【摘要】 采用热模拟压缩试验研究了Ti-40阻燃钛合金在温度900℃～1100℃、应变速率0.01s-1～10s-1范围内的高温变形特性,发现合金的流动应力-应变曲线具有应力峰和流变软化特征,在高温、高应变速率下,出现不连续屈服现象。根据动态材料模型(DMM)建立的Ti-40合金加工图大致可以分为5个区域:(1)在温度900℃～950℃,应变速率大于1s-1时,易发生45o角剪切开裂,出现明显的剪切变形带,功率耗散率达最小值。(2)在温度1000℃～1100℃、应变速率大于1s-1时,易出现“豆腐渣”式和纵向开裂,大变形时出现局部塑性流动。这2个区域为流动失稳区,在制定热加工工艺时应尽量避免。(3)在高温(≥1050℃)、低应变速率区(≤0.1s-1),功率耗散率为46%～76%,达到最大值,呈现连续再结晶的特征。(4)在900℃～950℃、应变速率0.01s-1～0.1s-1区域内主要发生动态回复,功率耗散率为22%～32%。(5)在温度950℃～1050℃、应变速率0.1s-1～1s-1范围为再结晶区域,功率耗散率为36%～50%。结果表明,加工图是控制材料组织演变和优化工艺的一种有效手段。更多还原

【Abstract】 The hot deformation characteristics of Ti-40 burn resistant titanium alloy were studied in the temperature range of 900℃~1100℃ and strain rate range of 0.01 s-1~10 s-1 using hot compression tests. The stress-strain curves exhibited an obvious peak followed by a broad flow softening. Discontinuous yielding occurred during deformation in higher temperature and higher strain rate ranges. The processing maps developed on the basis of dynamic material model (DMM) exhibited the following five domains. (1) The alloy exhibited a domain of recrystallization in the temperature range of 950℃~1050℃ and strain rate range of 0.1 s-1~1 s-1 with a power dissipation efficiency of about 36%~50%. The microstructure showed a mixed grain structure containing large prior β grains and small recrystallized grains. (2) The second domain, which had a peak efficiency of 46%~76%, occured at higher temperature (≥1050℃) and lower strain rate (≤0.1 s-1). Microstructural observations revealed that this domain represented continuous recrystallization. (3) This alloy underwent dynamic recovery in the temperature and strain rate regime from 900℃ to 950℃ and from 0.01 s-1to 0.1 s-1. (4) Adiabatic shear band and shear cracking occurred at 900℃to 950℃ and a strain rate was greater than 1 s-1. (5) This alloy exhibited “bean-curd-refuse like” cracking or longitudinal cracking due to oxidation of element V at 1000℃ to 1100℃ and a strain rate was greater than 1 s-1. It is proved that processing map is an effective method for successful forging and microstructural control.更多还原