FRICTION CHARACTERISTICS OF MAGNESIUM ALLOY ZM-21

Friction plays a significant role in metal working, affecting the flow stress, the deformability, the surface finish, the tool life, etc. Ma gnesium alloy ZM-21 in the wrought condition is used generally in aero space components, the present study being undertaken to assess the sui tability of lubricants for the working of this alloy. The paper descri bes ring compression tests performed on the as-cast material with nine different lubricants in the temperature range 300-500-degrees-C, fric tion factors and flow stresses being determined for the different cond itions. The 'experimentally' determined values of friction factor mu, obtained using the experimental calibration results of Male and Cockro ft have been found to be related to the 'theoretical' friction factor (m, obtained using the theoretical calibration results of De Pierre et al.) through a second-order polynomial. A significant observation was a sharp change in friction factor at about 400-degrees-C. EPMA and di fferential scanning calorimetry (DSC) study of the material indicate t he presence of a metastable phase in the as-cast condition which becam e dissolved during homogenisation at around 350-degrees-C, the rise in friction factor being attributable to this feature.