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Zhang J.,General Iron and Steal Research Institute | Liang X.,General Iron and Steal Research Institute | Cheng Y.,General Iron and Steal Research Institute | Zeng W.,Northwestern Polytechnical University | Xue Q.,Aviation Industry Corporation of China
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2014

The microstructure evolution and mechanical property of Ti-22Al-25Nb (at%) alloy after near-β isothermal forging and heat treatment were studied. The results indicate that the duplex microstructure, which is consisted of a small amount of equiaxed α2 particles and B2 matrix (containing fine lath O) appears after near-β isothermal forging and then air cooling. And this kind of duplex microstructure still exists after 960°C solution treatment with water cooling and then aging. However, when the alloy is treated at 940°C followed by water cooling and then aged, the tri-morphology microstructure, which is consisted of a small amount of equiaxed α2 particles, coarse and fine lath O and B2 matrix, occurs. The strength of the alloy is reduced owing to the coarse lath O, while the ductility, endurance, fracture toughness and fatigue behavior are all improved which is of better matching than the duplex microstructure.


Zhang J.,General Iron and Steal Research Institute | Zhang H.,Fushun Special Steel Co Ltd | Zhang X.,Fushun Special Steel Co Ltd | Liang X.,General Iron and Steal Research Institute | And 2 more authors.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2010

The detailed microstructure characteristics and the formation regulation of the duplex microstructure of Ti-23Al-17Nb (at%) alloys under different heat treatment conditions were studied. The effects of detailed microstructure characteristics on the mechanical properties of alloys were also investigated. The approaches to improve the both tensile and endurance properties at elevated temperature were discussed. The results indicate that for the alloys forged in (α2+B2) phase field, the duplex microstructure can be obtained either by treatment of solution in (α2+B2) field and oil quenching plus aging in (α2+B2+O) field. The volume fraction, size and distribution pattern of O phase laths can be controlled well. The relatively lower aging temperature is of benefit to form the finer and more random distribution of O phase laths. Increasing the volume fractions of O phase laths can improve the endurance properties at elevated temperature but decrease the room-temperature elongation in the case of similar sizes and same percent content (15%-20%) as equiaxed α2 particles, while the finer sizes of O phase laths can increase the tensile properties both at room and elevated temperatures, but decrease the endurance properties. The optimum matching of tensile strength, elongation and endurance properties of the alloys at elevated temperature can be obtained by the heat treatment of 1060°C solution and oil quenching plus 850°C aging.

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