Effects Of Cu On Microstructure And Properties Of Al₂O₃/Mo₅Si₃ Composite By In-situ Synthesis

Mo₅Si₃ is considered to be a great potential candidates materials for high temperature structural. But, its strong room temperature brittleness and the insufficient strenth at high temperature which have hindered its practical application. Cu-Al₂O₃/ Mo₅Si₃ composites are synthesized from element MoO3, Cu, Mo, Si and Al powders by mechanical milling activation and hot-pressing sintering technology. Moreover we make the research of the microstructure, mechanical property and the corrosion mechanism of Cu-Al₂O₃/ Mo₅Si₃ silicides materials by XRD, OM, SEM and EDS etc. It has provided the theory basis for Mo₅Si₃ and Mo₅Si₃ composites in anti-corrosion material application.The main phase of the Cu-Al₂O₃/Mo₅Si₃ composites by experimental preparation are Cu,Al₂O₃ and Mo₅Si₃. Cu,Al₂O₃ and matrix Mo₅Si₃ have good syability. 20%Cu-20%Al₂O₃/Mo₅Si₃ composite has small crystal grain size, and the crystal grain sizes ofMo₅Si₃, Mo₅Si₃, Al₂O₃ and Cu are 73.6nm, 66.3nm, 64.8nm and 42.6nm, they all possessed nano-crystalline structure.The microstructure of hot-pressing sintering Cu-20%Al₂O₃/Mo₅Si₃ composites are uniform and compact. With the increase of Cu content, the composite microstructure refine, sintered density increase, microhardness decrease, fracture toughness increase and the strength first increase and then decrease. 15%Cu-20%Al₂O₃/Mo₅Si₃ composite has the best mechanical properties, the microhardness, compressive strength, flexural strength and fracture toughness are 1090HV, 2160MPa, 512MPa and 7.33MPa·m¹/2.In H₂SO₄ and HCl solution the corrosion resistance ability of Cu-Al₂O₃/Mo₅Si₃ composites is better than 304 stainless steel, with Cu content increase the corrosion resistance ability decrease, and corrosion weight loss of composite is lower 30 times than304 stainless steel. But in NaOH solution, the corrosion resistance ability is lower , which is similar with 304 stainless steel.The Al₂O₃ of composites has excellent resistance in HCl and H₂SO₄ solution, which can easily form Al₂O₃-SiO₂ compound passive film, hinder the matrix further corroded by solution. In NaOH solution, because NaOH of solution could dissolve SiO2 passive film in the surface of composites. It is hard to form effective protective layer, lead to the corrosion resistance being bad. In the Cu-Al₂O₃/Mo₅Si₃ composites, Cu is the easily corroded comonent, its chemical stability is bad, so that the corrosion resistance has decreased. In the other hand, Cu has increased the sintering property of composite and density, has decreased syomata and micro-defect, has effectively avioded local galvanic cell, thus the corrosion resistance has improved.