Mechanical properties of Al-60 Pct SiC p composites alloyed with Mg
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5/24/04
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Mechanical Properties of Al-60 Pct SiCp Composites Alloyed with Mg ˇ LU ˙ H. AHLATCI, E. CANDAN, and H. Ç IMENOG In the present work, the effect of an Mg addition on the mechanical properties of the Al-60 vol pct SiCp composites were investigated by uniaxial compression, three-point bending, impact and wear tests (composite-metal and composite-abrasive types). The composites were produced by the pressure-infiltration technique. The composition of the Al matrix was varied between 0 and 8 pct Mg. The mean diameter of the SiC particles was 23 m. Upon addition of Mg, Mg2Si precipitated in the matrix and the amount of the porosity dramatically decreased. Mg-alloyed-matrix composites exhibited higher strength, lower toughness, and higher wear resistance than pure-Al-matrix composites. During composite-metal wear testing, wear progressed in two sequential periods (running-in and steady state). Weight loss during wear testing decreased with increasing Mg content of the matrix. The degree of improvement of abrasive resistance depended on the abrasive-grain size. Above 200 °C, the composite-abrasive wear resistance decreased with increasing test temperature for all materials.
I. INTRODUCTION
DISCONTINUOUSLY reinforced aluminum matrix composites are one of the advanced engineering materials that have been developed for weight-critical applications in the aerospace and, more recently, in the automotive industries, due to their excellent combination of high specific strength and improved wear resistance.[1,2,3] The wear behavior of composites is affected by various intrinsic parameters, such as type,[4] size,[4–11] and volume fraction[4,8–10,12–22] of the reinforcement. Garcia-Cordovilla et al.[4] investigated the effect of types of reinforcing materials, including Al2O3 and SiC particles, on the wear behavior of Al matrix composites and observed improved wear resistance with SiC particles. Previously, the effect of particle size on the wear behavior of Al matrix composites has been reported to depend on wear conditions, i.e., load, sliding velocity, and abrasivegrain size.[4–11] In most cases, the wear resistance increased with increasing size of reinforcement.[5–10] However, it has not been improved (in some cases it was even weakened) when the wear took place by delamination and/or particlefracture mechanisms.[11] In most studies,[4,8–10,12–16,18,21,22] the wear resistance of composites has been improved by increasing the volume fraction of the reinforcement. Al matrix composites exhibited similar tendencies, depending on extrinsic parameters such as the load,[10,12,16,18,23–27] type of counterface,[13,18,28] size of abrasive grains,[5,9–11,13,18,23,27,28] and temperature.[29–34] With increasing load and/or abrasive-grain size, the wear rate increases. High-temperature wear tests revealed that the wear rate is maintained constant up to a critical temperature.[29–34] The transition from mild to severe wear has been observed at a critical temperature under a constant load,[29–34] or vice versa.[31
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