超声空化对大规格高强铝合金热顶铸造凝固组织的影响及作用机理  

Effect rules and function mechanism of ultrasonic cavitation on solidification microstructure of large size high-strength aluminum alloy with hot top casting

作　　者：李瑞卿[1] 李晓谦[1] 陈平虎[1] 郭兴[1] 张敏[1] LI Ruiqing LI Xiaoqian CHEN Pinghu GUO Xing ZHANG Min(State Key Laboratory of High Performance Complex Manufacturing, School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China)

机构地区：[1]中南大学机电工程学院,高性能复杂制造国家重点实验室,湖南长沙410083

出　　处：《中南大学学报（自然科学版）》2016年第10期3354-3360,共7页Journal of Central South University:Science and Technology

基　　金：国家重点基础研究发展计划(973计划)项目(2012CB619504);国家自然科学基金资助项目(51475480,51575539)~~

摘　　要：在直径为650 mm的高强铝合金热顶半连续铸造中施加多源超声波振动系统,考察多源超声场的施加对铸锭宏微观组织的影响,并分析热顶铸造过程中超声空化作用对熔体凝固的作用机理。研究结果表明:铸锭截面组织整体均匀细化,晶粒形状由发达的枝晶变为等轴枝晶,晶粒平均粒度减小了107μm,在超声辐射杆附近区域,细化效果最明显;在热顶铸造过程中,铝液中的超声空化范围主要在辐射杆附近有限区域内,故空化效应主要作用于液态金属中的异质颗粒,空化泡崩溃产生的冲击波增大了异质颗粒与液态金属的接触角,降低了形核所需自由能,促使异质形核发生,增大了形核率,细化了凝固组织。Multi-source ultrasonic vibration system was imposed on high-strength aluminum alloy melt which was in diameter 650 mm hot top semi-continuous casting to explore the effect and mechanism of multi-source ultrasonic field on ingot macrostructure and microstructure. The results show that the ingot organization overall refines, grain shape changes from developed dendrite into equiaxed dendrite, the average grain size decreases by 107 μm, refining effect is most obvious on region around the ultrasonic radiation. In hot top casting process, the region of cavitation mainly lies in a limited area near radiation rod in aluminum liquid. Cavitation activates the heterogeneous particles in the liquid metal, the shock wave generated by collapse of cavitation bubbles increases the contact angle of heterogeneous particles and liquid metal, reduces the nucleation free energy, promotes heterogeneous nucleation occurs, increases the nucleation rate and refines solidification structure.

关 键 词：超声空化 高强铝合金 热顶铸造 

分 类 号：TG148[一般工业技术—材料科学与工程] TB559[金属学及工艺—金属材料]