphase in the alloy structure exist in a mixed state.In the quenched microstructure,the bulkγphase has disappeared completely,and there are only a few fine rod-likeα2 grains in B2 grains.With the increase of deformation temperature,the number ofγphase decreases obviously.Theγphase begins to precipitateα2 phase lamellar structure,formingα2/γlamellar structure,and someγphases are transformed intoα2 phase.