Solid solubility metastable extension of some transition metals in gold

The metastable extended solid solubilities of the transition metals Ti, Zr, Hf, W, Re, Ru and Rh in gold have been studied by measuring the lattice parameters of their gold-rich solid solutions using X-ray diffraction, The cooling rate used for the preparation of the alloys was about 10(6) K/s. It was found that the metastable solid solubilities of Ti, Zr and Hf in gold were 18.2, 13.0, and 13.4 at% respectively, but that those: of W, Re, Ru, and Rh in gold were negligible, It is concluded that metastable extension of the solid solubilities of transition metals in gold is relative to the nature of the phase diagrams of their allays with gold. Under conditions of rapid solidification, the alloys with upper-peritectic-type phase diagrams had significant solid solubility extensions and the alloys with monotectic-type phase diagrams displayed little solid solubility extension. Mechanical alloying may be more effective in producing metastable solid solutions of these alloys.