The Research On Microstructure And Properties Of Multi-aluminum Bronze

Recently, dies made of high aluminum bronze had been imported in order to replace ferrous matrix alloy dies, such as 35CrMo. This new kind of Aluminum bronze, which have the properties of high strength, wear resistance and low friction coefficient, is the excellent material for precise steel stretching and squeezing dies. Contrast experiments were performed on its preparation and heat-treatment hardening process, and this new kind of Cu-wt%14Al-X bronze were domestically produced. And the results show that:1. Jointly-loading stuffs single melting way, which converses the traditions of one-melting way's high temperature melt first and the second-melting way's middle-alloy processes, avoids the oxidation and inspiration coursed by the high aluminum content and adding low melting temperature Al to molten melt of high melting temperature Fe, Co, Ni and Mn etc. Companying with speedy melting and timely pouring, eligible molten alloy and defects free castings were acquired.2. Microstructures of Cu-14Al-X alloy were analyzed by Optical Microscopy, X-Ray Diffraction Spectrum, Electron Micro-probe Analysis, Scanning Electronic Microscopy, Electrolyte and Deep erosion. Results show thatα,β,κandγ2 phase are the main phases in the alloy, a lot of Cobalt are concentrated in the k phase, and heat treatment just changes the relatively quantity of difference phases. After heat treated, more Fe distributed in the alloy's matrix makes a higher micro-hardness, although a lower relatively quantity ofκphase company to the as-cast state.3. As-cast microstructure of the high aluminum bronze areα+β+κ+γ2 phases, with lopsided structure, supersaturation and deflection precipitation(偏析,可能不对) in it, and composition and impurity on grain boundary. Size of grain, content of a phase, distributing ofγ2 phase and the size and quantity of k phase causes the as-cast alloy a difference mechanical property, as a result, high-hardness and low ductility comes from big size grains, low content ofαphase, on grain boundary distributing of big sizeγ2 phase. Theκphase has a dispersion strengthen effect to the alloy.4. After low temperature anneal, the matrix of the alloy is stillα,β,κandγ2 phase, which causes the alloy a high hardness and lower ductility. During the serial anneal with a different temperature and seem time, the bronze possess the best overall mechanical properties. It can be conclude from the quench followed by ageing experiments that the grain will grow up,κandγ2 phase will dissolute into the matrix with the increasing of quenching temperature, and the strengthening phase will separate out completely, even the eutectoid phase, which cause a low mechanical properties. The microstructure,κandγ2 phase uniformly distributed inβphase would be obtained by quenched (920℃×2h) followed by (580℃×5h) aged, consequently with the best overall mechanical properties...