金属熔体近壁面流动剪切模型及其对金属凝固影响的理论研究

发布时间：2019-06-06 06:09

【摘要】：本文建立了金属熔体近壁面流动剪切模型,并分析了流动剪切对金属凝固的影响.针对A356合金计算结果表明:层流流动的熔体内部剪应力随垂直斜板表面距离的增大而减小,随着流动长度的增加先急剧下降之后趋于稳定;紊流流动的熔体所受的剪应力随着垂直倾斜板表面距离的增大先急剧下降之后趋于稳定,随着流动长度的增加而不断增大;斜板倾角越大,斜板上相同位置的熔体层受到的剪应力越大;熔体垂直斜板表面距离越小,柱状晶所承受的弯曲应力越大;斜角越大,斜板上相同位置的柱状晶的弯曲应力越大;随着熔体在倾斜板表面流动长度的增加,在层流阶段,倾斜板表面柱状晶根部所受的弯曲应力先急剧下降之后趋于平稳,而在紊流阶段,弯曲应力是缓慢增加的;理论分析表明柱状晶在熔体近壁面流动过程受到的最大弯曲应力低于α-Al晶粒的屈服强度,所以斜板上熔体流动产生的弯曲力不能将柱状晶折断,只能将晶粒冲刷游离到熔体中使晶粒增殖,与实验结果相符合.所以本模型可以很好地解释熔体近壁面流动过程中的剪切本构关系以及剪应力对凝固组织的影响.
[Abstract]:In this paper, the flow shear model of metal melt near the wall is established, and the effect of flow shear on metal solidification is analyzed. The calculation results of A356 alloy show that the internal shear stress of laminar flow melt decreases with the increase of vertical inclined plate surface distance, and then tends to be stable with the increase of flow length. With the increase of the surface distance of the vertical inclined plate, the shear stress of the turbulent melt decreases sharply at first and then tends to be stable, and increases with the increase of the flow length. The larger the inclination angle of the inclined plate is, the greater the shear stress of the melt layer in the same position on the inclined plate is, and the smaller the surface distance of the vertical inclined plate is, the greater the bending stress of the columnar crystal is. The larger the oblique angle is, the greater the bending stress of columnar crystals in the same position on the inclined plate is. With the increase of melt flow length on the inclined plate surface, in the laminar flow stage, the bending stress on the columnar crystal root of the inclined plate surface decreases sharply at first and then tends to be stable, while in the turbulent stage, the bending stress increases slowly. The theoretical analysis shows that the maximum bending stress of columnar crystals near the wall is lower than the yield strength of 伪-Al grains, so the bending force produced by melt flow on inclined plates can not break columnar crystals. The grain can only be washed and dissociated into the melt to make the grain proliferate, which is in good agreement with the experimental results. Therefore, this model can explain the shear constitutive relation of melt near the wall and the effect of shear stress on solidification structure.
【作者单位】：东北大学材料与冶金学院;中国船舶重工集团公司第七二五研究所;兰州理工大学材料科学与工程学院;
【基金】：国家自然科学基金(批准号:51222405,51474063)资助的课题~~
【分类号】：TG111.4

【参考文献】