The plastic deformation and fracture characteristics of two gold-platinum alloys strengthened by spinodal decomposition have been experimentally investigated. It was found that the fracture path in these alloys is primarily intergranular; this is caused by incoherent grain, boundary precipitation of the equilibrium phases. The grains themselves are not embrittled by the transformation. It was also found that the initial work-hardening rate is higher than normally observed, and that the proportional limit is appreciably increased by spinodal decomposition. A new theory was advanced to account for the work-hardening behavior, and it is in good agreement with experimental results. It was also shown that present theories cannot account for the large increase in proportional limit.
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