Microstructure and Formation Mechanism of Porous Ti-Al Intermetallics Prepared by Pressureless Sintering

摘要:

以Ti和Al 2种粉末为原料，采用粉末压制-无压烧结技术制备了TiAl多孔材料，并对其宏观形貌、相组成、孔结构、反应机制和孔隙形成机理进行了分析。结果表明：Ti-Al粉末压坯在烧结过程中发生了明显的体积膨胀，多孔材料的总孔隙率为49.88%~57.53%，开孔率为47.60%~56.15%。多孔材料主要由连续的颗粒骨架、骨架之间的大孔隙和骨架内部的小孔隙构成，孔隙主要来自粉末压坯颗粒之间存在的原始大孔隙、无压烧结过程中先熔化的Al颗粒在毛细作用下发生流动形成的原位大孔隙和析出过程在Ti-Al产物颗粒之间形成的小孔隙。Ti-Al多孔材料主要由TiAl3单相构成，无压烧结过程中Ti-Al之间发生了热爆反应。

Abstract:

Porous Ti-Al intermetallics materials were prepared form titanium and aluminum powders by pressureless sintering route, and the macro-morphology, phase composition, porosity, microstructure and formation mechanism of porous Ti-Al intermetallics were investigated. The results show that the volume expansion of the Ti-Al compacts is observed in all samples. The porosities of Ti-Al intermetallics are within the range of 49.88%~57.53%, and the open porosities are within the range of 47.60%~56.15%. The porous materials are made of interconnected skeleton, big pores among skeleton and small pores in the interior of skeleton. The interstitial pores in green powder compacts are the most important source of big pores of porous Ti-Al intermetallics, and the in-situ pores from the melting and flowing of aluminum powders is also significant to the formation of big pores. Small pores are from the precipitation of Ti-Al intermetallics particles in pressureless reactive sintering, and TiAl3 is the main phase of porous materials, and porous Ti-Al intermetallics are formed by thermal explosion mechanism.