Microstructural evolution and vibration fatigue properties of 7075-T651 aluminum alloy treated by nitrogen ion implantation

The effects of nitrogen ion implantation on the microstructures and the vibration fatigue properties of the 7075-T651 aluminum alloy were investigated. Nitrogen ions were implanted into 7075-T651 aluminum alloy by metal vapor vacuum arc (MEVVA) at the dose of 3 x 10(17) ions/cm(2) at room temperature. The trajectory distribution range and the introduced defects of nitrogen ion-implanted 7075-T651 aluminum alloy were simulated using the Stopping and Range of Ions in Matter software. The phase composition was tested by X-ray diffraction (XRD), the microstructures were characterized using a transmission electron microscope (TEM), and the fracture mor-phologies of vibration samples were observed using a scanning electron microscope (SEM). Experimental results indicate that the fatigue life of the ion-implanted vibration samples increased by 75% compared with the un-treated samples. The ion implantation caused the microscopic strain,which increased the density of dislocation structure and reduced the grain size. The gradient microstructure and fracture properties of the sample were analyzed. The results show that the high-density dislocation and fine grains induced by ion implantation are beneficial to prolong the vibration fatigue life.