METASTABLE EXTENSION OF SOLID SOLUBILITY OF CERTAIN TRANSITION METALS IN Ag UNDER MELT QUENCHING
by NING Yuantao (Institute of Precious Metals; Ministry of Metallurgical Industry Kunming) (Manuscript received 4 December; 1982)
Cite this article:
by NING Yuantao (Institute of Precious Metals; Ministry of Metallurgical Industry Kunming) (Manuscript received 4 December; 1982). METASTABLE EXTENSION OF SOLID SOLUBILITY OF CERTAIN TRANSITION METALS IN Ag UNDER MELT QUENCHING. Acta Metall Sin, 1983, 19(4): 94-101.
Abstract Metastable extension of solid solubility of transition metals, e.g. Fe, Co, Ni, Mn and Zr, in Ag under melt quenching was measured with lattice parameter method. Metastable solid solubility limit, C_(eq)~s, of these elements in Ag, under cooling rate about 10~5-10~6K/s, is 1.0, 1.5, 1.5, 3.0, 48 and 6.0 at.-％ respectively. Different mechanisms of the metastable extension was proposed. The metastable extension of 3 different kind of Ag alloy systems was discussed: eutectic system Ag-Zr; peritectic system of Ag with some simple metals and monotectic system of Ag with Fe, Co, Ni, Cr and Mn. Metastable extension of solid solubility of Zr in Ag is controlled by crystallizing rate of stable intermediate phase AgZr in liquid state. For A-A_mB_n, (or a(A)-A_mB_n) eutectic systems, the extension parameter C_(eq)s/C_(eu) is inversely proportional to the crystallizing rate of stable intermediate phase A_mB_n at eutectic composition C_(eu), and proportional to a parameter J=(C_m-C_(eu))/(C_(eu)-C_(eq)), where C_(eq) is equilibrium solid solubility, C_m is solute concentration of intermediate phase A_mB_n. For monotectic systems of Ag with transition metals Fe, Co, Ni, Cr and Mn, an immiscible gap exists in the liquid or undercooled melt, C_(eq)~s equals to the solute concentration corresponding to intersecting point of the boundary line of immiscible gap with solidus. C_(eq)~s as well as C_(eq)~1 are inversely proportional to parameter (n_(ws)~(1/3))_M/(n_(ws)~(1/3))_(Ag). For peritectic systems of Ag with simple metals, the electron compound with electron concentration e/a= 1.5 restrict further extension of solid solubility, this is the reason why the solid solubility of these systems extending up to the solute concentration with e/a=1.4.
