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.

• Periodical: Materials Science Forum (Volume 849)
• Pages: 173-180
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.849.173
• Online since: March 2016
• Authors: Lin Lai, Kui Zhang, Ming Long Ma, Guo Liang Shi
• Keywords: Magnesium Alloy, Mechanical Properties, Microstructure, Two-Step Homogenization

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