In-situ synthesized (Al_3Zr+Al_2O_3)_p /A356 composites by direct melt reaction in Al-Zr-O system

1　INTRODUCTIONRecently ,muchattentionhasbeen paidtothedevelopmentofeffectivefabricationprocessesforpar ticulatereinforcedmetalmatrixcomposites (PRMM Cs) 13] .However,metalmatricesreinforcedwithparticlesformedinsituareanemerginggroupofdis continuouslyreinforcedcompositesthathavedistinctadvantagesovertheconventionalcomposites4 ,5] .Inthein situfabricationprocess ,thespontaneousreac tionbetweenthereactantsisutilizedtosynthesizethereinforcementsinthemetalmatrix .Especially ,thedirectmelt…

In-situ synthesized (Al3Zr+Al2O3)p/A356 composites by direct melt reaction in Al-Zr-O system

A novel in-situ reaction system Al-Zr-O was developed. In situ Al3Zr and Al2O3 particulate reinforced A356 alloy matrix composites have been fabricated by direct melt reaction method. The results show that the maximum sizes of Al3Zr and Al2O3 particulates synthesized in the system ZrOCl2-A356 are 1 μm and 3 μm respectively, and they are well distributed in the matrix. The investigation shows that the Al3Zr crystal is in the shape of polyhedron and rectangle. There is a faceted growth phenomenon on Al3Zr crystal surface. It is firstly found that the Al3Zr crystal grows in the mechanism of twinning. The twinning plane is (1 1 4), and the twinning direction is 2 2 1]. The crystal morphology of in-situ α-Al2O3 particulate is rectangle or sphere. Furthermore, (Al3Zr+Al2O3)p/A356 composites have not only higher tensile strength at room temperature (376.2 MPa) but also higher yield strength (319.4 MPa) and higher tensile strength at elevated temperature (200 ℃) than those of the A356 alloy. The dry sliding wear test shows that the wear resistance of the (Al3Zr+Al2O3)p/A356 composites is greatly enhanced with increasing particulate volume fraction.