Micro-Vicker's-hardness of five typical phases obtained by different kinds of heat-treatment of Cu-Al eutectoid alloys were measured, comparing with their phase-transformations occurred in heating them from room temperature.
Fundamental phase-transformation process of quenched specimen which had already been observed in micro-structual, specific heat, electric resistance and X-ray investigations, β'→β1→P→β was also verified by the results of the above high-temperature hardness testing.
But both an abnormal transition observed between 200°C-300°C during tempering process of β' phase and a pearlitic decomposition at high-temperature heating of μ phase which is transformed after long time heating at lower temperature below the eutectoid temperature, are left unexplained.