| γ-TiA1 alloy has excellent high temperature strength, creep resistance, oxidation behavior and flame-retardant properties, with the deepening of research in recent years, Low room temperature plasticity become the main performance defects in the process of the alloy in practical, γ-Ti A1 alloy at room temperature mechanical properties are greatly influenced by the alloy microstructure, thereby obtaining fine and uniform microstructure is particularly important, in this paper, using the method of cyclic heat treatment, refining alloy layer of the organization, and then improve the alloy’s mechanical properties at room temperature.This paper mainly studied the heat treatment system on the new γ-TiΑl alloy TiAl-3Ta-x(W,Cr) the influence of microstructure refinement effect and mechanical properties at room temperature, mainly including the two following aspects of content: one, cyclic heat treatment methods are applied to refine the squeezed state TiAl-3Ta-x(W,Cr) alloy layer organization, optimization of heat treatment process parameters, obtain ideal fine fully lamellar microstructure, improve its tensile mechanical properties at room temperature; Second, the study without heat treatment the squeezed state TiAl-3Tax(W,Cr) alloy under 815℃, 870℃ and 925℃ high temperature oxidation behavior, by adding alloying elements Ta to improve its high temperature oxidation resistance, for the study of the alloy of cyclic heat treatment after different organizational state of high temperature oxidation behavior.TiΑl-3Ta-x(W,Cr) alloy first preprocessing in single phase area,cooling fully lamellar organization, high temperature heat treatment can eliminate the anisotropy of the squeezed state alloy, newly generated lamellar organization shape become such as shaft, finally it is concluded that 1300℃/5 min for alloy single phase zone, the optimal heat treatment system. The alloy in the α+γ two-phase orthogonal cyclic heat treatment experiment was carried out, under different heat treatment system(holding temperature T=1130~1190 ℃, holding time t=3~10 min, cycle number n=l~7), different types of microstructure can be obtained. Within the scope of the above parameters, the increase of temperature, the extension of time, with the increase of cycle number, refining alloy layer of organization. Short-time thermal cycle heat treatment process, the increasing number of cyclic heat treatment, can effectively destroy alloy organization genetic, makes the new α2/γ layer plate crystal grew up too late, to achieve the goal of refining lamella organization. The nucleation and growth of the new α2/γ fine lamellar microstructure mainly occur along the grain boundaries or intracrystalline nucleation, with grain boundary nucleation is given priority to, belong to the phase change recrystallization nucleation. Alloy by 1190 ℃ /10min/7 times/AC can gain the mostest tiny lamellar microstructure, the average layer of grain size can be up to 30 microns.Cyclic heat treatment can significantly improve the alloy at room temperature tensile properties, alloy after 1190 ℃ /10 min/7 times/AC tiny FL organization best room temperature tensile properties, the alloy at room temperature tensile strength of 409.61 MPa, the elongation of the delta is 2.81%. Within the scope of the heat treatment parameters, with the increase of the cycle temperature rise, cycle times, heat preservation time, decrease of tensile strength, elongation at room temperature significantly higher delta, room temperature plasticity of improvement.TiΑl-3Ta- x(W,Cr) alloy at 815℃, 870℃ and 925℃ under the oxidation behavior of studies show that adding elements Ta, can make the high temperature oxidation resistance of alloy has certain improvement, inside the oxide layer is the most close to the metal substrate to form a kind of TiO2 and AlTaO4 distribution of mixed oxide layer, and oxide layer of AlTaO4 can effectively control the oxidation rate, so as to achieve antioxidant effect. |
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