Process parameters and interfacial characterization of Ti/Al multi-material structure fabricated by selective laser melting

Abstract

In this paper, Ti6Al4V/AlSi10Mg multi-material specimens were fabricated by selective laser melting (SLM). The influence of process parameters on the interfacial crack was discussed and the formation mechanism of interfacial crack under different process parameters was expounded through the simulation of temperature field. The microstructure, element distribution, phase composition and microhardness of the Ti/Al interface were investigated. The cooling rate and temperature gradient increased with the increase of laser power and scanning speed, which easily led to the interfacial crack. Using chess scanning strategy and increasing the preheating temperature of the substrate could effectively reduce the cooling rate, so as to reduce the stress and avoid the interfacial crack. There was a good metallurgical bonding between titanium alloy and aluminum alloy, the typical molten pool morphology could be seen at the interface. In the heat affected zone near the interface, the grain size of aluminum alloy became coarsen, because the lower thermal conductivity of titanium alloy and heat accumulation in the process of forming aluminum alloy. There were needle-like intermetallic compounds (IMCs) at the interface. According to the results of SEM and EDS, the thickness of IMCs was about 2-4 μm, and the composition of IMCs was mainly TiAl and TiAl₃. The results of XRD showed that there were not only Ti₃Al, TiAl, TiAl₃ IMCs but also TiSi₂ ceramic phase at the interface, which made the microhardness of the interface reached as high as 679 HV.