STABILISATION OF MARTENSITE IN DUAL PHASE MICROSTRUCTURE +1` OF CuZnAl ALLOY
Abstract
Transmission electron microscopy and differential scanning calorimetry were used to study stablised and unstabilised series of the dual phase (?+ martensite) microstrustures of Cu22Zn4,6Al alloy. The volume fraction of the phases was controled by alloy quenching from various temperatures of ?+? zone. It was shown that in stabilised microstructures the As temperature is increased by 15K, which is accompanied by decreasing of the antiphase domain size, monoclinicity angle, by acceleration of disordering as well as by the configuration changes in Cu and Zn atom positions on every third layer of basal planes.
The decreasing of the antiphase domain, which was accounted as ordering degree, was more marked at lower quenching temperatures.The acceleration of disordering appeared at DSC plots as second endothermic peak in range of 170-200°C independently on quenching temperature. In unstabilised samples such peak did not appeared. The extra reflexions at positions forbidden structurally in the [100] zone electron diffraction patern, observed only in stabilised samples were regarded as atributable to configurational changes in martensite according to Pelegrina et all [6]. The monoklinicity angle which changed in range 88-90° was measured at the [110] zone electron diffraction paterns.
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