Martensitic phase transformation of Cu-Zn-Al alloy, induced by cold rolling deformation

The purpose of this paper is to study the phase transformation induced by the cold rolling of a Cu- Zn-Al alloy fabricated in our laboratories. Flat specimens were made from the alloy. They were subsequently heat treated at 850°C/20 min, quenched in water at 100°C, treated at 320°C/30 min, quenched in water at 100°C, cooled in air up to room temperature. To correlate the microstructure variations with the entity of the imposed deformation, the samples were cold rolled selectively (each 2.5%) up to 15% of deformation. On each cold rolled sample, the microstructures were investigated by LOM and XRD. The deformation has contributed to β3 (L21) ordering of the structure and to occur the martensitic transformation. The martensite obtained is the M18R type. This result shows that the parameter which most influences the type of obtainable martensite is determined by the order of the parent phase. During testing it was found that the martensite enucleates in appreciable quantities even at a level of deformation of 2.5% of the specimen. An increase of the martensite up to a deformation of 15% was observed. It has not been possible to continue beyond this level of deformation, due to the presence of transgranular cracks.