Možnosti přípravy intermetalických slitin TiAl pomocí 3D tisku ze směsi prášků na bázi Ti a Al

Abstract

The preparation of a Ti-44Al-1.7V-0.2Mg-4.5Si alloy from a mixture of Ti6Al4V and AlSi10Mg powders by SLM and HIP were studied. It was found that the course of SLM is significantly affected by the exothermic reaction and therefore is necessary to use low laser powers and higher Hatch spacing and scan speeds to construct prints of the designed dimensions. The use of other printing parameters resulted in significant warping, which made preparation by SLM impossible. Cracks and porosities including un-melted Ti powder particles were observed in the microstructure after SLM, even with the use of appropriate parameters that enabled the construction. HIP (hot isostatic pressing) enabled significant elimination of cracks and pores by up to 90 %, as well as significant homogenization including elimination of un-melted Ti powder particles. Subsequent heat treatment (HT) modified the microstructure to duplex type contained high amount of γ-TiAl phase, α2-Ti3Al phase and Ti5Si3 precipitates. Hardness, compressive yield strength, compressive strength, and plastic deformation at RT (room temperature) were higher in the direction perpendicular to the printing direction than in the parallel direction which indicates anisotropic behavior. Hardness, yield strength at RT and mechanical properties at higher temperatures showed similar values to cast or powder metallurgy prepared low-alloyed TiAl alloys with a duplex or near gamma type of microstructure. The influence of individual preparation steps on the microstructure and mechanical properties was also studied and discussed.