Abstract The rolled Ti–15V–3Cr–3Sn–3Al (Ti-15-3) alloy plates were processed by friction stir processing (FSP) using an ultra-low heat input parameter of 100 rpm- 100 mm/min and 1.6 μm grain-sized microstructure was obtained. Subsequently, tensile tests were conducted in this microstructure within the temperature range of 625–725 °C with an interval of 25 °C at three different strain rates of 1 × 10−4 s−1, 3 × 10−4 s−1 and 1 × 10−3 s−1. The largest elongation of 842% was achieved at 675 °C and 3 × 10−4 s−1 and the present superplastic deformation is dominantly controlled by grain boundary sliding (GBS) accompanied by phase transformation and continuous dynamic recrystallization (CDRX). To the best of our knowledge, the elongation of 842% is the largest one for Ti-15-3 alloy at the temperature as low as 675 °C. The increasing temperature supplied more energy for GBS, which was beneficial to the achievement of excellent superplasticity. However, when the temperature increased over 675 °C, the α phase volume fraction severely decreased which led to the significant β grains growth, the high angle grain boundaries (HAGBs) remarkably reduced, all of which impeded the GBS hence the achievement of excellent superplasticity. Therefore, the largest elongation, most stable and uniform superplastic flow and lowest peak stress were achieved at the temperature of 675 °C for all the three testing strain rates of 1 × 10−4 s−1, 3 × 10−4 s−1 and 1 × 10−3 s−1.

中文翻译：

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搅拌摩擦加工细晶Ti-15V-3Cr-3Sn-3Al合金增强低温超塑性的最佳温度

摘要 轧制的 Ti-15V-3Cr-3Sn-3Al (Ti-15-3) 合金板采用搅拌摩擦加工 (FSP)，采用 100 rpm-100 mm/min 的超低热输入参数和 1.6 μm 晶粒获得了-尺寸的微观结构。随后，在 625–725 °C 的温度范围内以 25 °C 的间隔在 1 × 10-4 s-1、3 × 10-4 s-1 和 3 × 10-4 s-1 三种不同应变率下对该显微组织进行拉伸试验。 1 × 10−3 s−1。在 675 °C 和 3 × 10−4 s−1 下实现了 842% 的最大伸长率，目前的超塑性变形主要受晶界滑动（GBS）伴随相变和连续动态再结晶（CDRX）的控制。据我们所知，842% 的伸长率是 Ti-15-3 合金在低至 675 °C 的温度下最大的伸长率。升高的温度为GBS提供了更多的能量，有利于实现优异的超塑性。然而，当温度升高超过 675 °C 时，α 相体积分数急剧下降，导致 β 晶粒显着生长，大角度晶界（HAGBs）显着减少，所有这些都阻碍了 GBS 的实现，从而实现了优异的超塑性. 因此，对于 1 × 10−4 s−1、3 × 10−4 s−1 三个测试应变率，在 675 °C 温度下实现了最大的伸长率、最稳定和均匀的超塑性流动和最低的峰值应力。和 1 × 10−3 s−1。α相体积分数严重下降导致β晶粒显着生长，大角度晶界（HAGBs）显着减少，所有这些都阻碍了GBS获得优异的超塑性。因此，对于 1 × 10−4 s−1、3 × 10−4 s−1 三个测试应变率，在 675 °C 温度下实现了最大的伸长率、最稳定和均匀的超塑性流动和最低的峰值应力。和 1 × 10−3 s−1。α相体积分数严重下降导致β晶粒显着生长，大角度晶界（HAGBs）显着减少，所有这些都阻碍了GBS获得优异的超塑性。因此，对于 1 × 10−4 s−1、3 × 10−4 s−1 三个测试应变率，在 675 °C 温度下实现了最大的伸长率、最稳定和均匀的超塑性流动和最低的峰值应力。和 1 × 10−3 s−1。