铝合金搅拌摩擦焊后人工时效力学性能数值模拟

摘要

采用KWN模型构建搅拌摩擦焊接中Al-Mg-Si系铝合金沉淀相演化计算模型,通过将屈服强度分为晶粒大小、固溶相和析出相三部分贡献,可以计算平板搅拌摩擦焊后的屈服强度和硬度.进一步研究不同焊后人工时效条件下,焊接平板力学性能变化的机理.结果表明:更长的焊后保温时间有利于搅拌区力学性能的回复;较高的保温温度有利于搅拌区力学性能的快速回复,但是当温度高于200 ℃时,长时间保温会使母材软化,不利于力学性能回复;通过焊后人工时效不能明显改善热影响区的力学性能.%KWN model was used to establish the precipitation evolution model of friction stir welding of Al-Mg-Si alloy.The yield strength was divided into three parts: the contribution from grain size, the contribution from solid solution and the contribution from the precipitations.Based on this model, the yield strength and hardness of friction stir weld was predicted.The effect of post weld artificial ageing on mechanical properties of friction stir weld was further investigated.The results indicate that longer holding time can be beneficial to the recovery of mechanical properties in the stirring zone.Higher temperature can lead to quick recovery of mechanical properties in the stirring zone, but when the holding temperature is higher than 200 ℃, longer holding time can lead the base metal softened, which is harmful to the service of friction stir welds.The mechanical property in the heat affected zone cannot be improved by post weld artificial ageing.