Equilibrium solid solubility of nickel to aluminum re-investigated by resistometry

Trace nickel addition improved a property of aluminum bonding wire. Recently some investigators reported equilibrium solid solubility of Ni to Al smaller than previous values. Therefore, its re-investigation is necessary. Wire and sheet of Al–Ni dilute alloys were prepared with total impurity contents less than 15 ppm. After heat treatments at temperatures above 523 K, electrical resistivity was measured at 77 K and 300 K by four contacts DC potentiometry and density-mass method size factor. Resistivity at 77 K, ρD77, after solution treatments showed a good linear relation to Ni contents up to 310 ppm. The 438 ppmNi specimen of the highest content showed a smaller ρD77 than the straight line, suggesting incomplete dissolution of Ni. Contribution per unit concentration of Ni to the ρD77, Δρ77Ni, was 10.4±0.2 nΩm/mass%. Resistivity values at 300 K, ρD300, were at maximum only 1.7% higher than that of ideally pure aluminum. Though linearity of the line was poor, Δρ300Ni was 8.86±1.09 nΩm/mass% and still higher than the Fink et al.'s value. The equilibrium solubility of Ni determined at temperatures ranging 723 K to 913 K is expressed as CeqNi/mass% = 1.36×104 exp(−1.16×104/T), giving maximum solubility about 20% lower than Fink et al.'s.