Abstract
Metallography and electrical resistivity measurements (ρt/ρo) were carried out on an isothermally aged bulk alloy with a substitution composition of Sm(Co0.67Cu0.08Fe0.22Zr0.028)8.45. The as-cast alloy was found to consist of four phases: (A) zirconium-rich phase, (B) samarium- and copper-rich phase, (C) cobalt- and iron-rich phase, and (D) very rich in zirconium phase. After annealing at 1170 °C for 5 h, phase B entered into solid solution, suggesting that the other three phases are the stable phases in this system at this temperature. Large decreases in the electrical resistivity were observed after isothermal ageing at temperatures between 650 and 900 °C inclusive. After an initial decrease in the resistivity values at 650, 700, 750 and 800 °C an increase was observed leading to small peaks. The height of this maximum decreased with increasing ageing temperature and disappeared at 830 °C. This effect can be ascribed to the solubility variations, and an activation energy has been derived from the resistivity peaks.
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