Effect of Si on Phase Equilibria, Mechanical Properties and Tribological Behaviour of Al-Cu Alloy

In the current work, novel Al-rich Al 90-X Cu 10 Si x (x = 2.5 at%, 5 at%, 7.5 at%) ternary alloys were used to evaluate the effect of Si on Al-Cu alloy in an effort to design and develop new lightweight metal alloys with unique microstructure as well as superior mechanical and good wear resistance properties. The solidification behaviour of the studied alloy was predicted by thermodynamic simulation using the ThermoCalc software and compared with experimental results. The microstructure of the studied Al-rich ternary alloys reveals the presence of dendritic phases (i.e., L → L + α-Al) followed by peritectic reaction (i.e., L + α-Al → Al 2 Cu) or eutectic reaction (i.e., L → α-Al + θ-Al 2 Cu) and finally the evolution of ternary eutectic reaction (i.e., L → α-Al + θ-Al 2 Cu + β-Si) for the investigated Al-Cu-Si alloys. It is found that the hardness increased from 150 ± 6.64 HV to 221.9 ± 6.81 HV with the addition of Si from 2.5% to 7.5%. The least wear scar depth of 48 μm is obtained for Al 87.5 Cu 10 Si 7.5 alloy, signifying better wear resistance properties as compared to other alloys. The wear property is found to be 14.2 KN-m/mm 3 for AlCuSi 7.5 alloy, which is better as compared to the wear properties of AlCuSi 2.5 alloy (i.e., 6.9 KN-m/mm 3 ) at a particular load of 5 N. It is also observed that the wear resistance and microhardness properties increase with the addition of Si % with the slight reduction of tensile strength from 240 MPa to 215 MPa.