Microstructure and Hardness Evolution in Magnesium Processed by HPT

Abstract

High pressure torsion provides an opportunity to process materials with low formability such as magnesium at room temperature. The present work shows the microstructure evolution in commercially pure magnesium processed using a pressure of 6.0 GPa up to 10 turns of rotation. The microstructure evolution is evaluated using electron microscopy and the hardness is determined using dynamic hardness testing. The results show that the grain refinement mechanism in this material differs from materials with b.c.c. and f.c.c. structures. The mechanism of grain refinement observed at high temperatures also applies at room temperature. The hardness distribution is heterogeneous along the longitudinal section of the discs and is not affected by the amount of deformation imposed to the material.

Processing Magnesium and Its Alloys by High‐Pressure Torsion: An Overview

“…Multi‐modal grain size distributions were observed in the early stages of HPT processing of a magnesium alloy at high temperatures and also at low temperatures and there is experimental evidence that the mechanism of grain refinement of magnesium subjected to SPD processing at room temperature is similar to that observed at high temperatures . Plastic deformation leads to the formation of new grains along the grain boundaries but, unlike the SPD processing of face‐centered cubic metals, dislocation structures, and subgrain boundaries are not formed in the interiors of the coarser grains in the early stages of deformation.…”

Evaluating the textural and mechanical properties of an Mg-Dy alloy processed by high-pressure torsion

“…Grain refinement is successful without cracking in HPT processing due to the imposed hydrostatic pressure which effectively prevents propagation of fracture during the torsional straining [16]. Several reports are now available describing the application of HPT to pure Mg and Mg-based alloys with the production of average grain sizes down to the nanoscale [14][15][16][17][18][19][20][21]. Some new Mg alloys with high content of RE elements have also been successfully processed by HPT at room temperature [15,[22][23][24][25][26][27].…”

Electrochemical behavior of a magnesium ZK60 alloy processed by high-pressure torsion

“…The EBSD images were recorded from the semi-oval areas of samples in the mid-radius of the TD-RD plane at the near surface position of the disks. Earlier studies provide a more detailed description of the sample preparation for EBSD [33,34].…”