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Solution plus ageing leads to the precipitation of finer and more homogeneous γ′ precipitates in comparison to direct ageing. Solution treatment at 1220 °C eliminates the large primary γ′ phase and replaces them with homogeneous secondary γ′ precipitates. Coarsening of γ′ particles according to Ostwald ripening mechanism is confirmed. An increase of the critical resolved shear stress (CRSS) is observed for the under-aged specimens, followed by a maximum of CRSS at γ′ particle size of around 100 nm and a decrease of CRSS for the over-aged specimen. This result agrees well with the highest yield strength and microhardness of the 750 °C × 24 h aged specimens.

Selective laser sintering (SLS) technique is capable of rapidly fabricating customized implants with porous structure. A simple encapsulation process was developed to coat 316L stainless steel (316L SS) powder with ethylene-vinyl acetate copolymer (EVA). Subsequently, porous 316L SS was prepared by SLS preforming of EVA-coated metal powders, debinding and sintering in hydrogen atmosphere. The effects of processing parameters on pore characteristics and mechanical properties were analyzed. The results indicate that the porosity of green body mainly depends on laser energy density, while the pore features and mechanical properties of sintered specimens are largely dominated by sintering temperature. After sintering at 1100–1300 °C, the average pore size and porosity are 160–35 μm and 58–28%, respectively. In addition, the elastic modulus and compressive yield strength are 1.58–6.64 GPa and 15.5–52.8 MPa, respectively. It is revealed that the pore structural parameters and mechanical properties of the as-sintered porous 316L SS can be controlled readily to match with those of cancellous bone by modification of SLS processing parameters and subsequent sintering temperature.

Powder cobalt base superalloy prepared by high-energy balling and spark plasma sintering are studied through metallography and compression test. The experimental results shows that the powder size and crystalline grain decrease and distortions of crystal lattice increases with milling time. These trends slow down after milling for 8 h. Addition of 1.5% methanol can lessen powders adherence and agglomeration. The relative density of the sintered compact is 99.2% by spark plasma sintering at 1100 °C and 40 MPa. Its microstructure is fine with average grain size below 5 μm. Its compression strength and elongation are 2506 MPa and 2.5%. Annealing heat treatment at 1300 °C can improve its elongation but decrease its strength. They are 23.0% and 1982 MPa, respectively. The added nano-particles Y2O3 are changed into Y–Cr–O compounds to strengthen the cobalt base superalloy.