Fabrication And Mechanical Properties Of CNTs/ZM5 Alloy Composites

Carbon nanotubes(CNTs)/ZM5 alloy composites were fabricated by stirring casting method with the effect procedure of the stirring technology studied. The mechanical properties of the composites which were under the state of as-cast, T4 solution treatment and high temperature were tested. The microstructure and fractographs were observed and analysised via scanning electron microscope(SEM) and energy spectrum analysis(EDS). Starting with the enhancement of the interface moistening property and dispersibility between CNTs and ZM5 alloy, the effect rules of room-temerature mechanical properties and elevated temperature properties of composites when enhancing the mass traction of CNTs addition were investigated systematically. At the same time, the change of microstructure and fractographs was investigated.The results showed that: CNTs could be added into the Mg molten alloy with stirring at the temperature near ZM5 alloy liquidoid. When under the state of as-cast, T4 solution treatment and high temperature, the addition of CNTs could significantly enhance the mechanical properties of composites, the rules of which were always enhancing, then reaching the maximum, and dropping at last. And also, Ni plating CNTs could reinforce the composites much better. Under the state of as-cast, when the addition of CNTs was 1.0wt%, the tensile strength and the elastic modulus reached th, maximum. When the addition of CNTs were 1.2wt% and 0.8wt%, the microhardness and the ductility reached the peak value respectively. After T4 solution treatment, the tensile strength and the ductility enhanced remarkably, but the elastic modulus and the microhardness declined. When the addition of CNTs were 1.0wt% and 0.8wt%, the maximum of the tensile strength and the ductility were 244MPa and 12.26% respectively. Under the state of high temperature, the tensile strength declined remarkably, and the ductility enhanced. When the addition of CNTs were 1.2wt%, the tensile strength and the ductility reached the maximum, which is 23.44% and 37.9% more than the value of the matrix respectively. The tensile strength of composites in 150℃temperature was much higher than the strength in 200℃temperature. CNTs could not only refine the grains of the composites, but also overlap the grains and bear the load of resistance to deformation. At the state of high temperature, CNTs could restrain the intenerating of the Al₁₂Mg₁₇ phase, and could effectively block the sliding of the grain-boundaries. The fracture mode of composites mainly consisted of the quasi-cleavage crack, the dimple and the tear edge, which showed the feature of gliding fracture. Compared with the state of as-cast, the dimple and the tear edge in fracture were much wider and deeper when in the state of T4 solution treatment and high temperature. So it is showed that it had much higher ductility. CNTs dispersed homogeneously in the matrix, and formed more strong interface bonding. In the fracture, CNTs were mainly in the state of push-out and break-off, and overlapped the tear edge.