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