DTA and TMA Analyses of AZ91D Magnesium Alloys Article Abstract
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Published: May 28, 2006
The phase transformation temperature, the linear expansion coefficient, and the relationships between the microstructure and the thermophysical properties were investigated by DTA (Differential Thermal Analysis), TMA (Thermo Mechanical Analysis), OM (optical microscopy) and XRD(X-ray diffraction) apparatuses for the conventionally solidified (AS-cast) ingot, the rapidly solidified ribbons (RS-ribbons) and their extruded-bars of AZ91D magnesium alloys. The results show that there is a DTA peak about 450℃ for the AS-cast and AS-cast-extrusion-bars, but there is no clearly DTA peak for the RS-ribbon and RS-ribbon-extrusion-bars because the RS-ribbons microstructure is a supersaturated ?-Mg solid solution. According to the microstructure of the RS-ribbon-extrusion-bars, there are very minute quantity of β-Mg17Al12 phase. The linear expansion coefficient of AZ91D alloys is non-linear, the fluctuation amplitude of linear expansion coefficient is the minimum before 225℃. The effects of crystal defects produced by hot-extrusion on the linear expansion coefficient are less than casting defects.