The Effect Of Thermal Cycling On Damping Capacity Of Aluminum Matrix Composites Reinforced With Sn-Bi Coated Al₁₈B₄O₃₃ Whisker

Alumina borate whisker (Ali8B4O33w)-reinforced aluminum matrix composites were the object of investigation. SnO2、Bi2O3and SnO2·Bi2O3were coated on the surface of whiskers by using chemical method. Then interfacial phase with a low melting point Sn、Bi and SnBi alloy were introduced into the surface of whisker by squeeze casting. The mass ratio between coating and whisker was1:10and the volume fraction of whisker in the composites was20%. Organizations and the phase change of composites before and after thermal cycling were studied by XRD. Microstructures of composites were observed by means of TEM. The damping test of composites were tested by DMA. The room-temperature tensile was tested. The effect of the temperature and cycles of thermal treatment on damping and mechanical properties of composites was analyzed.The result of XRD indicated there was no interface reaction during the thermal cycling. TEM showed that high temperature cycling trentment made the form and distribution of interfacial phase with a low melting metal and the dislocation state in the vicinity of the interface changed.The investigation of the temperature dependent damping capacity showed that the damping capacity was influenced of thermal cycling treatment, especially under the high temperature cycling. The damping of background improved and P2peak shifted to low temperature and corresponding activation energy declined with the increasing of the cycles of thermal treatmentThe investigation of the strain amplitude dependent damping capacity showed that thermal cycling affected room temperature damping weakly. The damping increased at low strain amplitude after thermal cycling. At high strain amplitude showed the opposite law:damping declined with the decreasing of times of cycles which was related to the G-L dislocation theory and interface micro-slip.The room-temperature tensile tests of single coated composites implied that the yield strength of the composites after thermal cycling increased. Tensile strength increased weakly with the increasing of times of cycles under low-temperature cycling. At high temperature treatment interface bonding states of the SnO2coated composites became stronger due to the small size of the Sn. The elongation of the Bi2O3coated composites decreased significantly due to the reducement of the interface bonding states.