Investigation on mechanical and wear properties of strontium modified aluminium-silicon alloy

Abstract

Wear has deleterious impact on technological use of material and its economy. It was estimated that the direct cost of friction and wear can account nearly 10% of the gross national product (GNP) in many industrial countries, thus research on wear is inevitably vital for developing country like Malaysia. Aluminium-silicon eutectic alloy has been undertaken as a wear testing material in this study due to its best overall balance of properties that are well suited for wear resistance components in the automotive industry. Its low expansion, low density and high resistance to corrosion at ambient temperature characteristics made this alloy an excellent candidate for automotive pistons. Moreover, the addition of small amounts of strontium to the molten aluminium-silicon alloy could produce complete modification of the solidification process. The modification treatment produces remarkable refinement of the eutectic silicon phase and improves the mechanical properties of the alloy. Wear testing has been conducted with a pin-on-disc type wear testing apparatus under lubricant sliding. The test variables were rotational speed, load and sliding distance. In addition to that, attention has been paid to the effects of heat treatment on the strontium modified alloy. The extent of wear damage has been estimated by means of weight loss technique. Possible wear mechanisms of the damaged samples have been investigated with the aid of scanning electron microscope (SEM). From the present investigation, it was found that a considerable improvement in mechanical properties such as an increase in hardness and strength was associated with the resulting structural changes. This lead to an improved tribological performance compared to its unmodified counterparts. Transitional behaviour between fatigue surface, adhesive, abrasive and corrosive wear were exhibited from the worn surfaces. Overall, modified heat treated samples had shown better performance in both mechanical and wear properties.