Behaviour of MgZn6-SiCp composites during compression test
Katarzyna N. Braszczyńska-Malik, Przemysław Chmielowiec Politechnika Częstochowska, Instytut Inżynierii Materiałowej, al. Armii Krajowej 19, 42-200 Częstochowa
Quarterly No. 1, 2005 pages 99-104
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abstract The results of mechanical testing of magnesium matrix composites under compression have been presented. The Mg - 6 wt.% Zn alloy was used as a composite matrix. The investigated composites were reinforced with different amount of silicon carbide particles, namely 10, 20 and 30 wt.% of SiCp. A simply and non-expensive casting method involving mechanical mixing of liquid metal and the introduced particles under the protective atmosphere was used to obtain the investigated materials. The resulted composites were characterized by uniform distribution of silicon carbide particles within the matrix alloy. Moreover, the components did not reveal creation of a reaction layers at the matrix/particles interfaces (Fig. 1). The matrix alloy was composed of a solid solution of zinc in magnesium (α phase) and a eutectic of α+β phases located in interdendritic spaces. The yield strength value of composite reinforced with 10 wt.% of SiC particles was 110 MPa. The ultimate compressive strength of the composite was equaled to 344 MPa, what was shown in Figure 2. Increase the weight fraction of the reinforced phase caused a decrease in the plastic strain carried by the composites. However, it increased the values of the mechanical parameters measured during compression tests. Both of the parameters (the proof stress and the ultimate compressive strength) increased with the weight fraction of SiC particles (Fig. 3). In this paper the results of examination of the cracking path of the composites have been also described. The main cracking path followed the direction of the maximum shearing stress (Figs 4 and 5). The cracks in the tested composites, that arose during compression, propagated in the magnesium alloy matrix avoiding the interfaces between the SiC particles and matrix. This proves the strong connection between the metal matrix and the reinforcing phase. The performed analyses of the composite microstructure after compression tests did not reveal any cracks propagation at the matrix/particles interfaces or from the SiC particles to matrix. Key words: metal matrix composites, ceramic particles, compression test