Microstructure evolution and reaction mechanism of continuously compositionally Ti/Al intermetallic graded material fabricated by laser powder deposition

Abstract

One-pot synthesis of continuously compositionally intermetallic graded material is desirable for the industries, but has proven to be difficult, as each constituent layer presents distinct crystal structure and microstructure. In this work, we demonstrate that a continuously compositionally Ti/Al intermetallic graded material can be successfully fabricated by a well-controlled laser parameter and powder feeding speed. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), micro-area X-ray diffraction analysis (XRD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) are utilized in characterizing the resulting graded material and its structural signatures. Results show that Ti5Si3, Ti3Al, TiAl, TiAl3 and Ti7Al5Si12 form from the Ti6Al4V side to AlSi10Mg side. Clear phase interface can be seen from SEM and TEM, but no macroscopic cracks appear on the graded or phase boundaries. The elemental distribution indicates the microstructure of gradually changes from initial network structure to columnar and dendritic structure from Ti6Al4V to AlSi10Mg. The hardness of the prepared Ti/Al graded material displays a parabolic shape with a maximum in the middle layers. Our findings suggest that continuously compositionally Ti6Al4V/AlSi10Mg intermetallic graded material could be synthesized in one time through laser powder deposition, and the continuously microstructure and hardness implies its application potential in aerospace, especially in the field of space debris protection.