The Effect of Deformation on The Cu Precipition Proccess in The Fe-Cu Alloys

The precipitation process of Cu atoms in Fe-1.0%Cu alloys quenched or aged after quenching and 20% rolled at room temperature was investigated by using the positron annihilation technique. During the isochronal annealing of the specimen above room temperature to 500$^circ$C, the change of the coincidence Doppler broadening (CDB) ratio curve and $S$- and $W$- parameters were observed, showing the nucleation and growth of Cu precipitates in the specimen. This can be interpreted as the result of the enhanced diffusion of Cu atoms by the deformation induced excess vacancies which have the enough mobility in this alloy at room temperature. Microvoids were also observed by position lifetime measurement, but disappeared until 400$^circ$C annealing. The CDB ratio curve almost reached that of the bulk Cu at 500$^circ$C annealing, suggesting that Cu precipitates formed during the isochronal annealing are free from Fe atoms and defects, and positions are trapped in the Cu precipitates