Abstract
The low plasticity of high strength Mg-Gd-Y alloy has become the main obstacle to its application in engineering. In this paper, the origin, propagation and fracture processes of cracks of a solution of treated Mg-13Gd-5Y-3Zn-0.3Zr alloy were observed and studied with scanning electron microscopy (SEM) in an in situ tensile test to provide theoretical references for the development of a new high-performance Mg-Gd-Y alloy. The results showed that there was still some bulk long period stacking order (LPSO) phase remaining in solid solution Mg-13Gd-5Y-3Zn-0.3Zr alloy. Most importantly, it was found that the locations of micro-cracks vary with the different solution treatment processes, mainly including the following three types. (1) At 480 × 10 h and 510 °C × 10 h, much bulk LPSO phase with higher elastic modulus remains in the alloy, which can lead to micro-cracks in the LPSO phase due to stress concentration. (2) At 510 °C × 13 h and 510 °C × 16 h, the phase structure of bulk LPSO changes, and the stress concentration easily appears at the LPSO/α-Mg interface, which leads to micro-cracks at the interface. (3) At 510 °C × 19 h and 510 °C × 22 h, the grain size increases, and the stress concentration is obvious at the grain boundary of coarse grains, which leads to the formation of micro-cracks.
Highlights
Magnesium alloys are mainly used in aerospace, weapon equipment, automobile shell and other fields due to several advantages, including low density, high specific strength and good thermal and electrical conductivity
(2) At 510 ◦ C × 13 h and 510 ◦ C × 16 h, the phase structure of bulk long period stacking order (LPSO) changes, and the stress concentration appears at the LPSO/α-Mg interface, which leads to micro-cracks at the interface
(3) At 510 ◦ C × 19 h and 510 ◦ C × 22 h, the grain size increases, and the stress concentration is obvious at the grain boundary of coarse grains, which leads to the formation of micro-cracks
Summary
Magnesium alloys are mainly used in aerospace, weapon equipment, automobile shell and other fields due to several advantages, including low density, high specific strength and good thermal and electrical conductivity. Adding small amounts of rare earth elements (RE) is a common method of increasing the strength of magnesium alloys. Due to the high solid solubility of rare earth elements in the magnesium matrix and precipitation strengthening, a Mg-RE magnesium alloy (RE/Zn weight ratio >1, RE = Y, Gd, Tb, Dy, Ho, Er, Tm) has wider application prospects in the field of high-strength and heat-resistant industry. As the proportion of rare earth elements in the alloy increases, the room temperature strength and high temperature heat resistance of the alloy increase, but the plastic deformation ability decreases. Due to the closely packed hexagonal structure of magnesium alloy, it has a small number of slip systems, which make its plastic deformation behavior difficult [6,7]. It is necessary to study the deformation behavior and fracture mechanisms of magnesium alloys
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
