Effect of Pb on Microstructure and Mechanical Properties of AZ91 Magnesium Alloy

In this study, the effect of different amounts of Pb (0, 0.5, 1, 3 wt.%) was investigated on the microstructure and mechanical properties of the AZ91 magnesium alloy. The microstructure and mechanical properties were Studied using optical microscope, scanning electron microscope (SEM), X-ray diffractometer (XRD) and tensile test. The results showed that by adding Pb, the volume fraction of the β- Mg17Al12 phase decreased. It was also found that the grain size by 1 wt.% Pb addition decreased significantly and the formation tendency of the divorced eutectic phase reduced. Furthermore, the optimum amount of UTS and elongation were observed by the addition of 1 wt.% Pb to AZ91 magnesium alloy. UTS and elongation increased from 129 MPa and 2.7% to 160 MPa and 7%, respectively, when the 1 wt.% Pb was added to the AZ91 alloy. The fracture surface observations showed that the fracture mode in these alloys were cleavage and the Pb addition does not change the fracture mode.