Influence of spark plasma sintering (SPS) processing parameters on microstructure and mechanical properties of nickel

The influence of variations in the processing parameters employed during spark plasma sintering (SPS) of elemental nickel powders on its microstructure and mechanical properties (i.e., tensile yield strength and ductility) has been investigated in a systematic manner. Bulk polycrystalline nickel samples were fabricated from high purity micron-size powder via SPS for three different pressures (i.e., 50, 65, and 80 MPa) and three different temperatures (i.e., 700, 850, and 1000 degrees C). These SPS processed nickel samples exhibited an average grain size ranging from 5 to 45 mu m, tensile yield strength ranging from 130 to 278 MPa, and ductility ranging from 40% to 60%. The results clearly indicate that as compared to the sintering pressure, the sintering temperature plays a more dominant role in controlling the grain growth and mechanical properties of SPS processed pure nickel. A quantitative Hall-Petch relationship, relating the yield strength to the grain size of SPS processed nickel, has been developed. (C) 2014 Elsevier B.V. All rights reserved.