Abstract
Resistivity changes during heat treatment and effects of solution treatment on aging behavior were investigated for an extruded ZK60 magnesium alloy containing 4.8%Zn, 0.52%Zr and Mn, Si and Pb less than 0.04% as impurities. Change in resistance ratio R(=ρ300/ρ77) with isochronal aging well corresponded with age-hardening. The increase in the solution treatment temperature resulted in the decreased R and increased resistivity ρ due to increased solute Zr concentration. The higher solution temperatures resulted in the increased maximum hardness and decreased incubation period aging. Particles containing Zn and Zr were observed remaining even after solution treatment at 773K for 36ks. Activation energy for the nucleation of precipitates below 473K was determined to be 70.5 to 76.3kJ/mol based on the incubation period for change in R. Empirical relation between R and ρD77. for the present alloy was obtained as follows: 11<ρD77/nΩm=43.3/(R-1)-0.584<23. Comparing the numerator of this equation with previously reported ρ values for the purest magnesium, the contribution of dissolved Zn in Mg to ρ was expected to increase with increasing temperature for the ρ measurement.
