Alternative Liquid-Assisted Sintering of Al/Cu Composites Using Selected Powders of As-Cast Al-Zn Alloy

Abstract

Al and its alloys constitute one of the most versatile, economical, and attractive materials for a wide range of applications. The 7xxx and 2xxx series alloys achieve the highest mechanical strength among the aluminum alloys. In this investigation, powder metallurgy is used to characterize the microstructural and mechanical properties of a noncommercial Al6Cu5Zn alloy. Initial powder sizes are determined, and the best conditions are obtained for distribution between 75 and 106 μm. The samples are sintered at 585 °C, 600 °C and 615 °C for 0.5, 1.5 h and 3 h. Similar mechanical behavior to that of the as-cast Al-Cu-based alloys is attained (~125 MPa) for the samples sintered at 615 °C for 3 h. In terms of a reduction in energy consumption and in the metal fumes commonly evidenced by foundry applications, Al-Zn powders have the potential to be associated with Al and Cu powders in an Al6Cu5Zn composite constitution.

Oxidative and abrasive wear of multiphase AlSi0.75TiMnFeCux (X = 0, 0.25, 0.5) high entropy alloy under non-lubricating reciprocating motion

“…In this HEA, the elements easier to melt are Al (660°C) and Cu (1085°C) as compared to other elemental constituents. Therefore, Al-Cu liquid phase sintering occurred during SPS and a considerable fraction of liquid phase below the melting temperature of Al favoured the liquid phase sintering [42]. However, increasing Cu to 0.5 mol% enhanced the growth of the AlCu-rich phase and promoted their segregation in the BCC matrix.…”

“…A noticeable reduction in hardness was found when Cu = 0.5% is added to AlSi 0.75 TiMnFe HEA. This can be attributed to the increase in grain boundaries of low melting AlCu-rich phases due to liquid phase sintering effects during SPS [42].

Figure 7 (a) Density and (b) microhardness of AlSi 0.75 TiMnFeCu 0.5 HEAs ( x = 0, 0.25, and 0.5 molar ratios).

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“…As previously mentioned, the addition of Cu to AlSi 0.75 TiMnFeCu x HEAs results in the segregation of alloying elements to form an L 21 and µ-phase, as Cu has a positive mixing enthalpy [42]. This leads to an increase in the theoretical and as-milled density of the HEAs.…”

“…Overall, the superior wear resistance of AlSi 0.75 TiMnFeCu 0.25 and AlSi 0.75 TiMnFeCu 0.5 HEA/WC pairs can be attributed to their multiphase microstructures containing Al-, AlCu rich with harder IMCs and Laves phases in the BCC matrix. In contrast, the AlSi 0.75 TiMnFe HEA had a higher fraction of brittle IMCs and Laves without soft Al-, Cu-rich particles, which acted as scratching centres during reciprocating motion and wear out the tracks easily [31,42,46,49].…”