Influence of grain boundaries and pre-precipitates on ion implantation-induced precipitation in the V-4Cr-4Ti alloy

The V-4Cr-4Ti alloy which contains the pre-precipitates has been subjected to implantation of high energy ions at room temperature. It was found that the Ti-rich precipitates occur at grain boundaries while the far finer precipitates form within the grains. The ion implantation also results in variation of appearance of the pre-precipitates in the samples. These results indicate that diffusion in the samples is obviously enhanced by ion implantation-induced vacancies. The vacancies will disappear at the grain boundaries and the precipitates/matrix interfaces, which will transfer vanadium atoms prior out of the boundaries or the interfaces due to Kirkendall effect. In this way, the Ti-rich precipitates will form at the boundaries. Meanwhile, the pre-precipitates will change their shape.