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In order to measure cantilever bending stress of elastic alloys during stress relaxation experiment, a homo-made apparatus has been developed. The mechanical properties and stress relaxation resistances of three high strength copper alloys have been investigated. Considering different experimental conditions, the Cu-Ni-Sn alloys exhibit the optimum stress relaxation resistance. The mechanisms of stress relaxation and precipitation strengthening have been discussed. The hardness is recommended to be a critical parameter which can be used to evaluate the stress relaxation resistance simply. Because the interactions between precipitation particles and dislocations which influence the hardness also affect the dynamic recovery of mobile dislocations during stress relaxation. Finally, two effective methods have been proposed to slow down the stress relaxation in the copper alloys.

In the paper, the TiC −50 wt.% high manganese steel cermet was made with different sintering processes including vacuum sintering, hot pressing, microwave sintering and spark plasma sintering (SPS). The microstructure, porosity and fracture morphology of the samples were analyzed with scanning electron microscopy (SEM). Phase analysis was carried out using X-ray diffraction (XRD). The density, hardness, transverse rupture strength (TRS) and wear resistance were investigated for the effect of the sintering processes. The results showed that the core–shell structure was not clearly observed for the TiC particles in microstructures and the high manganese steel matrix is BCC structure. Hot pressing, microwave sintering and SPS are useful processes for densification of the cermet. Nearly full density and higher hardness can be reached by these three processes at a lower sintering temperature and in a shorter sintering time. However, higher TRS can be reached by means of alloying completely in a longer sintering time, for example vacuum sintering. Pre-sintering in a long sintering time at a lower sintering temperature is also useful for improving the TRS. Finally, vacuum sintering is an effective process for producing this composite with the lowest cost in the mass production.