Effects of molten temperature on the morphologies of in situ Al3Zr and ZrB2 particles and wear properties of (Al3Zr+ZrB2)/Al composites

The (Al3Zr + ZrB2)/Al composites were fabricated from Al-K2ZrF6-KBF4 system by magneto chemistry in situ reaction technology. The effects of molten temperature on the morphologies of in situ Al3Zr and ZrB2 particles were investigated by SEM analysis and the dry sliding wear properties of the composites by wear tests. The XRD results show that the components of the as-prepared composites consist of Al3Zr, ZrB2 and alpha-Al phases. The SEM analysis indicates that the morphologies of Al3Zr are sensitive to the temperature of the aluminum molten. When the temperatures were 1123, 1173, 1223 and 1273 K, the morphologies of the Al3Zr with sphericity-shape, tetragon-shape, rod-shape and fiber-shape were observed, respectively; and the ones of ZrB2 showed no obvious diversity. Especially, when the temperature is 1273 K, the size of the Al3Zr with nano-fiber shape is about 180 nm in diameter. The dry sliding wear tests show that the wear weight loss of the S1, S2, S3 and S4 specimens shows no obvious difference with the sliding time of 15 min. With the increase of the sliding time, the wear weight loss increases. At a given sliding time, the wear weight loss of the specimens varies with the following order: S1 < S4 < S2 < S3. These are mainly due to the variation of the Al3Zr crystal morphology. (c) 2006 Elsevier B.V. All rights reserved.