Al/Ti扩散层形成的扩散溶解机制

分别在铝组元熔点之下和之上对Al/Ti镶嵌式扩散偶进行退火热处理,形成固-固和固-液扩散偶.利用光学显微镜、扫描电子显微镜和电子探针显微分析仪观察和分析Al/Ti固-固和固-液扩散层的形态和结构,并对其形成微观机理进行了研究.结果表明,Al/Ti固-固扩散层由一层TiAl₃构成;固-液扩散层由TiAl₃单相层与TiAl₃和Al(Ti)固溶体双相层两层构成,双相层TiAl₃和Al(Ti)固溶体的形态自铝向钛呈现规律性变化.Al/Ti固-固TiAl₃扩散层和固-液TiAl₃单相层的形成都是铝扩散溶解到钛中形成以钛为溶剂的Al-Ti固溶体结晶形成的;而Al/Ti固-液TiAl₃和Al(Ti)固溶体双相层是钛先溶解再扩散到液态铝中形成的Al-Ti液溶体结晶形成的.铝液中Ti原子浓度自铝向钛逐渐升高,导致了双相层TiAl₃和Al(Ti)固溶体形态的规律性变化.

Diffusion and dissolve mechanism of Al/Ti diffusion layer formation

Al/Ti diffusion couple made by inlaying was annealed under and above Al melting point, respectively, and solid-solid and solid-liquid diffusion couples were formed. the microstructure of Al/Ti solid-solid and solid-liquid diffusion layers were observed by OM and SEM-EDS, and the formation mechanism was investigated. The results show that Al/Ti solid-solid diffusion layer was composed by one layer of TiAl₃ But the solid-liquid diffusion layer was composed of single phase layer of TiAl₃ and dual-phase layer of TiAl₃+Al(Ti) solid solution. The formation of dual-phase layer changed regularly from Al to Ti. The Al/Ti solid-solid TiAl₃ diffusion layer and solid-liquid single-phase TiAl₃ layer were formed from diffusion of Al into Ti by forming AI-Ti solid solution with Ti as solvent. However, dual-phase layer TiAl₃+Al(Ti) solid solution formed by dissolving and spread of Ti to the liquid Al by forming Al-Ti liquid solution. It resulted in morphological variation of dual-phase layer TiAl₃+Al(Ti) solid solution that Ti atom concentration gradually increased in Al solution from Al to Ti.