Effect of Al–Nb–B2O3–CuO system reaction products on microstructure and wear resistance of A356 alloy

The aim of present work is study the effcet of Al-Nb-B2O3-CuO system reaction products on microstructure and properties of A356 alloy. B2O3 powder, Al powder, CuO powder and Nb powder were used as raw materials to form Al–Nb–B2O3–CuO reaction system, and A356 alloy was refined by in situ reaction and near-liquidus casting. The size, phase, morphology and distribution of in situ reaction products were observed and analysed by optical microscope, x-ray diffractometer, scanning electron microscope and transmission electron microscope. The products of the Al–Nb–B2O3–CuO reaction system are mainly Al3Nb, NbB2 and Al2O3. The ratio of the prefabricated block is 8:1:1:2 . When the prefabricated block was added at 2.5 wt%, the particle size of NbB2, Al3Nb and Al2O3 is 0.5–1 μm. The microstructure of A356 alloy is fine and uniform. The average grain size is refined to less than 20 μm. Compared with untreated A356 alloy, the wear rate is reduced from 2.091% to 0.882%, and the average hardness of the alloy is increased from 41.3HRC to 58.2HRC.