The Research On Reactive Sintering And Extrusion Of Ti/Al Composite Powder Prepared By Mechanical Milling

TiAl based alloys are widely studied because their light weight and excellent elevated temperature properties such as high strength retention, resistance to creep and oxidation. However, their application is currently limited by the poor ductility and strong resistance to deformation at elevated temperature. In addition, it is difficult to prepare TiAl alloy with fine and homogeneous microstructure by traditional casting and mechanical working processes. Therefore, a new technology, which consists of the mechanical milling (MM), reactive sintering and hot hydrostatic extrusion has been put forward.The material of the experiment is compact Ti/Al composite powders prepared by high energy ball milling. The compact Ti/Al composite needs reactive sintering at low temperature and high temperature, in order to get high densified TiAl alloy. And then hot hydrostatic extrusion is used to press the sintered billets. The following aspects have been researched on.Low temperature reactive sintering was studied. The expansion and dehiscence behavior during the vacuum reactive sintering below 660℃of compact Ti/Al composite powders was experimentally investigated, and the reasons of expansion and dehiscence were theoretically analyzed. The method of low temperature reactive sintering was generalized, and the experiment testified the method effective. The rule of the expansion of the billets was generalized from the result of density of the billets. At last, the regularity of generating intermetallic compound at low temperature of TiAl alloy can be obtained by X-Ray analysis of the obtained samples.The following aspects were accomplished after high temperature reactive sintering. The rule of the shrinkage of the billets was generalized from the result of density of the billets, which have been reactive sintering at high temperature. By X-Ray analysis of the obtained samples the degree of the reaction was researched when the time of ball milling changed. At last the regularity of the metallurgical structure of TiAl alloy was investigated, when the high temperature changed.The following aspects were accomplished after hot hydrostatic extrusion.