Date of Award

4-1-2022

Publication Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Supervisor

O. Jianu

Keywords

Continuously variable transmission, Aluminum alloys, Automotive industry

Rights

info:eu-repo/semantics/embargoedAccess

Abstract

Light weight alloys like aluminum-silicon (Al-Si) alloys and magnesium alloys are widely utilized in the automobile industry. They have several favorable properties such as high wear resistance and good corrosion resistance at a wide range of temperatures. However, their wear-resistance under harsh operating conditions such as oxidation, creep and thermal fatigue still needs to be improved. In this work, the tribological behaviour of Al-Si alloys die cast A380, die cast ADC10, sand cast A356-T6, die cast B390, and magnesium alloy AE44 were investigated using a block-on-ring tribometer at 93 °C and 130 °C sliding temperatures and fixed sliding speed of 140 mm/s and a load of 200 N.

The wear results of die cast A380 and sand cast A356-T6 were the emphasis of comparison. The results showed that wear rate of sand cast A356-T6 (3.6 × 10−3 mm3/m at 93 °C and 4.7 × 10−3 mm3/m at 130 °C) was six times lower than that of die cast A380 (22 × 10−3 mm3/m at 93 °C and 28 × 10−3 mm3/m at 130 °C).

Based on the microstructural analysis, poor wear behaviour of die cast A380 compared to sand cast A356-T6 samples can be attributed to the presence of AlFeMnSi phases in the die cast A380 alloy microstructure. This was the region where several cracks originated. Sand cast A356-T6 has less Fe content than die cast A380. Fe in sand cast A356-T6 was in the shape of large needle-like β-Al5FeSi phase in its microstructure, which increased the hardness of the material and contributed to the wear resistance. In addition, the worn surface of sand cast A356-T6 produces a continuous oil residue layer, which protects the Al matrix and contributes to the higher wear resistance of sand cast A356-T6. Moreover, a lower wear resistance was observed at higher temperatures for both die cast A380 and sand cast A356-T6 alloys.

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