半固态铸造A356铝合金冷却斜槽工艺参数的建模与优化

摘要

使用冷却斜槽工艺加工半固态 A356铝合金。运用 D-实验优化设计(DODE)设计实验并分析实验结果。采用软件抽取38个随机实验。冷却斜板长度为100、300、500 mm，斜板的斜角为30°、45°、60°，浇铸温度为660、680和700°C。将半固态铝合金浇铸到铜质冷却斜板上，然后倾入到钢模中成型。铸造完成之后，在温度590°C下，对部分样品进行5、8、12 min重熔处理。研究这些因素对初生α(Al)晶体圆整度的影响，并使用DODE进行参数优化处理。结果表明，传统铸造A356合金的初生α(Al)相为枝晶，而冷却斜槽铸造的为非枝晶。重熔后再经过冷却斜槽处理的样品呈现出球状结构。最优的浇铸温度、冷却板长度、斜角和保温时间分别为660°C、360 mm、48°和9 min。在最优条件下，得到初生晶体的圆整度为0.91。所建立的模型的相关系数为0.9860。%Semi-solid processing (SSP) of A356 aluminum alloy was discussed via cooling slope (CS) method. The D-optimal design of experiment (DODE) was employed for experimental design and analysis of results. 38 random experiments obtained by software were carried out. In experimental stage, the molten aluminum alloy was poured on an inclined plate with different lengths of 100, 300 and 500 mm set at 30°, 45° and 60° of slope angles respectively. Three different pouring temperatures of 660, 680 and 700 °C were also used. After the casting process, the partial re-melting treatment was carried out at 590 °C for different isothermal time of 5, 8 or 12 min. The combined effect of these factors on globularity of the primary α(Al) crystals was investigated and optimized using DODE. The results indicated that the primary dendritic phase in the conventionally cast A356 alloy was transformed into a non-dendritic one in ingots cast over a cooling plate. The CS processed samples exhibited a globular structure only after re-heating to semi-solid region. The optimum values of pouring temperature, cooling length, slope angle and isothermal holding time were found to be 660 °C, 360 mm, 48°, and 9 min, respectively. In this case, the globularity of primary crystals was obtained, about 0.91. The obtained model is highly significant with a correlation coefficient of 0.9860.