Microstructural Evolution, Mechanical Properties, and Biodegradability of a Gd-Containing Mg-Zn Alloy

Effect of 1 wt pct Gd addition on the microstructural evolution, mechanical properties and bio-corrosion behavior of the biodegradable Mg-4Zn alloy was studied. The average grain size of the base alloy decreased from 14.6 to 5.7 mu m after Gd addition. In contrast to the base Gd-free alloy, a fiber texture with higher intensity of basal poles and lower Schmid factor was formed during the hot extrusion in the Gd-containing alloy. This was attributed to the presence of a relatively high volume fraction of un-recrystallized grains. The respective yield stress (YS) and ultimate tensile strength (UTS) values were significantly improved from 198 MPa and 301 MPa in the Mg-4Zn alloy to 241 MPa and 336 MPa in the Mg-4Zn-1Gd alloy, due to the finer grain size, second phase particles and textural hardening. Extension twins were responsible for achieving the respective high elongations of 33.9 and 20.6 pct for the base and Gd-containing alloys, during tensile loading. Electron backscattered diffraction (EBSD) analysis of the corroded surfaces indicated high pitting susceptibility of the non-basal planes and un-recrystallized grains. Despite the higher stored energy in the Gd-containing alloy due to the lower fraction of recrystallized grains, the finer grain size and the presence of Gd in the corroded layer resulted in improved biodegradability of this alloy.

Automated summary

The study investigated the effect of adding 1 wt pct Gd on the microstructural evolution, mechanical properties and bio-corrosion behavior of a biodegradable Mg-4Zn alloy. The addition of Gd resulted in finer grain size, enhanced textural hardening, and significantly improved mechanical properties. Electron backscattered diffraction analysis showed higher pitting susceptibility in the corroded surfaces of the Gd-containing alloy.