Internal Friction and Young's Modulus of Some Rapidly Solidified Al-Si Alloys

(Received 27 December 1995, revised 19 August 1996, accepted 30 September 1996)

Abstract
Al-16 Si, Al-12.5 Si-1 Ni and Al-12.5 Si-1 Mg ribbons were prepared by melt spinning. Internal friction was measured in the forced flexural and torsional decay modes. Internal friction increases slowly with the increase in temperature up to a certain temperature, above which the rate of increase is higher. This behaviour is common in all the three alloys, and is more pronounced in the torsional vibration mode than in the flexural vibration mode. The temperatures at which the internal friction shows a significant change in slope are 573, 518 and 554 K in the flexural mode and 456, 496 and 529 K in the torsional mode for Al-l6 Si, Al-Si-Ni and Al-Si-Mg respectively. From the measurement of resonance frequency with temperature, Young's modulus was calculated. The room temperature values are 3.6, 2.1 and N m ^-2 for Al-l6 Si, Al-Si-Ni and Al-Si-Mg respectively. These values are in fair agreement with the values deduced from the tensile tests. The variation of Young's modulus with temperature obeys the expression given by Andrews. The temperatures at which in Y versus T(K) changes its value are about 100 degrees above 0.5  on the average for the three alloys. A discussion on the relation between the behaviour of internal friction and Young's modulus with temperatures is given.