Effects of Composition on Structure & Mechanical Property of TiAl Based Intermetallic Compounds

Abstract

The effects of Al content and ternary additions such as Mo, V and Si in as cast g based alloys made by plasma arc melting on solidification structures and mechanical properties were studied. The Columnar g /a₂ lamellar structures in Al-lean alloys due to primary a solidification had higher room temperature fracture strength and strain than g phase structures through the reaction of L + a = g in Al-rich alloys. The fraction of α₂ phase was found to decrease with increasing Al content in binary alloys. Fractography revealed that fine translamellar fracture is a man fracture mode in Ti-48 at.% Al alloy which led to a high fracture with more than 5%. The RT fracture strain was improved by the addition of 1.5 at.% Mo and 1 at.% Si. The mechanical propertied have been discussed in term of changes in unit cell volume and axial ration. In the case of Si, tensile properties coincided well with the change of axial ratio c/a. The strength and strain could be raised slightly to compare with binary system. The standard deviation has been low in lattice constant so deviation of c/a is 0.43% which is good one to help to analyze the strain in TiAl-X alloys. The first factor is c/a which means atomic anisotropy then is c*a² which is unit atomic volume of γ phase. The decreasing c/a is to decrease the atomic anisotropy and increase the materials atomic ductility in TiAl-X alloys.