铸态阻燃钛合金的热加工图与变形机制研究

Hot Processing Map and Deformation Mechanism of as-Cast Burn Resistant Titanium Alloy

摘要:

在热模拟试验机上对铸态组织的阻燃钛合金（Ti-35V-15Cr-Si-C）进行了等温恒应变速率热压缩试验，温度范围为900~1200 ℃，应变速率范围为10-3~1 s-1，测试了其真应力-真应变曲线并对曲线上的应力σ突降进行了解释。基于动态材料模型建立了合金的热加工图，结合微观组织观察，确定了3个不同区域的高温变形机制：温度900~1030 ℃、应变速率小于0.1 s-1时，变形机制为动态回复和连续动态再结晶；温度大于1030 ℃、应变速率小于0.1 s-1时，功率耗散效率η出现峰值，除了动态回复和连续动态再结晶，还出现碳化物溶解现象；高应变速率（大致在0.01~1 s-1之间）区，是合金的变形失稳区域，较低温度时失稳机制为局部流动，高温失稳与碳化物溶解有关，=1 s-1时组织演变特征是项链状动态再结晶

Abstract:

Hot compressive deformation tests of as-cast burn resistant titanium alloy (Ti-35V-15Cr-Si-C) were performed on the Gleeble-1500 simulator in the temperature range of 900~1200 °C, over the range of strain rate from 10-3 s-1 to 1 s-1. The compressive true stress vs. true strain curves were measured. The discontinuous yielding phenomenon was explained. The hot processing maps developed on the basis of dynamic material model (DMM) exhibits the following three domains. The alloy dynamic recovery and continuous recrystallization in the temperature range from 900 °C to 1030 °C and at lower strain rate (＜0.1 s-1). A peak power dissipation efficiency area of 50%~65% occurring at higher temperature (≥1030 °C) and lower strain rate. In addition to dynamic recovery and continuous recrystallization, the carbide solution phenomenon is observed. The alloy exhibits a wide region of flow instability manifested by flow localization and carbide solution at higher strain rate. The ‘Necklace’ dynamic recrystallization occurs at the strain rate of 1 s-1