Speed function effects on properties of Ti-5Al-5Mo-5 V-1Cr-1Fe alloy manufactured by electron beam melting

Abstract

The speed function (SF) parameter, which is a unique combination of beam speed and beam current, is one of the most important parameters of the electron beam melting (PBF-EB) production process. It allows the same process conditions (size of the melt pool, process temperature, etc.) to be maintained for parts with different geometries and sizes. The aim of this research was to understand the effect of SF on the Ti-5Al-5Mo-5V-1Cr-1Fe alloy produced by electron beam melting technology. The results showed that increasing the SF from 86 to 116 resulted in a decrease in the average process temperature, a decrease in the length of the α phase plates, and change in the proportion of α and β phases from 53% (SF 86) to 50% (SF 116) of the β phases. Differences in microstructure (column diameters, thickness, and length of α-phase plates), phase composition, microhardness, porosity at the bottom, and top of the samples were observed on all samples. The mechanical property analysis did not show a significant effect of SF on elongation, but an increase in SF from 86 to 96 resulted in an increase in ultimate tensile strength (UTS) of approximately 7%, whilst an additional increase to 116 resulted in a decrease in UTS of approximately 8.5% compared to SF 96. From the results, it can be seen that the microstructural and mechanical properties of the material strongly depend on the SF. Based on it, SF 86 can be considered as the recommended value for the manufacture of Ti-55511 alloy parts.