Cu-Al 2元合金の共析変態へのFe, Zrの影響

抄録

The β→α+γ₂ transformation of Cu-Al binary alloy is depressed at cooling velocity 5°C/min and changes to β→β₁ and β₁→β′ transformations. The tempering processes of the alloy show combinations of β′→β₁, β₁→α+γ₂, β₁→β, β→α+γ₂ and α+γ₂→β transformations, depending on the tempering conditions. In this paper, the effects of Fe and Zr on cooling and tempering eutectoid transformations and on the self-annealing of Cu-Al binary alloy were measured by means of differential dilatation, differential thermal analysis and microscopic observation. The changes in the length of the columnar structure with the β′→β₁ transformation were also discussed. The results obtained were as follows: (1) Some columnar structures of Cu-12.2Al, Cu-12.3Al-1.2Fe and Cu-12.5Al-1.2Zr alloys contracted at β′→β₁. (2) The β→α+γ₂ transformation temperature of Cu-12.3-1.2Fe alloy was lower than Cu-Al binary alloy and that of Cu-12.5Al-1.2Zr alloy was higher. (3) The processes of cooling and tempering transformations of Cu-12.3Al-1.2Fe, Cu-12.5Al-1.2Zr alloys were the same as those of Cu-Al binary alloy, but microstructures of Cu-12.7Al-1.0Fe, Cu-12.7Al-0.7Fe, Cu-12.5Al-1.2Zr and Cu-12.4Al-0.7Zr alloys water-quenched from 800°C were β′+γ′ produced by phase separation. The Al concentrations in these alloys were lower than those in the Cu₃Al type lattices. (4) The self-annealing of Cu-Al binary alloy was depressed by adding Fe and enhanced by adding Zr.