Fabrication,Microstructure Characterization And Properties Of NiTi Fiber-reinforced Ti-Mg Laminate Composite

With the rapid development of aerospace,automotive and other fields,single-component metals or alloys can no longer meet the requirements of their performance.Therefore,the development of metal matrix composites has become the focus of current research.Mg alloy has great application prospect owing to its low density,high specific strength,high specific stiffness and good damping performance,but the lower absolute strength restricts its application rage.Ti alloys have excellent properties such as high strength,however,it is subject to certain limitations due to the high density.NiTi shape memory alloy not only has shape memory effect,and pseudoelasticity,but also a smart material with high damping capacity.Therefore,combining the advantages of Mg and Ti alloys and introducing NiTi fibers into the composite,the structure-function integrated metal matrix composite with high strength and high damping can be prepared.In this paper,Ti,Mg alloy plate,continuous NiTi fiber and industrial pure Al foil?Ti/Mg bonding layer?were used as raw materials to prepare NiTi fiber reinforced Ti-Mg laminate composites with“Ti-Mg?NiTi?Mg-Ti”structure by vacuum hot-press sintering.The SEM and EDS were used to characterize the composites prepared at different sintering temperatures.The effect of holding temperature on the sintering quality was investigated and the optimum sintering temperature was determined to be 545°C.The atomic diffusion and reaction at the interface of the composite were studied.The results showed that the Al foil at the Ti/Mg joint disappeared during the preparation process,Mg₁₇Al₁₂,Al₈Mn₅,and Al₁₃Fe₄ particles were formed on the Mg side,meanwhile,a¹?m Al diffusion layer was observed on the Ti side of the interface.After the NiTi fiber was introduced,the fiber was uniformly distributed in the middle of the Mg layer,and an Al₃Ni₂ phase was formed at the NiTi/Mg interface.The properties of the composites was tested,and the effects of the introduction of NiTi fibers and their distribution on the physical,mechanical,and damping properties of the Ti-Mg laminate composites were investigated.The density of the composite measured by the displacement method was between 2.3-2.4 g/cm³.The micro-hardness tester was used to test the hardnes and the results showed that the micro-hardness of the composites with and without NiTi fiber was distributed in a periodic manner perpendicular to the stacking direction.The universal testing machine was used for compression and tensile tests,the compression and tensile mechanical properties of Ti-Mg laminate composites after introducing NiTi fibers and changing the fiber layout were compared.The results showed that the compressive strength of the composite parallel to stacking directions are higher than those perpendicular to the stacking direction,which presented anisotropic characteristics.The compressive strength and strain-to-failure of the Ti-Mg laminate composites were significantly improved after the fiber was introduced,and the failure strain of the composite with uni-directional arranged fibers was higher than that of the orthogonally arranged one.After the fiber was introduced,the tensile strength and yield strength of the composites increased by 12.6%and 24.3%,respectively,and the tensile strength and yield strength of the composite with orthogonally arraged fibers were higher than that of the uni-directional arranged one,reaching 572.2 MPa and 528.6 MPa,respectively.The Q800DMA dynamic mechanical thermal analyzer was used to test the damping of the composite,and the effect of NiTi fiber on the damping performance of the composite was investigated.It was found that the introduction of NiTi fiber increased the storage modulus,loss modulus and damping factor of the composites,and the overall damping performance of the composites was enhanced.