Solidification structures of high niobium containing TiAl alloys  

作　　者：JingwenXu JunpinLin YanliWang ZhiLin GuoliangChen 

机构地区：[1]StateKeyLaboratoryforAdvancedMetalsandMaterials,UniversityofScienceandTechnology,Beijing100083,China

出　　处：《Journal of University of Science and Technology Beijing》2005年第2期134-138,共5页北京科技大学学报（英文版）

基　　金：This research was sponsored by the State Key Project for Fundamental Research Developing Plan (No.G2000067206-2) and theNational Natural Science Foundation of China (No. 50274005).

摘　　要：To understand the effect of alloy stoichiometry on the microstructural development and mechanical behavior of γ-TiAl- based materials, it is necessary to have a determination of the phase relationships for the TiAl alloy system near the γ phase field. Cast structures and phases of Ti-(43-47)Al-8Nb-(1-2)Mn (at%) alloys have been studied by using scanning electron microscope and X-ray diffraction. Their solidification path and microstructure development during the solidification were analyzed. The experimental results show that the alloys with different Al contents form different macrostructures and microstructural morphologies. This indi- cates that the solidification paths are different with different Al contents. The alloy with 43Al forms equiaxed grain structure, and the solidification path is as follows: L —? L+β —? β —? α+β —> α+β cores —> O2+γ+B2 cores. Whereas the alloy with 47Al forms colum- nar grain structure, and the solidification path is as follows: L —> L+β —? α+β+L —? α+γ+β cores —> tXj+γ+BZ cores. The p phase is their primary solid phase and can be retained to ambient temperature. The alloy with 43Al solidifies completely into β phase. The peritectic reactions L+P —> α and L+α-? γ appear when the Al content increases to 47Al.To understand the effect of alloy stoichiometry on the microstructural development and mechanical behavior of γ-TiAl- based materials, it is necessary to have a determination of the phase relationships for the TiAl alloy system near the γ phase field. Cast structures and phases of Ti-(43-47)Al-8Nb-(1-2)Mn (at%) alloys have been studied by using scanning electron microscope and X-ray diffraction. Their solidification path and microstructure development during the solidification were analyzed. The experimental results show that the alloys with different Al contents form different macrostructures and microstructural morphologies. This indi- cates that the solidification paths are different with different Al contents. The alloy with 43Al forms equiaxed grain structure, and the solidification path is as follows: L —? L+β —? β —? α+β —> α+β cores —> O2+γ+B2 cores. Whereas the alloy with 47Al forms colum- nar grain structure, and the solidification path is as follows: L —> L+β —? α+β+L —? α+γ+β cores —> tXj+γ+BZ cores. The p phase is their primary solid phase and can be retained to ambient temperature. The alloy with 43Al solidifies completely into β phase. The peritectic reactions L+P —> α and L+α-? γ appear when the Al content increases to 47Al.

关 键 词：high niobium titanium aluminides MICROSTRUCTURE phase transformation β phase 

分 类 号：TG146.2[一般工业技术—材料科学与工程]