The microstructure regulation and property enhancement of directed energy deposited Al-Zn-Mg-Cu alloy modified with fixed Si fraction and various TiC contents

Nowadays, Al-Zn-Mg-Cu alloy is widely used in the modern industry due to their extraordinarily high tensile properties, However, the fabrication of Al-Zn-Mg-Cu alloy by directed energy deposition (DED) remains chal-lenging due to its high hot-cracking susceptibility in solidification. In this manuscript, Si and TiC were added into the Al-Zn-Mg-Cu alloy for the elimination of cracks and the enhancement of tensile properties, and the influence of various contents of TiC on the composite material were also investigated. Cracks are removed in all samples, indicating the excellent crack elimination effect achieved by Si and TiC doping. The average grain size first decreases (TiC content <1 wt%) and then increases (TiC content > 1 wt%) with the increase of TiC mass fraction, and it reaches the minimum (14.6 mu m) at a mass fraction of 1 wt%. The hardness and tensile strength are elevated as the TiC content rises and reach maximum (124 HV and 297.3 MPa) at 2 wt%, which are further increased to 132 HV and 355.6 MPa after T6 treatment. It is thus confirmed that the incorporation of Si and TiC enables the fabrication of Al-Zn-Mg-Cu matrix material with crack free microstructure and outstanding mechanical properties.