Investigation on Dynamic Friction Properties of Extruded AZ31 Magnesium Alloy Using by Ring Upsetting Method

Abstract

The dynamic friction properties of the extruded AZ31 magnesium alloy of the grain size of 20 mm 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 mm could be obtained by dynamic recrystallization during deformation, is suitable temperature to make superplasticity at the given strain rate. [doi:10.2320/matertrans.P-M2010811]