Microstructure Control for Attaining Over 2Gpa of Tensile Strength in Beta Titanium Alloys

贝塔钛合金的特点包括在固溶处理状态下具有优异的冷成形能力，以及在随后的时效处理后强度增加。因此，冷成形后的时效方法是一种利用贝塔钛合金的特点的热处理方法。冷加工后时效的热处理方法显著促进了工业β钛合金的时效响应和α相的细小析出。据报道，与固溶处理后不进行冷加工的时效方法相比，这种热处理方法改善了商业贝塔钛合金Ti-13-11Cr-3Al的强塑性平衡，但人们认为这种热处理方法在追求高强度的同时降低了塑性，并且无法改善商业贝塔钛合金Ti-15V-3CR-3SN-3Al的强塑性平衡。对冷锻造后双重时效的Ti-15V-3CR-3SN-3Al合金进行了拉伸试验，即高温时效和低温再时效。823K、873K和923K短时时效和673K再时效的组合大大改善了该合金的强塑性平衡，实现了高强度和足够的拉伸伸长率。这种双重时效工艺进一步减小了冷锻压缩量对时效后力学性能的影响。

The features of the beta titanium alloy Include Its superior cold-formability in the solution-treated state and Its Increased strength after undergoing subsequent aging-treatment. Consequently, the method of aging after cold-forming Is a heat-treatment method which utilizes the features of the beta titanium alloy. The heat-treatment method of aging after cold-working is known to remarkably promote the aging response and fine precipitation of alpha phase in commercial beta titanium alloy. It was reported that, compared with the method of aging without cold-working after solution-treatment, this heat-treatment method Improved the balance between strength and ductility of commercial beta titanium alloy Ti-, 13-llCr-3Al, however, It was considered, - that this heat treatment method reduced ductility while aiming to achieve high strength and that the strength-ductility balance could not be Improved for commercial beta titanium alloy Ti-15V-3Cr-3Sn-3Al. Mechanical properties were studied by tensile test of Ti-15V-3Cr-3Sn-3AI alloy obtained by duplex-aging after cold-swaging, i. e. aging at high temperatures followed by re-aging at a lower temperature. Combinations of short-time aging at 823K, 873K and 923K and re-aging at 673K have greatly Improved the strength-ductility balance of this alloy, realizing high strength with adequate tensile elongation. This duplex-aging process further diminishes the Influence of reduction of cold-swaging on the mechanical properties after aging.