Abstract:

The microstructure, phase composition of AZ91 magnesium alloy with trace amount of B and rare earth element Gd were investigated by using optical microscopy, scanning electron microscopy (SEM), energy spectrum analysis (EDS) and X-ray diffraction (XRD) analysis. The effects of (B+Gd) microalloying on the microstructure and mechanical properties of AZ91 magnesium alloys were studied at room temperature. The results showed that the rod or block Al2Gd phase was formed after adding the rare earth Gd into AZ91 magnesium alloy. When the content of Gd was 1.0%, the tensile strength of ascast alloy was 207.8 Mpa which increased by 27.9% than that without Gd. After adding the combined (B+Gd) into AZ91 magnesium alloy, the microstructure of alloy changed obviously. Based on reducing the content of Gd, the addition of trace amounts of B could achieve the strengthening effect of trace B instead of some Gd on AZ91. Compared with the ascast AZ91 magnesium alloy with single addition of Gd, in the case of the same mechanical properties, the addition of Gd in the combined (B+Gd) microalloying ascast AZ91 magnesium alloy could save by 19%, which decreased the productive cost of alloys.

Key words: magnesium alloy, Gd, mechanical properties, microalloying, B, microstructure