Experimental research on constant-current source ultrasonic strengthening characteristics of 7075-T651 aluminum alloy

7075-T651 aluminum alloy, which is is widely used in aircraft structural parts, exhibits high-strength deformation. This study proposes using ultrasonic impact enhancement technology to improve the fatigue resistance of this alloy and extend its service life. The principle of ultrasonic impact enhancement is based on equivalent impedance control. The surface-strengthening effect is verified via experiments. Results revealed that the surface roughness of the workpiece decreases from an original value of 0.713 μm to as low as 0.353 μm. The microhardness of the surface increases from 201 to 260 HV_0.1. The residual stress of the surface also increases from −25 to −312 MPa. Under the constant impedance threshold, the surface roughness of the workpiece decreases and the surface microhardness as well as residual stress increase with increasing current output. Under the constant output current, the surface roughness of the workpiece decreases to its minimum value, the microhardness gradually increases, and the residual stress reaches its maximum value with increasing impedance threshold.