Comparative analysis of VT6 titanium alloy in structural states with enhanced mechanical properties

Abstract

The paper describes the results of comparative studies of the mechanical properties of VT6 titanium alloy (Ti-6Al-4V) with a standard equiaxial microcrystalline structure (MC) with an average grain size of the ? phase of 5-15 ?m, a homogeneous submicrocrystalline structure (SMC) with an average grain size (fragments ) 0.5 ?m and a bimodal submicro-micrograin structure consisting of a matrix with an average grain size (fragments) of 0.8-1.5 ?m with inclusion of ?-phase grains of about 5 ?m in size under static, dynamic and cyclic loading. It is shown that an alloy with a homogeneous SMC structure has increased hardness, strength, and fatigue resistance in comparison with MC, however, the toughness in the SMC state is significantly lower than in the MC state, which reduces the prospects for using an alloy with such a structure. Of practical value is an alloy with a bimodal structure, which, with comparable hardness, strength, and fatigue resistance characteristics comparable to the SMC state, has a markedly higher ductility and impact strength, the value of which for specimens with induced fatigue crack (CTF) is 0.15 MJ / m2, which is significantly higher than in an alloy with an SMC structure - 0.08 MJ / m2, which allows us to predict high survivability in parts made of an alloy with a bimodal structure, which is technologically easier to form than an SMC. The performed assessment of the mechanical properties allows us to develop general recommendations regarding the formation of the microstructure type and the size of the structural components in the VT6 alloy, depending on the magnitude and conditions of loading, the expected operating temperature of the parts.