Research On Fabrication And Properties Of CNTs/AZ91D Magnesium Matrix Composites

CNTs/AZ91D magnesium matrix composites were prepared by powdermetallurgy, and then the composites had the solution treatment after fabricated by hotextrusion.At the same time,the research on the related technology of preparingmagnesium matrix composites by powder injection molding was conducted. TheCNTs and composites were evaluated with Raman spectroscopy, infraredspectroscopy, X-ray diffractometer (XRD), energy dispersive spectrometer(EDS) andscanning electron microscope(SEM). The influence of CNTs treated via differenttechnology (ball milled and surface coated MgO) and its addition content oncomposites have been investigated; the effects of solution treatment onmicro-structure and mechanical properties of composites have been studied; theimpact of CNTs on the wear resistance of hot-extruded composites have been tested;in addition,the impact of binder systems and different technology of debinding andsintering on experiment results have been studied.The research results show that: the best choices for CNTs dispersed well anddamaged less are ball milled by the parameters of200rpm and4h. CNTs wereuniformly coated MgO by chemical reaction and the defect level was decreased.Adding CNTs to AZ91D magnesium alloy can significantly improved mechanicalproperties of composites, when the addition content was3.0wt%, the value of tensilestress, elongation and micro-hardness of hot-extruded composites reached themaximum which were248.33MPa,13.2%and127.14HV, increased by36.83%,46.67%and18.97%, in addition, the solution treatment and hot extrusioncomposites shared the same rule. The strengthening result (including tensile stressand micro-hardness) was obvious for CNTs coated MgO, however, the elongationdecreased. For the extrusion composite, the fracture mode of matrix alloy mainlyconsist of the cleavage step, the dimple, little tear edge and river pattern, which showsthe characteristics of hybrid fracture. Adding1wt%CNTs, the fracture mode ofcomposites mainly consist of the dimple and tear edge, and the amount of dimpleincreased obviously, which shows the characteristics of ductile fracture. The wear resistance of composites improved with the adding of CNTs, the wear resistance ofcomposites has the direct ratio with the addition of CNTs. The weight loss ofnaphthalene based binder was higher than the wax based binder when prepared themagnesium based composites by powder injection molding, the study shows that theparameters influenced the results goes to three aspects, which are the oxidation ofmagnesium powder, the mass loss rate of binder and the particle size of magnesiumpowder.