The TTP Curve Of High Silicon Wrought Aluminum Alloy With Magnesium Content And On-line Quenching

High silicon wrought aluminum alloy with magnesium content which is developed by Northeastern University is a new kind of material which has excellent properties such as high specific strength, corrosion resistance, low density and strong wearability, having broad application prospect in military and civil field. The strength of this kind of material is better than6xxx series alloys and the plasticity is as good as6xxx series alloys. However, the study of this kind of material’s heat treatment is still at its starting stage and the research of on-line quenching which can cost saving has not started yet at home and abroad.This paper aimed to study the quenching sensitivity and TTP curve to get the critical cooling rate. On that basis, the research focus on the influence of the cold effect on the solution temperature. The results are shown as below:1.When Al-12.7Si-0.7Mg alloy which is in completely solution state is isothermal holding between230℃and525℃, the relationship between hardness and isothermal time meets Boltzmann equation:y=A2+(A1-A2)/(1+exp((t-A3)/A4)). The relationship between electrical conductivity and isothermal time meets Boltzmann equation as well.2.The fitted TTP curve of AI-12.7Si-0.7Mg alloy is shown below: 3.The critical temperature range of AI-12.7Si-0.7Mg alloy is between350℃and450℃. When Al-12.7Si-0.7Mg alloy is quenched in this critical temperature range, the critical cooling rate must be greater than289℃/s.4. When Al-12.7Si-0.7Mg is on-line quenched, the cooling temperature distribution and cooling speed change with the distance from spay quenching spot, the cooling rate is faster when the distance increase. When the distance from spay quenching spot is more than20mm, the cooling speed is less than289℃/s, and the distance from spay quenching spot is less than45mm, the cooling speed is more than12.8℃/s which is the critical cooling rate of the TTP curve of90%hardness.