Effect of different aging treatment on microstructure and properties of Cu-3Si-2Ni alloy was studied by measurements at room temperature tensile properties, XRD and fracture analysis. The results show that the strengthening phase particles are precipitated along grain boundaries and inside grains after aging treatment of Cu-3Si-2Ni alloy, which benefits the yield and tensile strength at room temperature except for the elongation. In addition, the fracture surface shows that mixed ductile and brittle features, while as-soluted Cu-3Si-2Ni alloy presents the typical ductile fracture. The appropriate aging treatment is 450°C×2h after care experiments in this paper.

In order to study thecharacteristics of this new type of quenching process that is atomized waterspray quenching, this article analyzes the influence factors of atomized waterspray quenching based on the newly developed aerosol spray quenching experimentdevice. Based on 2 method, the two factors of water flow and nitrogen pressureare controllable, we analyzed the influences of the two factors of nitrogenpressure and water flow to the quenching cooling time. This paper induces andanalyses the experiment results and numerical calculation results[1]. The conclusions are: water flow is the main factor ofaffecting the quenching rate, the interaction of the nitrogen pressure andwater flow is significant: when the nitrogen pressure is low ,the water flow ishigh, the quenching cooling rate is guaranteed.

In order to analyses the effect of structure of collection loop on two-phase flow field in quenching furnace, the complex flow field in furnace for mixture of Nitrogen and spray water ejecting quenching under normal pressure and high velocity is numerically simulated with Mixture model of two-phase flow by CFD software FLUENT. Different inlet velocity, different volume percent of spray water, different velocity differences between Nitrogen and spray water, and different angle and dimension of collection loop affected on outlet velocity are analyzed. The research results show that the flow field is really complex, and around inner and outside canister and collection loop back flow exists. The angle of collection loop has less effect on outlet velocity, and the inner diameter of collection loop has more effect on outlet velocity. The simulation results show that the furnace can accelerate the flow of quenching media, which can cool specimen quickly.

During mixture of Nitrogen and spray water ejecting quenching under normal pressure and high velocity, the liquid film that is formed on the surface of specimen to reduce the heat transfer between specimen and quenching media is removed on the one hand; on the other hand, the heat transfer performance of the mixture exceeds that of pure Nitrogen. Because the surface heat transfer coefficient is difficult to measure, according the cooling curve of surface and centre of specimen measured experimentally, the law of surface heat transfer coefficient and specimen temperature is calculated by nonlinear estimate methods and finite difference method based on inverse heat transfer method. The results show that the cooling performance of mixture of Nitrogen and spray water is as well as that of water or oil. During quenching, the surface heat transfer coefficient increases rapidly at begin, and at temperature of 170 °C, the surface heat transfer coefficient decreases. During martensite phase transformation, the latent heat is used to increase drive force of phase transformation and to overcome resistance of phase transformation, thus the martensite phase transformation can fulfill.

A finite element model of not wholly quenched steel fatigue specimen is established. Hardness value of some distance to work piece surface are assumed different and cyclic strength coefficients of different zones are different, both is assumed to be proportional to hardness value. Elasto-plastic finite element analysis was carried out for this model. According to the stress-strain distribution on transverse section, the effect of not wholly quenched on fatigue crack initiation life is analyzed.