近β型钛合金Ti-B19时效过程中的相变及显微组织

Phase Transformation and Microstructure Evolution in Near β Ti-B19 Titanium Alloy During Aging Treatment

研究了Ti-B19台金300℃～750℃时效过程中的相变和显微组织演变=结果发现：300℃～350℃时效过程中，在芦基体上首先会形成球状ω相，α相必须借助中间过渡相ω形核．多呈颗粒状；400℃—450℃时效．α相既可通过中间ω相转变．多星颗粒状，也可直接从口相中形桉，多呈针状；500℃～650℃时效，针状α直接从β晶界或晶内析出，500℃以匕时效可发现点状口相“连点成绩”的现象．可能与变形带有关；700℃～750℃时效．平衡α相多呈棒状。700℃时效10min发现块状α相析出。试验温度范围内大多数α相与卢基体满足Burgers位向关系，但在400℃～500℃时效10h左右有不符合Burgers位向关系的2α相出现。

The phase transformation and microstructure evolution of near β titanium alloy Ti-B 19 during solution treatment and aging treatment has been studied systematically using OM, SEM and TEM. The results showed that Ti-B19 solution treated at 900℃ for 1 h, air cooled, presented an equiaxed β structure consisting of metastable β phase and silicide phase. When the specimens were aged between 300℃ and 350℃, the globular ω phase formed firstly in β matrix, and then gradually transformed to equilibrium particle a phase with prolonging of aging time, with increasing the aging temperature to 400℃-450℃, acicular a could precipitate directly from metastable β phase besides particle a precipitation from β phase through transition of ω phase which is similar to that of 300℃ to 350℃. Upon increasing the aging temperature to 500℃-650℃, acicular α phase precipitated directly in β grains or along β grain boundaries. Linea a phase consisting of particle a phase was found at the ageing temperature above 500℃. Aging at 700℃ to 750℃, rod-like a phase precipitated along βgrain boundaries or in β grains because of lower rate of nucleation and rapid rate of growth of a phase. Bulk-like a was found when aged at 700℃ for 10 min. Usually, most of a phase precipitated from β phases obeyed the Burger＇s orientation relationship, however, some non-burger＇s a phase, e. g. 2α phase was observed in the specimens aged at 400℃-500℃ for about 10 hours.