Comparative study on high temperature deformation behavior and processing maps of Mg-4Zn-1RE-0.5Zr alloy with and without in-situ sub-micron sized TiB2 reinforcement

Abstract

Mg-4Zn-1RE-0.5Zr (ZE41) Mg alloy is extensively used in the aerospace and automobile industries. In order to improve the applicability and performance, this alloy was engineered with in-situ TiB 2 reinforcement to form TiB 2 /ZE41 composite. The high temperature deformation behavior and manufacturability of the newly developed TiB 2 /ZE41 composite and the parent ZE41 Mg alloy were studied via establishing constitutive modeling of flow stress, deformation activation energy and processing map over a temperature range of 250 °C - 450 °C and strain rate range of 0.001 s −1 - 10 s −1 . The predicted flow stress behavior of both materials were found to be well consistent with the experimental values. A significant improvement in activation energy was found in TiB 2 /ZE41 composite (171.54 kJ/mol) as compared to the ZE41 alloy (148.15 kJ/mol) due to the dispersed strengthening of in-situ TiB 2 particles. The processing maps were developed via dynamic material modeling. A wider workability domain and higher peak efficiency (45%) were observed in TiB 2 /ZE41 composite as compared to ZE41 alloy (41%). The Dynamic recrystallization is found to be the dominating deformation mechanism for both materials; however, particle stimulated nucleation was found to be an additional mode of deformation in TiB 2 /ZE41 composite. The twinning and stress induced cracks were observed in both the materials at low temperature and high strain rate. A narrow range of instability zone is found in the present TiB 2 /ZE41 composite among the existing published literature on Mg based composites. The detailed microstructural characterization was carried out in both workability and instability domains to establish the governing deformation mechanisms.