FATIGUE CHARACTERISTICS OF Ti-6Al-4V TITANIUM ALLOY PRODUCED BY SELECTIVE LASER MELTING

Abstract

Extensive studies of the physical, mechanical and fatigue properties of Ti-6Al-4V titanium alloy samples produced selective laser melting and hot rolling technology have been carried out. For each type of samples the values of the yield strength, tensile strength, elongation to failure, yield strength under compression, microhardness, Young's modulus and density were obtained. In particular, it is shown that the strength limit of the samples produced by selective laser melting is 1300 MPa and exceeds by 30% the corresponding value for samples produced by hot rolling. The density of samples produced in optimal modes of selective laser melting reaches 99,3% of the density of samples produced by hot rolling. Low-cycle fatigue curves are got for Ti-6Al-4V titanium alloy samples produced by selective laser melting and hot rolling. A comparison of the nature of failure on samples produced by these technologies is carried out. It is shown that at high cycle stresses (more than 900 MPa), the fatigue life of samples produced by selective laser melting significantly exceeds the endurance of samples produced by hot rolling. A material with such properties can be used in products (parts) that work for a short time under extreme overload conditions. High values of strength characteristics are associated with a thin needle-like microstructure of the martensitic type with a high content of a'-phase, which is formed in the process of layered laser fusion due to the high crystallization rate, which can reach 105-107 K/s. The paper demonstrates the possibilities of the selective laser melting to creating a promising titanium alloy for the manufacture of Ti-6Al-4V osteointegrable medical devices with characteristics corresponding to or exceeding the characteristics of the material obtained by the traditional hot rolling method.