脉冲磁场作用下矩形截面宽厚比对K4169高温合金晶粒细化的影响  

EFFECT OF RECTANGLE ASPECT RATIO ON GRAIN REFINEMENT OF SUPERALLOY K4169 UNDER PULSED MAGNETIC FIELD

作　　者：滕跃飞 李应举[1] 冯小辉[1] 杨院生[1] 

机构地区：[1]中国科学院金属研究所,沈阳110016

出　　处：《金属学报》2015年第7期844-852,共9页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目51034012;国家重点基础研究发展计划项目2010CB631205资助~~

摘　　要：研究了脉冲磁场作用下K4169高温合金矩形截面试件的凝固组织以及具有不同宽厚比矩形截面试件的晶粒细化效果,计算模拟了脉冲磁场作用下试件熔体中电磁场和流场的分布情况,并对细化机理进行了分析.实验结果表明,施加脉冲磁场后,K4169高温合金矩形试件的凝固组织得到了不同程度的细化,当试件宽厚比为1时,施加脉冲磁场可以使凝固组织晶粒显著细化;随着试件宽厚比增大,脉冲磁场的晶粒细化效果减弱.计算模拟结果表明,脉冲磁场在熔体中产生周期性的压-拉电磁力,导致熔体产生周期性振荡和呈环流形式的对流.在相同磁感应强度的脉冲磁场作用下,试件宽厚比越接近1,试件内的电磁力和流速越大,有利于模壁晶核游离及枝晶臂破碎,从而使晶粒得到细化.The researches on the grain refinement by applied pulsed magnetic field（PMF） during solidification have received much attention in recent years and lots of positive experimental results indicate that it is a potential method for controlling solidification process. Various grain refinement mechanisms under PMF are proposed and most of them are considered to be relevant to the convection of melt driven by the electromagnetic force. An obvious fact is that the forced convection caused by PMF is strongly limited by the shape of the melt. However,most of previous studies were focused on the cylindrical samples rather than rectangular ones, and actually the later one was widely used in industry. The aim of this work is to investigate the influence of PMF on the grain refinement of K4169 superalloy rectangular samples with various aspect ratios. Grain refinement of K4169 superalloy under PMF was experimentally investigated in the rectangular samples with the aspect ratios of 1.0, 2.0, 4.5 and 5.5on the transverse section. In order to study the influence of aspect ratio on the forced convection, the distributions of the electromagnetic field, electromagnetic force and melt flow caused by PMF were numerically simulated by finite element software ANSYS. The experimental results show that the grains of the K4169 rectangular samples are coarse equaxied grains without PMF and the grain size slightly decreases with the increase of aspect ratio. Underthe PMF with same excitation voltage and frequency, the grains are refined remarkably in the sample with the aspect ratio of 1.0. As the aspect ratio is increased, the grain refinement effect can still be observed but not such obvious. The numerical simulation results indicate that the periodic pushing-pulling electromagnetic force is induced by the PMF, which drives the melt to vibrate and flow circularly. Under the same PMF, the electromagnetic force and fluid rate decreases with the increase of aspect ratio. When the aspect ratio increases from 1.0 to 5.5, the average electr

关 键 词：高温合金 晶粒细化 脉冲磁场 宽厚比 数值模拟 

分 类 号：TG290[金属学及工艺—铸造]