Effect of Heat Treatment on Microstructures and Properties of AZ40M Alloy

Abstract

The influence of two-step homogenization on microstructures and properties of AZ40M magnesium alloy were investigated by the scanning electronic microscopy (SEM), X-ray diffraction analysis (XRD) and tensile experiment. Through comparing the microstructure and mechanical properties of the alloy before and after homogenization treatment, a two-step homogenization process of the semi-continuous casting AZ40M magnesium alloy ingot was determined. The result shows that the as-cast AZ40M alloy mainly contained two kinds of second phase, β-Mg17Al12 and Al8Mn5. Treating at temperature of 380 °C for 8 h as the first step homogenization treatment and then treating at temperature of 420 °C for 20 h as the second step homogenization treatment made the eutectic phase (α-Mg/β-Mg17Al12) completely eliminated and the alloying elements such as Al, Zn distributed uniformly. Al8Mn5 is the residual second phase in the homogenized AZ40M alloy. During the homogenization process, the β-phase dissolved which made the content of Al increased in the matrix. The decomposition of β-phase benefits the tensile strength and elongation of the alloy. The tensile fractures of as-cast and homogenization alloys are characteristic of ductile fracture.

Influence of Electrostatic Field on the Microstructure and Mechanical Properties of AZ91 Mg Alloy during Ageing Treatment

“…Al 8 (Mn, Fe) 5 particles can still be seen in the solution‐treated alloy, which means that thermal stability of Al 8 (Mn, Fe) 5 is high due to a high melting point (989 °C). [ 32 ]…”

Al11Mn4 formation on Al8Mn5 during the solidification and heat treatment of AZ-series magnesium alloys

“…It is common in past papers to state that Al8Mn5 is stable (does not transform) during solution heat treatment of AZ80/AZ91, e.g. [17,29,30].…”