Effects of Ni on the microstructure, hot tear and mechanical properties of Al–Zn–Mg–Cu alloys under as-cast condition

Abstract

The effects of Ni on the phases, microstructural evolution, hot tear susceptibility and mechanical properties of Ale6Zn-1.4Mg-1.2Cu alloys fabricated by gravity casting were investigated using X-ray diffraction (XRD), scanning electronic microscopy (SEM), optical microscopy, the N-Tec Hot tear and tensile test. The calculation of phase diagrams (CALPHAD) modelling was also conducted to understand the phase formation of the experimental alloys. The results showed that the secondary phases (including h-MgZn2,SeAl2CuMg and Al3Ni) are mainly distributed at grain boundary, while round SeAl2CuMg particles are also found in a-Al matrix. Ni only exists as Al3Ni with different morphologies and its number density ascends with the increase of Ni content in alloys, which also significantly improves the hot tear resistance. As a result, the increased Ni in the alloys remarkably improves the ultimate tensile and yield strength, while the elongation increases when Ni < 0.6 wt% followed by decreases when Ni > 0.6 wt%.

Single track scanning experiment on the hypereutectic aluminium alloy Al-8%Zn-7%Ni-3%Mg

“…The ESR value descends with an increase in Ni content, but the change is negligible (~ 10 o C). The influence of Ni on the improvement of the HTS index of Al-Zn-Mg-Cu alloys was described in [14]. The key aspect used was the Cracking Susceptibility Coefficient (CSC) developed by Clyne and Davies in [27].…”

“…Our attitude toward the issue of L-PBF of Al-Zn-Mg alloys is slightly similar, but we decided to use nickel instead of silicon. Al-Zn-Mg-Ni alloys based on the [(Al) +Al 3 Ni] are proved to have excellent fluidity and hot tearing resistance [5,14]. Moreover, since there is no interaction between pair Zn/Mg and Ni it is possible to fabricate a natural particulate-reinforced composite material by an increase in Ni content up to hypereutectic concentration.…”

Effect of Y Element on Microstructure and Hot Tearing Sensitivity of As-Cast Al–4.4Cu–1.5Mg–0.15Zr Alloy

“…[9][10][11][12][13] In particular, the addition of rare earth elements can effectively refine the alloy grains, reduce the hot tearing tendency and improve the comprehensive properties of the alloy. [14][15][16][17][18][19] Chen et al 20 and Tao et al 21 studied the effect of La addition on the hot tearing of 2-Series aluminum alloy, and found that La can refine the alloy grain. In addition, the formed Al 6 Cu 6 La phase can change the composition of intercrystalline liquid phase at the late solidification stage and reduce the hot tearing tendency of Al-Cu alloy.…”

Effects of Cu content on microstructure and mechanical properties of rheo-diecasting Al-6Zn-2Mg-xCu alloys

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Despite the high cost and difficult production process, the 7xxx (Al-Zn-Mg-Cu) wrought aluminum alloys are still widely used in aerospace industry due to its wellperforming mechanical qualities and superior fatigue resistance [1][2][3] . Recently, there has been a booming interest in producing cast Al-Zn-Mg-Cu alloys with the goal of lowering production costs and developing shaped products while maintaining outstanding mechanical qualities [4] .Several processes, such as spray deposition, electromagnetic casting, powder metallurgy, semi-solid casting and quick solidification, have been employed

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