Effects of Silicon Content on the Mechanical Properties and Lubricated Wear Behaviour of Al–40Zn–3Cu–(0–5)Si Alloys

Abstract

In this work, one ternary Al-40Zn-3Cu and seven quaternary Al-40Zn-3Cu-(0.25-5)Si alloys were synthesized by permanent mould casting. Their microstructure, mechanical and lubricated wear properties were investigated using appropriate test apparatus and techniques. As the silicon content increased the hardness of the alloys increased, but their elongation to fracture decreased. Tensile strength of the alloys decreased with increasing silicon content following a sharp decrease and a slight increase. Among the silicon-containing quaternary alloys the highest and the lowest tensile strength values (348 and 305 MPa) were obtained with the Al-40Zn-3Cu-2Si and Al-40Zn-3Cu-5Si alloys, respectively, while the base alloy (Al-40Zn-3Cu) exhibited a tensile strength of 390 MPa. However, the volume loss due to wear of the alloys increased with increasing silicon content after showing an initial increase and a sharp decrease. The lowest wear loss was obtained with the alloy containing approximately 2% Si which has the highest tensile strength among the quaternary alloys containing more than 0.25% Si. Wear surfaces of the alloys were characterized mainly by smearing indicating that adhesion is the dominant wear mechanism for the experimental alloys.

Influence of Test Conditions on the Lubricated Friction and Wear Behaviour of Al–25Zn–3Cu Alloy

“…It is known that as the pressure increases the oil film thickness decreases in lubricated systems [1][2][3][4][19][20][21][22][23]. The decrease in the oil film thickness may cause metal-to-metal contact in the early stages of the wear tests [19][20][21][22][23].…”

“…It has been shown that zinc-based alloys can be successfully replaced by aluminium-based alloys for tribological applications [1][2][3]. Extensive research on the aluminium-based alloys resulted in the development of ternary Al-40Zn-3Cu and quaternary Al-40Zn-3Cu-2Si alloys [1][2][3].…”

“…Extensive research on the aluminium-based alloys resulted in the development of ternary Al-40Zn-3Cu and quaternary Al-40Zn-3Cu-2Si alloys [1][2][3]. They exhibited more or less the same specific strength as the zinc-based monotectoid alloys but with considerably higher ductility [4][5][6][7][8][9].…”

Assessment of Hardness in As-Cast and Homogenized Zn-Al-Cu Alloys

“…In order to overcome these limitations, the change in chemical composition has been proposed 5) as an alternative. For instance, recently, it has been proposed 6) to change the base from zinc to aluminum. Replacing zinc with aluminum in the alloy system causes the formation of the stable (CuAl 2 ) with a tetragonal crystalline structure instead of the metastable " phase promoting a considerable higher ductility.…”

“…Replacing zinc with aluminum in the alloy system causes the formation of the stable (CuAl 2 ) with a tetragonal crystalline structure instead of the metastable " phase promoting a considerable higher ductility. 6) Therefore, the purpose of this work was to investigate the effect of change in chemical composition on the microstructure and mechanical properties, hardness, in order to establish a relationship which enables us to assess the hardness in the as-cast and homogenized alloys.…”