Comparison of the microstructure evolution and mechanical properties via MDF and ITMT methods

Abstract

Based on the multi-directional forging (MDF) method under decreasing temperature conditions, intermediate thermo-mechanical treatment (ITMT) method was proposed to control the microstructure of the deformed Mg-13Gd-4Y–2Zn-0.5Zr (wt%) alloy and improve its mechanical properties, especially the yield strength (YS). The results showed that compared with the MDF method, ITMT can significantly improve the mechanical properties of the deformed alloy and shorten the process flow. As the number of deformation passes increased, the microstructure became uniform, the average grain size gradually decreased, and the mechanical properties gradually improved during the MDF process. The average grain size of the alloy after 4 passes exhibited a minimum value of 2.4 µm, and the mechanical properties achieved a maximum value with an ultimate tensile strength (UTS) of 357 MPa and a YS of 304 MPa. The average grain size of the deformed alloy first decreased significantly and then slowly increased with an increase in the number of deformation passes via the ITMT method. After 2 passes, the alloy exhibited the minimum grain size and the best mechanical properties after T4-ITMT and T6-ITMT. The minimum grain size was 3.7 µm, and the UTS and YS were 341 MPa and 320 MPa via T4-ITMT method, respectively. The average grain size was 3.1 µm, and the UTS and YS were 356 MPa and 332 MPa via T6-ITMT method, respectively.