Thermal stability of magnesium fabricated by combination of mechanical milling and spark plasma sintering

Pure magnesium powders together with 0.5 g of process control agent were mechanically milled (MM) using a planetary type of ball mill with different processing times. MMed powders were consolidated into bulk materials by the spark plasma sintering (SPS). Changes in hardness and solid-state reactions of the SPS materials before and after isochronal and isothermal heating at 473 K, 523 K and 573 K have been examined by hardness measurements and an X-ray diffraction. Enhanced hardness was observed in the SPS materials fabricated from MMed 32 h powder after heating at 523 K for 8 h. The value of Vickers hardness in the SPS materials during heating at 523 K increased from 48 to 91 HV, suggesting that hardening ability was 43 HV. Solid-state reaction was clearly observed in all SPS materials fabricated from MMed powders produced with the different MM time after heating at 473 K, 523 K and 573 K. The contribution for enhancement of hardness in the SPS materials was attributable from formation of MgO, MgH2, and Mg(OH)2, typically from MgO. The thermal stability of pure magnesium can be improved by MM-SPS process. © 2019 The Japan Institute of Light Metals.