Enhanced Hardness of Pure Magnesium by MgO Formation Fabricated by Powder Metallurgy

Abstract

Pure magnesium powders together with different amounts of process control agent (PCA) were mechanically milled (MMed) using a vibration ball mill. Stearic acid was used as PCA for the mechanical milling (MM) process. MMed powders were consolidated into bulk materials by spark plasma sintering (SPS). Changes in hardness and solid-state reactions of the MMed powders and the SPS materials have been examined by hardness measurements and an X-ray diffraction, respectively. No solid-state reaction was observed in the MMed powders even when the amount of PCA was increased. At PCA0.50 g, the Vickers hardness of the MMed powders and SPS materials did not improve with increasing a MM processing time. A maximum hardness value of 89 HV obtained in the SPS materials fabricated from MMed 24 h powders with PCA1.50 g. Formation of MgO by solid-state reaction was observed for the SPS materials consolidated from MMed 24 h powders with PCA1.00 g and 1.50 g. Formation of MgO was observed in the SPS materials by increasing the amount of PCA without heat treatments. Enhanced hardness of SPS materials could be attributable for both volume fraction of MgO and sintering temperatures.