Effect of Multi-Pass Equal Channel Angular Pressing on the Microstructure and Mechanical Properties of a Directional Solidification Mg_98.5Zn_0.5Y₁ Alloy

Abstract

The microstructure evolutions and mechanical properties of a directional-solidification (DS) Mg_98.5Zn_0.5Y₁ alloy during multi-pass equal channel angular pressing (ECAP) were systematically investigated in this work. The results showed that there was a large amount of lamellar structure in the DS alloy. These lamellar structure have almost the same orientation inside the grains. After ECAP, dynamic recrystallization (DRX) occurred and the diameter of DRXed α-Mg grains decreased to 2 µm. During ECAP, large volume fraction of LPSO phase experienced a four-step morphological evolution during ECAP, i.e. original lath → bent lath → cracked lath → smaller particles. Meanwhile, the schematic illustration of recrystallization in the DS-Mg_98.5Zn_0.5Y₁ alloy during ECAP was established. Compression test results indicated that the alloy was markedly strengthened after multi-pass ECAP, and the main reason for the significantly enhanced mechanical properties can be ascribed to the DRXed α-Mg grains, kinking and refined 14H particles.

Fig. 7 The diagram of 14H-LPSO on recrystallization in the Mg_98.5Zn_0.5Y₁ alloy during ECAP.