细晶TC4合金板材超塑性行为及组织演变研究

Research on Superplastic Behavior and Microstructure Evolution of Fine-grained TC4 Alloy Sheets

摘要:

本研究采用恒应变速率法，系统探究了在880-920 °C，0.0005 s-1-0.005 s-1的温度及应变速率条件下细晶TC4合金板材的超塑性行为，并就其超塑变形过程中的微观组织演变表征分析。研究表明，随着超塑变形温度的升高，合金均发生明显的动态再结晶现象，其超塑变形机制也随之改变。在880 °C/0.001 s-1下合金表现为晶界滑动、晶粒旋转和滑动的协同超塑变形机制，TC4合金表现出最佳的超塑性能，延展率高达1039%，应变敏感系数m值达0.51，在920° C/0.001 s-1条件下，合金的超塑性依赖于晶界滑动和晶内位错滑移的共同作用，TC4合金延展率仅为746%，应变敏感系数m值降至0.39，相关结果阐释了不同温度及应变速率下TC4合金超塑性能差异的关键原因，对深入研究TC4钛合金超塑变形过程中复杂的力学行为与变形机制具有重要意义。

Abstract:

The research utilizes the constant strain rate method to systematically investigate the superplastic behavior of fine-grained TC4 alloy sheets under temperature conditions of 880-920 °C and strain rate conditions of 0.0005 s-1-0.005 s-1. Furthermore, the study encompasses a comprehensive analysis characterizing the microstructural evolution during the superplastic deformation. This study reveals that with the elevation of superplastic deformation temperature, the alloy consistently undergoes conspicuous dynamic recrystallization. This phenomenon results the transformation in the superplastic deformation mechanisms of the alloy. At 880°C with a strain rate of 0.001 s-1, the alloy exhibits a cooperative superplastic deformation mechanism involving grain boundary sliding, grain rotation and sliding. Under these conditions, TC4 alloy achieves an elongation of up to 1039%, accompanied by a notable strain sensitivity coefficient (m-value) of 0.51. In contrast, at 920°C with a strain rate of 0.001 s-1, the alloy"s superplasticity predominantly relies on grain boundary sliding and intragranular dislocation glide, resulting in a diminished elongation of 746% and a reduced m-value of 0.39. These research findings elucidate the critical factors behind the varying superplastic performance of TC4 alloy across distinct temperature and strain rate conditions，which is significant to further study the complex mechanical behavior and deformation mechanism of TC4 titanium alloy during superplastic deformation.