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.
It has been generally recognized that strength and ductility are in a trade-off relationship in metallic materials. However, we have found that Al–Fe–Si alloy foil containing about 1 mass% of Fe and 0.3 mass% of Si shows high strength and ductility even after cold rolling. We have investigated the effect of Fe on mechanical properties of cold-rolled Al–Fe–Si alloy foil. To the total elongation of cold-rolled Al–Fe–Si alloy foil, the contribution of the elongation after maximum engineering stress in the stress vs. strain curve was found to be greater than that prior to the stress maximum, and the ductility increased with increasing Fe content. The cold-rolled Al–Fe–Si alloy foil exhibits strain rate sensitivity, and the strain rate sensitivity exponent (m value) increased with increasing Fe content. For Al–Fe–Si alloy foil with high m value, shear bands on the surface of the tensile specimen was observed not only in the fracture part, but also in the whole parallel part, after tensile test. The cause of the high ductility in Al–Fe–Si alloy foil having a large Fe content was attributable to the inhibition of the localized necking because of the high m value.