Effect of Grain Refinement and SIMA Processing on Hot Tearing and Wear Characterisation of a Few Binary and Ternary Aluminium Base Alloys

摘要

A long freezing range Al-1Sn alloy is very prone to hot tearing. On increasing the amount of addition of Al-5Ti-1B grain refiner to an Al-1Sn alloy melt, the hot tearing tendency is reduced, but not completely eliminated. However, incorporation of a naturally immiscible low melting element like bismuth in an Al-1Sn alloy by SIMA processing reduces its hot tearing tendency significantly. Similarly lead or bismuth, normally immiscible in an Al-4Cu alloy, may also be introduced into such an alloy by SIMA technique in order to reduce its hot tearing tendency. The intergranular tear crack in a binary Al-1Sn alloy changes to a mixed intergranular and transgranular fracture mode in the SIMA processed Al-Sn binary or Al-Sn-Bi-ternary alloy. The wear characteristics of Al-Sn-Bi, Al-Cu-Pb and Al-Cu-Bi alloys have been investigated by the pin-on-disc wear test under three wear loads. The wear behaviour and friction coefficient of all these alloys are influenced by both work hardening as well as the lubricating effect of smeared bismuth or lead particles. Measurement of the micro-hardness of the α-Al matrix and friction coefficient of the pin samples along with SEM-EDX examination of the wear debris provide supporting evidence in favour of such complex influencing factors.