Plastic Properties of a Mg-Al-Ca Alloy Reinforced with Short Saffil Fibers
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MAGNESIUM alloys reinforced with short ceramic fibers exploit a comparatively high stiffness of ceramic fibers and plasticity of metallic matrix.[1] Such materials have unique and desirable mechanical and thermal properties.[2] Metal matrix composites (MMCs) have higher moduli,[3,4] higher strength,[5,6] more enhanced fatigue properties,[7] and lower thermal expansion[8] than their metallic counterparts. On the other hand, plasticity of MMCs is lower especially at lower temperatures. MMC can be processed with conventional techniques; but in some cases, they are manufactured by relatively complicated and expensive methods.[9] The potential to use the materials’ architecture methods for tailoring of physical and mechanical properties of MMC is highly attractive. While, during straining, the reinforcing phase is deformed only elastically, plastic deformation occurs in the matrix. The deformation processes in the matrix are influenced by the presence of the reinforcing phase (fibers or particles). Many attempts have been made to find the relationship between mechanical properties and possible effects of the reinforcing phase. fibers or particles may influence not only the microstructure and dislocation substructure of the MMCs, but also the deformation processes themselves.[10–13] The main objective of this study is to investigate the deformation behavior of an AX41 magnesium alloy reinforced by short Saffil fibers and to estimate possible deformation mechanisms operating in the matrix during plastic deformation.
ZUZANKA TROJANOVA´ and PAVEL LUKA´Cˇ, Professors, KRISTIA´N MA´THIS and MILOSˇ JANECˇEK, Associate Professors, and GERGELY FARKAS, Doctoral Student are with the Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu str. 5, 121 16 Praha 2, Czech Republic. Contact e-mail: [email protected]ff.cuni.cz Manuscript submitted March 13, 2013. Article published online November 23, 2013 METALLURGICAL AND MATERIALS TRANSACTIONS A
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EXPERIMENTAL
Magnesium alloy AX41 (4 wt pct Al, 1 wt pct Ca, balance Mg) was reinforced with 13 vol pct of short Al2O3 (Saffil) fibers. Composites were prepared by the squeeze casting technology. The preforms consisting of Al2O3 short fibers showing a planar isotropic fiber distribution and a binder system (containing Al2O3 and starch) were preheated to ~1273 K (1000 C) and then inserted into a preheated die [573 K to 633 K (300 C to 360 C)]. Preforms were infiltrated by the liquid alloy using two-stage application of the pressure. Composites were not thermally treated. The mean Saffil fiber length and fiber diameter measured after squeeze casting were 78 and about 3 lm, respectively. Samples for deformation tests were cut from the bulk composite so that the fiber’s plane was parallel to the stress axis. Compression tests were carried out in an INSTRON 1186 universal testing machine with the displacement control at a nominal strain rate of 8.3 9 105 s1 in a wide temperature range from room temperature (RT) to 573 K (300 C). The temperature in the f
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