Microstructure in Weld Heat-affected Zone of Beta Titanium Alloy(Materials, Metallugy & Weldability)

概要

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Relation between microstructure and hardness of β titanium Ti-15V-3Cr-3Sn-3Al alloy and its welds was investigated by means of transmission electron microscopy and X-ray diffraction technique. As the aged Ti-15V-3Cr-3Sn-3Al alloy was welded by using DCSP-TIG welding procedure, the decrease of the hardness occurs in the heat-affected zone, because of the solution of a phase. The hardness in the weld heat-affected zone is considerably higher than that of the base metal, as the welded sample was aged at 773K after welding. This phenomena was mainly due to the increase of the precipitation amounts of fine α phase. Maximum hardness after aging treatment increases with increasing solution treatment temperature. The precipitation of α phase occurs, as the specimens were aged at 573K, 673K and 773K after solution treatment. The precipitation amount of α phase increases with increasing solution temperature. The increase of the solution treatment temperature also causes the decrease of the lattice parameter α c_0 during aging by X-ray diffraction technique, and causes homogeneous precipitation and fine precipitation of α phase during aging by means of transmission electron microscopy.
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