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β锻造与热处理对粉末冶金TC4钛合金组织与力学性能的影响

Effect of β forging and heat treatment on microstructure and mechanical properties of powder metallurgy TC4 alloys

  • 摘要: 以氢化脱氢TC4钛合金粉末为原料,经冷等静压成形、真空无压烧结制备成TC4钛合金烧结坯。对TC4钛合金烧结坯进行β单相区锻造和固溶时效热处理,研究了β锻造与固溶时效热处理对粉末冶金TC4钛合金显微组织及力学性能的影响。结果表明:β锻造大幅减小了TC4钛合金烧结坯中的孔隙尺寸,显著提高了合金相对密度。锻造后合金的室温拉伸性能优异,抗拉强度达972 MPa,断后伸长率为16.0%。经固溶时效热处理后,TC4钛合金的强度和塑性均发生了显著变化,热处理后的合金强度较锻态提升超过200 MPa,但延伸率有所下降,从16.0%降低至8.2%。固溶时效对TC4钛合金的强化作用主要靠淬火基体中析出的次生α相强化。合金中残余孔隙尺寸的减小显著改善了烧结合金的疲劳性能,在最大应力480 MPa、应力比0.1的条件下,β锻造TC4钛合金循环周次达到7×106以上,固溶时效TC4钛合金循环周次达到107以上。

     

    Abstract: The TC4 titanium alloy powders prepared by hydrogenation-dehydrogenation (HDH) were used as the raw materials. The sintered TC4 titanium alloys were fabricated via cold isostatic pressing (CIP) followed by pressureless vacuum sintering. The TC4 sintered compacts were subjected to β single-phase region forging and subsequent solution-aging heat treatment. The effects of β forging and solution-aging heat treatment on the microstructure and mechanical properties of TC4 titanium alloys were investigated. The results show that the β forging drastically reduces the pore size inside the TC4 sintered compacts and remarkably increases the relative density of the alloys. The forged alloys exhibit the excellent room-temperature tensile properties with the ultimate tensile strength of 972 MPa and the elongation after fracture of 16.0%. After the solution and aging treatment, both the strength and the ductility of TC4 alloys change significantly. Compared with the forged alloys, the strength of heat-treated alloys increases by more than 200 MPa, while the elongation decreases from 16.0% to 8.2%. The strengthening effect induced by solution and aging treatment mainly originates from the precipitation of secondary α phases within the quenched matrix. The reduction in residual pore size greatly improves the fatigue properties of the sintered alloys. Under the maximum stress of 480 MPa and stress ratio of 0.1, the cycle fatigue life of β-forged TC4 alloys exceeds 7×106 cycles, and that of solution-aged TC4 alloys surpasses 107 cycles.

     

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