Interfacial microstructure and stress characteristics of laser-directed energy deposited AA2024 on Ti6Al4V substrate.

• Obvious cracks are found at the Ti/Al interface on both ends with the increase of the number of deposition layers. • The intermetallic compounds thickness for 5 deposit layers is 2.67 times that for 1 deposit layer. • The residual stress at the Ti/Al interface is concentrated at both start and the finish ends of the deposit layer. • The residual stress and intermetallic compounds both contribute to the cracking at the Ti/Al interface. In this paper, different number of AA2024 layers was deposited on Ti6Al4V substrate by using L-DED technology as a preliminary study for the additive manufacturing of Ti-Al dissimilar metal structures. Obvious cracks were found at both ends of the Ti/Al interface when the number of deposition layers was increased to five. To investigate the cracking mechanism, the microstructure at the Ti/Al interface were investigated at first. Continuous intermetallic compounds (IMCs) were formed at the Ti/Al interface. The IMCs were smooth on the side adjacent to Ti6Al4V, and were irregular on the side adjacent to AA2024. The thickness of IMCs increased with the increase of the number of deposition layers. The IMCs thickness for 5 deposit layers was 2.67 times that for 1 deposit layer. Then, the temperature and stress were computed with finite element method. The results showed that the residual stress at the Ti/Al interface was concentrated at both start and finish ends of the deposit layer, and the residual stress increased with the increase of the number of deposition layers. It can be concluded that the cracking at the Ti/Al interface resulted from the increases of the concentrated residual stress and the thickness of IMCs with the increase of the number of deposition layers. [ABSTRACT FROM AUTHOR]