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Transformation temperature and hardness of the two-phase CuZnAl alloy

The greatest drawback of the CuZnAl-alloys is the difficult control of accurate chemical composition during casting and low resistance to fatigue as result of intercrystal brittleness. This led to a study of the influence of heat treatment in the temperature range of 600 to 680 C, when the controlled ratio of alpha phase in the structure quenched from the balanced alpha+beta field allows the change of the chemical composition of the rest of austenite, which is then reflected on the microstructure, transformation temperatures and hardness. The change of the austenite results in the increase of characteristic transformation temperatures provided there is an increase in betatisation temperature. Depending on the treatment performed, the ratio of alpha-phase in the structure and the size of alpha-grain are changed. Cooling from temperatures higher of 680 C, homogeneous austenite is achieved. The values of hardness, measured at various loads using the Vickers'method, grow linearly with the increase in betatisation temperature.

CuZnAl-alloy; betatisation; transformation temperature; hardness

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