Microstructure and room temperature tensile property of as-cast Ti44Al6Nb1.0Cr2.0V alloy
(School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
Abstract: The nominal Ti44Al6Nb1.0Cr2.0V alloy was newly designed and prepared by vacuum consumable melting technique with the ingot sizes of d225 mm×320 mm. The results show that the average lamella colony size is 780-1830 μm. This as-cast alloy has a modified near lamellar (M-NL) structure that is composed of mainly larger (α2+γ) lamella colonies and smaller (B2+equiaxed γ) blocky morphology. It exhibits the moderate tensile properties at room temperature, in which the Region (5) yields the ultimate tensile strength (UTS) about 499 MPa and the elongation about 0.53%. The obvious brittle fracture characteristics and trans-granular interlamellar fracture are the predominant modes. After room temperature tensile testing, there are some <101] and a few 1/2<112] superdislocations in the γ phase. The as-cast microcrack is the main factor to deteriorate the tensile property, which results in the premature fracture, poor ductility and few dislocations. The addition of Nb, Cr and V can decrease stacking fault energy (SFE) obviously, which is helpful to enhancing the ductility of the alloy.
Key words: titanium aluminum alloy; as-cast; microstructure; tensile property; microcrack