Effects of Graphite Particle Content and Holding Time on the Microstructure and Mechanical Properties of the Graphite/AZ91D Composite

Abstract

The effects of Grp (graphite particles) addition and holding time on the microstructure and mechanical properties of the Grp/AZ91D composite were investigated in this work. The results indicated that the distribution of Grp in the matrix was determined by the self-stabilizing mechanism and relationships between the solidifying interface and the particles. Due to the self-stabilizing mechanism, a small amount of Grp would uniformly distribute in the melt alloy, and as the amount of Grp increased, agglomeration would occur. Accordingly, the former would be engulfed by the solidifying interface and the latter would be pushed. With an increased holding time, Grp tended to agglomerate, due to the interfacial reaction that occurred, and as a result, the solidifying interface will push it. The Grp/AZ91D composite with the addition of 1.5 wt% Grp and a holding time of 15 min obtained grains 30.2 μm in size with a hardness of 89.07 HV, which was a decrease of 83.04% and increase of 35.06% compared to AZ91D, respectively.

Effects of Mold Temperature on the Microstructures and Tensile Properties of the Thixoforged Graphite/AZ91D Composite

“…Therefore, the interfacial bonding strength of the Grp/matrix is high. According to the selfstabilizing effect of Grp and the solidification theory [17], Grp distributes dispersively, which improves the properties of the Grp/AZ91D composite by dispersion strengthening [9]. At the same time, Al 4 C 3 can be formed during the remelting process, which is shown in Figure 12.…”

“…Commercial AZ91D ingots and self-made Grp/AZ91D pressed cakes were employed in this work. The detailed preparation process of those pressed cakes has been reported in the previous paper [9]. A quantity of the commercial AZ91D ingot (composition shown in Table 1) was melted in the furnace at 780 • C and refined with C 2 Cl 6 .…”

“…Shahin et al successfully prepared GNPs/Mg composites, where the addition of 0.30 wt.% could significantly improve the Young's modulus, tensile strength, and fracture strain (+131%, +49.5%, and +74.2%, respectively) [8]. Gao fabricated Grp/AZ91D composites by composite casting, which improved the hardness of the composites compared with the original alloy, and the distribution of Grp was determined by the self-stabilization mechanism [9]. Aatthisugan composites by stirring casting, which improved the strength, UTS, and wear-resistant properties of the composites [10].…”