Wettability of Flame-Resistant Magnesium Alloy on Graphite Sheet and Preparation of VGCF/ Magnesium Alloy Composites

Abstract

Mg-5wt%Al-3wt%Ca (Mg-5Al-3Ca) alloy is the representative flame resistant magnesium alloy, which is developing to use the parts of transformation equipment such as train, automobile and airplane. In order to improve the mechanical properties of this alloy, the development of the composite with carbon fiber is one of the suitable solution. In order to obtain the high performance metal matrix composites, the estimation of the wettability between the reinforcement and alloy is important because of the estimation of the interface strength between alloy and carbon fiber, and the choice of composite preparation process. In this study, the wettability between the alloy and the graphite sheet with (002) oriented surface structure was estimated. The wettability at 573 K in vacuum is about 120 degrees, which is low wettability. In order to improve the wettability, Ni was coated on graphite sheet. By using Ni coating with 3.7 μm in thickness, the wettability was improved to 90 degrees. Then, 0.5 wt. % vapor grown carbon fiber (VGCF) dispersed Mg-5Al-3Ca alloy composites was fabricated by stir casting process. Ni was coated on welldispersed VGCF by electroless Ni plating. VGCF was dispersed uniformly without aggregation in matrix, and microstructure of matrix was very similar with the conventional casted Mg-5Al-3Ca alloy.