Structure of AZ91 magnesium matrix alloy composite reinforced with graphite particles
Katarzyna N. Braszczyńska-Malik Czestochowa University of Technology, Institute of Materials Engineering, Armii Krajowej 19, 42-200 Czestochowa, Poland
Quarterly No. 3, 2008 pages 242-246
DOI:
keywords: magnesium matrix composite, graphite particles, structure
abstract The results of structure investigations of magnesium matrix composite reinforced with graphite particles have been presented. The AZ91 (Mg - 9 wt. % Al - 1 wt. % Zn - 0.5 wt. % Mn) alloy was used as a matrix. The investigated composite was reinforced with synthetic graphite particles with a maximum diameter of 10 m. A simple and non-expensive casting method involving mechanical mixing of liquid metal and the introduced ceramic particles under protective atmosphere was used to produce the investigated material. The obtained composite was characterized by uniform distribution of graphite particles within the matrix alloy. Graphite particles were observed both inside phase dendrites and interdendritical sides. In order to quantitative description of homogeneity of the structure, coefficient of variation of graphite particles number at the surface (fields method) was determined. Coefficient of variation was equal 0.266, testifying uniform distribution of graphite particles. Microstructure of composite was typical for gravity cast AZ91 magnesium alloy (solidified under non-equilibrium condition). solid solution, semi-divorced eutectic, discontinuous precipitates of phase (Al12Mg17) and Al8Mn5 intermetallic compound was observed in the composite microstructure, as a result of solidification process under non-equilibrium condition.