Production of AZ91 alloy by hot-pressing method

In this study, it was aimed to produce AZ91 alloys that do not contain any entrapped gas and voids in the microstructure after production. AZ91 alloy was produced by the single-axis hot pressing method, one of the powder metallurgy methods. Hot pressing was carried out for 1 hour at 420, 450 and 500 °C for AZ91 and at 420 and 600 °C for Mg. Pressing pressure was kept constant to be as 50 MPa. Having produced the samples were cut in the dimensions of 5x5x10 mm via wire electrical discharge machining. Densities and porosities were measured by Archimedes' method and X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to examine microstructures. It has been observed that the AZ91 alloy was partially melted during hot pressing at 450 and 500 °C, and the maximum temperature that can be applied to achieve a completely solid state sintering is lower than the eutectic temperature (437 ° C). The AZ91 alloy was found by SEM observations to reach full density after hot pressing at 420 °C for 1 hour. XRD and SEM analyzes revealed that the microstructure was composed of α (Mg-rich) and β (Mg17Al12) phases. The mechanical properties of the alloys and reference materials produced were determined by compression tests at carried out at room temperature, 100, 150 and 200 °C. The mechanical properties of the AZ91 alloy produced by hot pressing were found to be better than those produced by casting methods and values of 183 MPa, 241 MPa and 10.1% were obtained for yield strength, compressive strength and ductility, respectively. As expected, as the test temperature increased, the yield and compressive strengths decreased and the ductility increased.