高强超声场对Al-Si活塞合金凝固特性及显微组织的影响  

Solidification and Microstructure of Al-Si Piston Alloy by Melt Ultrasonic Treatment

作　　者：郭永春[1] 董雄博 李建平[1] 夏峰[1] 杨伟[1] 白亚平[1] Guo Yongchun;Dong Xiongbo;Li Jianping;Xia Feng;Yang Wei;Bai Yaping(School of Materials and Chemical Engineering, Xi ＇an Technological University, Xi ＇an 710021, China)

机构地区：[1]西安工业大学材料与化工学院

出　　处：《稀有金属》2018年第7期713-721,共9页Chinese Journal of Rare Metals

基　　金：装备预研领域基金重点项目(6140922010301);陕西省创新人才推进计划-科技创新团队项目(2017KCT-05);陕西省教育厅重点实验室科研计划项目(16JS044);国家自然科学基金项目(51705391);陕西省教育厅专项科学研究计划项目(17JK0383)资助

摘　　要：通过对Al-11.5Si-4Cu-2．6Ni-1Mg-0．45Fe的活塞合金熔体进行超声均匀化处理（处理温度720℃，超声功率分别为0，900，1500，2400，3000W），研究了施加到熔体的超声功率对合金凝固特性及显微组织的影响，提出了一种合金凝固冷却曲线特征值提取的数据处理方法，即运用Matlab软件对冷却曲线的一阶微分进行算术平均值过滤，二阶微分进行离散傅里叶变换过滤，采用微分热分析法快速提取冷却曲线特征值；对实验结果和冷却曲线分析发现，随着施加到熔体的超声功率的增加，初生Si析出温度、共晶反应温度升高，凝固进程加快；初生Si尺寸逐渐减小，形状越趋于圆整，体积分数降低，共晶硅长度逐渐缩短且发生钝化，α-Al相树枝晶二次枝晶间距增大，在超声功率1500W时有明显的等轴化趋势。但功率提高到3000W时，初生Si有明显的粗化趋势。超声能量的施加，影响了凝固过程，达到了细化初生两和共晶Si，改善α-Al相形貌的目的。The piston alloy （ Al-11.5Si-4Cu-1Mg-2.6Ni-0.45Fe） was ultrasonically processed at 720℃ with the ultrasonic power of 0, 900, 1500, 2400 and 3000 W, respectively. The effect of ultrasonic power on the solidification characteristics and mierostructure of alloy was analyzed. A new data processing method of characteristic value collecting from solidification cooling curves was put forwarded, which used Matlab on first order differential arithmetic mean filtering for the cooling curve, and second order differential discrete Fourier transform filtering, rapid extraction of cooling curve characteristic value with differential thermal analysis method. The resuhs showed that ： the temperature of primary silicon precipitation and the entectic reaction increased, and the solidification process was also accelerated with ultrasonic power increasing. The size and volume fraction of primary Si gradually decreased, and its shape became more and more rounded. The length of eutectic Si became shortened gradually and the passivation also occurred. The secondary dendrite spacing of α-Al phase dendrites increased with ultrasonic power increasing, equiaxed tendency appeared at 1500 W ultrasonic power. However, when the power was raised to 3000 W, the primary silicon showed obvious roughening tendency. By the application of ultrasonic energy, the solidification process was affected, which induced the primary Si and eutectic Si were refined, and the morphology of α-Al phase was also improved.

关 键 词：AL-SI合金 组合滤波法 凝固特性 活塞 显微组织 

分 类 号：TG146.2[一般工业技术—材料科学与工程]