Investigation of acoustic softening and microstructure evolution characteristics of Ti3Al intermetallics undergoing ultrasonic vibration-assisted tension

Abstract

Ultrasonic vibration-assisted deformation (UVAD) technology has been widely utilized in the metallic materials forming and manufacturing process owing to its advantages of effectively reducing deformation stress. However, the intrinsic mechanism of UVAD involved in Ti3Al intermetallics has not yet been clarified. In this research, an ultrasonic vibration tension device for Ti3Al was designed. The mechanical properties under ultrasonic vibration-assisted tension (UVAT) were investigated. Subsequently, the rheological behavior under the effect of ultrasound was analyzed. The influences of the vibration amplitudes and vibration modes on the microhardness and microstructure were explored. The results indicated that Ti3Al behaved obviously an acoustic softening after introducing ultrasonic energy, and the degree of softening was positively correlated with amplitude. There was a “competitive” relationship between the acoustic softening and acoustic residual hardening effects. The maximum stress and microhardness reductions were 206.13 MPa and 6 % when the amplitude was 6.55 μm and 1.31 μm, respectively. The fracture mode evolved from ductility dimple fracture to a mixed-mode of cleavage pattern and brittle fracture. The metallographic organization revealed a “defective phase” structure in the α2 phase and B2 matrix. The amounts of defective phases enlarged with amplitude increasing and extended away from the vicinities of the fracture cross-section.