Quasi-Static, Dynamic Compressive Properties and Deformation Mechanisms of Ti-6Al-4V Alloy with Gradient Structure

Abstract

Gradient structure metals have good comprehensive properties of strength and toughness and are expected to improve the dynamic mechanical properties of materials. However, there are few studies on the dynamic mechanical properties of gradient structured materials, especially titanium alloys. Therefore, in this study, ultrasonic surface rolling is used to prepare a gradient structure layer on the surface of Ti-6Al-4V, and the quasi-static and dynamic compressive properties of coarse-grained Ti-6Al-4V (CG Ti64) and gradient-structured Ti-6Al-4V (GS Ti64) are investigated. The results show that a GS with a thickness of 293 µm is formed. The quasi-static compressive strength of GS Ti64 is higher than that of CG Ti64. Both CG Ti64 and GS Ti64 exhibit weak strain hardening effects and strain rate insensitivity during dynamic compression, and the compressive strength is not significantly improved. The lateral expansion of CG Ti64 is more obvious, while the lateral side of GS Ti64 is relatively straight, indicating that uniform deformation occurs in GS Ti64. The α phase in the GS produces dislocation cells and local deformation bands, and the lamellar structure is transformed into ultrafine crystals after dynamic compression. Both of them produce an adiabatic shear band under 2700 s−1, a large crack forms in CG Ti64, while GS Ti64 forms a small crack, indicating that GS Ti64 has better resistance to damage. The synergistic deformation of GS and CG promotes Ti-6Al-4V to obtain good dynamic mechanical properties.