ã€ALUMINIUM NETWORK】ALUMINIUM MINE SOLID FURNACE EFFECTS OF AGEING EFFECTS The heat treatment of aluminum alloy castings is based on the selection of a certain heat treatment specification. The heating rate is controlled to rise to a certain temperature for a certain period of time at a certain speed to cool at a certain speed, and the alloy structure is changed. Its main purpose is to improve the mechanical properties of the alloy, enhance the corrosion resistance, improve the processing energy, and obtain dimensional stability. Age hardening of aluminum alloys The age hardening of aluminum alloys is a very complicated process. It depends not only on the composition and ageing process of the alloy, but also on the defects caused by alloy shrinkage in the production process, especially the number of vacancies and dislocations. Distribution and so on. It is currently believed that age hardening is the result of segregation of solute atoms to form a hardened zone. When the aluminum alloy solid melting furnace is heated by quenching, an vacancy is formed in the alloy. During quenching, these vacancies are too late to be removed due to cooling, and are “fixed†in the crystal. These vacancies in supersaturated solid solutions are mostly associated with solute atoms. Because the supersaturated solid solution is in an unstable state, it will inevitably shift to an equilibrium state. The presence of vacancies accelerates the diffusion rate of the solute atoms, thus accelerating the segregation of solute atoms. The size and number of hardened zones depends on the quenching temperature and quenching cooling rate. The higher the quenching temperature, the greater the concentration of vacancies, the greater the number of hardened zones and the reduced size of the hardened zone. The greater the cooling rate of quenching, the more vacancies fixed in the solid solution will help increase the number of hardened zones and reduce the size of hardened zones. A basic feature of precipitation hardened alloys is their equilibrium solubility as a function of temperature, ie, increasing solid solubility with increasing temperature, most heat treatable aluminum alloys meet this requirement. Factors affecting aging 1. Influence of the residence time from quenching to artificial aging Some aluminum alloys, such as Al-Mg-Si alloys, stay at room temperature and then undergo artificial aging. The strength index of the alloy does not reach a large value. Plasticity has risen. Such as ZL101 casting aluminum alloy, after quenching at room temperature for a day and then artificial aging, the strength limit is lower than the quenching immediately after the aging of 10 ~ 20Mpa, but the plasticity than the aging of the aluminum alloy has been improved. 2, the impact of alloy chemical composition whether an alloy can be enhanced by aging, first of all depends on the composition of the alloy element can dissolve in the solid solution and the degree of solid solubility with temperature changes. For example, the solid solubility of silicon and manganese in aluminum is relatively small and varies little with temperature. However, although magnesium and zinc have a greater solid solubility in aluminum-based solid solutions, the structure and matrix of the compounds formed with aluminum are similar. Little difference, little effect of strengthening. Therefore, binary aluminum-silicon, aluminum-manganese, aluminum-magnesium, and aluminum-zinc are usually not subjected to the aging strengthening treatment. And some binary alloys, such as aluminum-copper alloys, and ternary alloys or multiple alloys, such as aluminum-magnesium-silicon, aluminum-copper-magnesium-silicon alloys, etc., which have solubility and solid state phase transition in the heat treatment process, then It can be strengthened by heat treatment. 3. The influence of the solution treatment process of aluminum alloy is to obtain a good aging strengthening effect. Under the condition of no overheating, overheating and grain growth, the quenching heating temperature is higher and the holding time is longer, which is favorable for obtaining larger Supersaturated uniform solid solution. In addition, the second phase does not precipitate during the cooling process of the aluminum alloy solidification furnace, otherwise the precipitated phase will act as a nucleus during the subsequent aging treatment, causing local non-uniform precipitation and reducing the aging strengthening effect.
