Abstract:
The age hardening effect in minor scandium and zirconium added cast Cu-10Al alloys have been studied through isochronal and isothermal ageing at various temperatures for different times. It is observed that significant hardening takes place in the aged alloys due to the precipitation of copper aluminides. Formation of Al3Sc and Al3Zr precipitated through Sc and Zr addition improve the thermal stability of the alloys and Sc addition accelerates the ageing due to precipitates of Al3Sc. It is also observed that thermal conductivity decreases with the increase the ageing temperature due to formation of fine precipitates. The effects of minor Sc and Zr addition on microstructure and recrystallization properties of alloys are also studied by optical microscopy. The results show that Sc and Zr addition can refine grains of the as-cast alloys by precipitation of primary Al3Sc and Al3Zr particles formed during solidification as heterogeneous nuclei. Secondary Al3Sc and Al3Zr precipitates formed during ageing treatment strongly pin the movement of dislocation and subgrain boundaries, which can effectively inhibit the alloys recrystallization.
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