Investigation of Dynamic Friction Properties of Extruded AZ31 Magnesium Alloy
by Ring-Typed Compressive Testing

Abstract

The dynamic friction properties of the extruded AZ31 magnesium alloy of 20 μm grain size were investigated by ring compression test at 523, 548 and 573 K and a rate of 1.0 x 10^-2 s^-1, where all the initial testing conditions were characterized by the climb-controlled dislocation creep. The MoS₂ lubricant maintained lower dynamic friction coefficient (m value) than the oil lubricant. The difference in m values between the machined surface and polished surface was unclear. The m values for WC-Co and diamond-like carbon (DLC) tools were similar in the MoS₂ lubricant. The m values for the DLC tool were lower than those for the WC-Co tool in the oil lubricant. The extrusion direction affected the friction properties. The aspect ratio of the inner diameter at 90° to the extrusion direction after testing was almost isotropic; on the other hand, the anisotropy occurred at 0° and 45°. The extent of anisotropy at 548 K was the highest, although the lower the temperature, the higher the critical shear stress of the non-basal plane. The condition at 523 K, where fine grain sizes less than 3 μm could be obtained by dynamic recrystallization during deformation, is suitable for making superplastic at the given strain rate.