Development of technology for production and heat treatment of powder titanium Ti6,1Al5,4V1,8Sn alloy

Information on the production technology of powder titanium Ti6,1Al5,4V1,8Sn alloy, as well as results on the effect of heat treatment on its the structure, phase composition and properties are presented. It is shown that for powder product it is possible to recommend the heating temperature of the workpieces 900...950 °C, heating of the stamp to 850...900 °C with the elongation coefficient μ l 9. Increase in the extrusion temperature of the workpiece above 950 °С does not give significant increase in density and, at low elongation coefficient, leads to grain growth of the metal structure. The effect of quenching and melting temperatures on the decomposition of α′-martensite, precipitation of the α2-phase Ti3Al and, in particular, during quenching of alloy specimens from the β-region, as well as in the case of quenching from (α + β)-state is studied.

A New Mechanism of Dynamic Phase Transformations in An Isothermal Forged Beta–Gamma Intermetallic Alloy

A new mechanism of dynamic phase transformations of α2 ↔ γ in an isothermally forged γ-TiAl-based alloy that occur simultaneously during a short-term exposure at 1000 °C is identified in this study. In the heating process, γ phase significantly decreases through a phase transformation of γ → α2, while new γ lamellae are precipitated in the interior of equiaxed grains of α2 phase through a phase transformation of α2 → γ. The reasons for the presence of these two inverse phase transformations α2 ↔ γ occurring simultaneously are discussed.

Effect of Heat Treatment on the Microstructure and Properties of a Ti3Al Linear Friction Welding Joint

Heat treatment at different temperatures was carried out on a Ti3Al linear friction welding joint. The characteristics and evolution of the microstructure in the weld zone (WZ) and the thermo-mechanically affected zone (TMAZ) of the Ti3Al LFW joint were analyzed. Combined with the heat treatment after welding, the effect of the heat treatment temperature on the joint was discussed. The test results indicated that the linear friction welding (LFW) process can accomplish a reliable connection between Ti3Al alloys and the joint can avoid defects such as microcracks and voids. The weld zone of the as-welded Ti3Al alloy joint was mainly composed of metastable β phase, while the TMAZ was mainly composed of deformed α2 phase and metastable β phase. After being heat treated at different temperatures, the WZ of the Ti3Al LFW joint exhibited a significantly different microstructure. After heat treatment at 700 °C, dot-like structures precipitated and the joint microhardness increased significantly. Subsequently, the joint microhardness decreases with the increase in temperature. Under heat treatment at temperatures above 850 °C, the formed structure was acicular α2 phase and the joint microhardness after heat treatment was lower than that of the as-welded joint.