INFLUENCE OF HEAT TREATMENT OF SPECIMENS FROM TI6AL4V MANUFACTURED BY THE TECHNOLOGY OF SELECTIVE LASER MELTING ON STRUCTURE AND MECHANICAL PROPERTIES.

Additive manufacturing, in particular, selective laser melting (slM) is a modern method of manufacturing parts and assemblies of a complex geometry from metal powder, which are difficult or impossible to be reproduced in the states of traditional manufacturing. this technology is featured by residual stresses formed at the stage of manufacturing parts. since titanium alloys are characterized by low thermal conductivity, the problem of forming residual stresses is of particular relevance for them and heat treatment for their removal is mandatory for products manufactured using slM technology. since the structural state of products manufactured by slM technology differs from that formed with the use of traditional technologies, it is necessary to study the effect of annealing for residual stress removal on mechanical properties and microstructure of ti6al4V alloy manufactured by SLM technology. The specimens were studied after annealing with an exposure time of 1-5 h at 800 °C. It was found that as compared to the initial state after manufacturing, the ultimate strength after heat treatment for 1-5 h undergoes a decrease by 20.55--23.03 % and relative elongation has an increase by 31.33-35.57 %. At the same time, the nature of variation in the values of relative reduction in area is non-uniform: annealing with an exposure of 1 h does not cause significant changes; with an increase in the exposure time to 2, 3, and 4 h, a decrease in this characteristic is observed, respectively, by 9.03; 45.97 and 62.56 % as compared to the initial state; after exposure for 5 h, the value of relative reduction in area undergoes an increase in this characteristic as compared to the values after exposure for 4 h -- by ~26.12 %. according to the results of the correlation analysis of the values of mechanical properties and microstructure parameters, it was found that the shape factor of a-phase lamellas has a high ratio with the values of ultimate strength, and the amount of a-phase is most correlated with the values of relative reduction in area at static tension. [ABSTRACT FROM AUTHOR]