TC4钛合金电塑性压缩流变应力分析

FLOW STRESS ANALYSIS OF TC4 TITANIUM ALLOY DURING ELECTROPLASTIC EFFECT

摘要:

采用Gleeble-1500D热-力学模拟机,将不同晶粒度的TC4试样分别以0℃/s、10℃/s、30℃/s、50℃/s和70℃/s的升温速度加热至700℃进行单向压缩并得到流变应力曲线图,结合SEM、TEM等研究了电流作用下TC4钛合金高温压缩过程中流变应力的变化及影响因素。结果表明,无电流时流变应力超过1000MPa,电流作用下可降至600MPa以下。小电流下TC4试样发生动态再结晶,应力随应变快速增大到应力峰值,后又快速下降至稳定状态；大电流下发生动态回复,局部有动态再结晶,无应力峰值,应力最大值低于400MPa,且电流越大,β相转变为α相的相变越完全。分析认为,TC4钛合金的流变应力受电流大小、动态再结晶和相变的共同影响,电流促进动态再结晶和相变并降低流变应力。

Abstract:

TC4 titanium alloys with different grain sizes were heated to 700℃ and compressed uniaxially using a Gleeble-1500D thermal mechanical simulator. Heating rates of 0, 10℃/s, 30℃/s, 50℃/s, 70℃/s were used for the heating process. The flow stress of the TC4 titanium alloys during the high temperature compression was investigated under the effects of the current by flow stress curves, SEM and TEM. It is found that the stress can be reduced from around 1000Mpa to below 600Mpa under the application of the current. Dynamic recrystallization occurs at a low current and the stress increases rapidly with the strain at first and reaches apeak value, it then decreases quickly and eventually become steady with the further increase of the strain. Dynamic recovery takes place at a high current and dynamic recrystallization is only found at some local areas. No stress peak is noticed with a high current and the maximum stress is below 400 Mpa. In addition, a higher current can promote a more complete phase transition from β to α. In conclusion, the flow stress of the TC4 titanium alloys can be affected simulteously by the current, dynamic recrystallization and phase transition and the current can facilitate dynamic recrystallization and phase transition, leading to decreasing flow stress.