The Role of cobalt and nickel intermetallic phases on the mechanical properties and microstructure evolution of Al-Zn-Mg-Cu alloys

Abstract

In this study, the effects of cobalt and nickel additions on microstructure evolution and mechanical properties of Al-Zn-Mg-Cu alloys produced by chill casting process were investigated. Al-Zn-MgCu aluminum alloys containing Ni and Co additives were homogenized at different heat treatment conditions, aged at 120°C for 24 h, and retrogressed at 180°C for 30 min then re-aged at 120°C for 24h.Comparison of the ultimate tensile strength of the Al-Zn-Mg-Cu base alloy underwent RRA temper process with that of the base alloy underwent a similar heat treatment process after the addition of 0.5 wt. % Ni and 0.5 wt. % Co showed that the gains of tensile strengths of the orders of 100 MPa and 135 MPa were attained respectively. These improvements are attributed to phase dispersion particles of the formation of Ni and Co-rich such as and Co intermetallic dispersoids retarded the grain growth, led to grain refinement and precipitation hardening and resulted in further strengthening of the Al alloy. Microstructure characterization of the alloys was carried out using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD).

Effect of Co and Ni Addition on the Microstructure and Mechanical Properties at Room and Elevated Temperature of an Al–7%Si Alloy

“…These intermetallics may have nucleated on some of the TiB 2 particles, thus rendering them inactive for nucleation of a-Al. However, this result is contradictory to the findings by Naeem et al 12 who found that grain refinement occurred on addition of Co and Ni to an Al-Zn-Mg-Cu alloy.…”

Alternative Liquid Assisted-Sintering of AL/CU Composites Using Selective Powders of AS-Cast Al-ZN Alloy

“…The mechanical properties and application the both automotive and aircraft parts of Al-alloys are dependent of added elements [1,3]. Metallic and non-metallic elements such as Fe, Cu, Pb, In, Zn, Ni, Mg, Si, Ti, Sn, etc; are responsible to improve the mechanical properties when commercial alloys Al-based are investigated [2,[4][5][6][7]. When Zn content is utilized, a liquid phase formation in an Al-Cu binary system is formed [8].…”