Thermal expansion and dimensional stability of unidirectional andorthogonal fabric M40/AZ91D composites

来源期刊：中国有色金属学报(英文版)2010年第1期

论文作者：宋美慧 武高辉 陈国钦 杨文澍

文章页码：47 - 53

Key words：composites; coefficient of thermal expansion; dimensional stability; thermal cycles

Abstract: Unidirectional (60%, volume fraction) and orthogonal (50%, volume fraction) M40 graphite fibre reinforced AZ91D magnesium alloy matrix composites were fabricated by pressure infiltration method. The coefficients of thermal expansion (in the temperature range of 20-350 ℃) and dimensional stability (in the temperature range of 20-150 ℃) of the composites and the corresponding AZ91D magnesium alloy matrix were measured. The results show that coefficients of thermal expansion of the composites in longitudinal direction decrease with elevating temperature. The coefficients of thermal expansion (CTE) for unidirectional M40/AZ91D composites and orthogonal M40/AZ91D composites are 1.24×10^-6 ℃^-1 and 5.71×10^-6 ℃^-1 at 20 ℃, and 0.85×10^-6 ℃^-1 and 2.75×10^-6 ℃^-1 at 350 ℃, respectively, much lower than those of the AZ91D alloy matrix. Thermal cycling testing demonstrates that the thermal stress plays an important role on residual deformation. Thus, a better dimensional stability is obtained for the AZ91D magnesium alloy matrix composites. More extreme strain hysteresis and residual plastic deformation are observed in orthogonally fabric M40 reinforced AZ91D composite, but its net residual strain after each cycle is similar to that of the unidirectional M40/AZ91D composite.