Properties of nano-structured pure Al produced by mechanical grinding and spark plasma sintering

Air-atomised pure aluminium powder was mechanically grinded (MG) using a vibrational ball mill, and mechanically grinded powder was sintered by spark plasma sintering (SPS). Solid-state reactions of MG powder after various heat treatments were studied by X-ray diffraction (XRD). The mechanical properties of the SPS materials were evaluated by hardness and compression testing. Characterisations of the solid-state reactions between the MG powder and process control agent (PCA) after heating at temperatures from 573 to 873 K for 24 h suggested the following products. No solid-state reaction was observed after heating up to 573 K for 24 h. Formation of γ-Al2O3 occurred in the 4 h MG powder after heating at 773 K for 24 h, whereas the mixture of γ-Al2O3 and Al4C3 was observed in the 8 h MG powder after heating at 773 K for 24 h. The full density of the SPS material was obtained with the condition of applied pressure at 49 MPa at 873 K for 1 h. The Vickers hardness of the SPS material produced from no MG process and 64 h MG powders exhibited HV39 and HV159, respectively, and the SPS material based on no MG process and 8 h MG powders showed room temperature compressive proof stresses of 173 and 440 MPa, respectively.