TC4钛合金电子束焊接接头相变的热力学特征

阐明了TC4钛合金电子束焊接接头相变的热力学特征,从热力学角度分析了TC4钛合金电子束焊接接头在不同的热处理条件下形成不同组织结构的机制,为通过改变热处理制度控制TC4钛合金电子束焊接接头相变的方法,提供了理论基础.结果表明,TC4钛合金电子束焊接接头的相变驱动力来源于新相马氏体和母相的化学自由能差,形成的马氏体贯穿整个晶粒,并且其取向呈一定的角度;低于MS点的焊后热处理只能使马氏体长大,而高于MS点的焊后热处理不仅使马氏体长大,还使部分β相成为饱和固熔体,并残留在马氏体片层之间.

Thermodynamic character of phase transformation of TC4 titanium alloy electron beam welded joint

The thermodynamic character of phase transformation of TC4 titanium alloy electron beam welded joint was described.In the point of thermodynamic view,the formation mechanism of different microstructures of TC4 titanium alloy joints in the different heat treatment conditions was analyzed,which provides theoretic base for the method to control phase transformation of TC4 titanium alloy electron beam welded joint by changing heat treatment conditions.The driving force of phase transformation of TC4 titanium alloy electron beam welded joint comes from the difference of chemical free energy between the new phase martensite and the parent phase.The martensite forms throughout the grain,and its orientation was a certain angle.In the case of the post-weld heat treatment which temperature is lower than M_s points,martensite only grows up,but in the case of the post-weld heat treatment which temperature is higher than M_s point,not only martensite grows,but also part of the β-phase becomes saturated solid solution and leaves among the martensite film layers.