分级球磨和真空热压烧结制备高铌TiAl合金的研究材料加工工程专业论文.docxVIP

哈尔滨工业大学工学硕士学位论文 哈尔滨工业大学工学硕士学位论文 - - II - Abstract TiA l-based alloys become a very potential high- temperature structural material because of its high specific strength, high specific stiffness and good high temperature performance. By now, the poor ability of room- temperature deformation and the weakness of high temperature oxidation resistance restrict the applications of TiA l-based alloys, the TiA l- based alloys containing high Nb show a much better general performance which earns people’s attention. By grading ball milling and vacuum hot-pressed sintered technology, high-Nb TiA l alloy were prepared. In order to improve the alloys high temperature performance and improve the alloys britt leness at room temperature, in this artical,high levels of Nb element(20at.%) are added, at first, grading ball milling is applied with elemental powders(TiA l high-energy ball milling+Nb- TiA l low-energy ball milling), and then milling powders are sintered with vacuum heating-press sintering process(low temperature reactive sintering+high temperature sintering), finally high N b containing TiAl alloys with ductile N b phase are prepared. T he main contents are as follows: The research of grading high- energy ball milling process is investigated. According to the rule for the impact of grind ing process on powers, Ti/Al composite powders are prepared by first-rank high energy ball milling, N b- TiAl compound powders are prepared by secondary low energy ball milling, Parameterschanges in behavior of milling process are studied, such as particle morphology size, grain, composition, thermal stability and so on.by observing the Photos of the morphology and analyzing the composition of powders, the change mechanism of particle morphology in milling process is defined; observed by TEM, microscopic change mechanis m in powders is verified ; by XRD and DTA analysis, the thermal stabilit y of milling powders is analyzed to provide the basis for the subsequent sintering process.throug