纯镁在高压扭转处理中的结构及硬度演变

Structural and hardness evolution of pure magnesium subject to high pressure torsion

摘要:

本文研究了纯镁在室温高压扭转处理过程中的结构及硬度演变，系统探索了硬度达到稳态后时晶粒尺寸的演变。研究结果表明，在变形的初始阶段硬度随着应变的增加而增大，并达到一个最大值（~53 Hv），随后硬度随着应变的增加将降低到一个稳定值。然而，当硬度值处于稳态时，晶粒尺寸并不是处于稳态的。在高压扭转的过程中，硬度值随应变的演变和晶粒尺寸随硬度值的演变是不一致的。当硬度值处于稳态时，晶粒尺寸的进一步减小是由于动态回复和动态再结晶照成的位错湮灭。而动态回复和动态再结晶的发生来源于高压扭转过程中的温度上升以及纯镁较低的熔点。

Abstract:

Pure Mg was subjected to high pressure torsion (HPT) at room temperature, and the structural and hardness evolutions were studied. In addition, the grain size evolution during the hardness steady state was systematically investigated. The results indicated that the hardness initially increases with increasing the equivalent strain, reaches a maximum value of ~53 Hv, and then decreases to a steady-state level at large strains. However, although the hardness reaches the steady state, the average grain size does not reach a steady state. The evolution of the grain size is different from the evolution of the hardness during the HPT processing. The continuously decreased grain size during harness steady state may be caused by the annihilation of the dislocations during dynamic recovery or dynamic recrystallization, resulted from the temperature rising during the continuous HPT processing and the low melting temperature of Mg.