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利用稀土La对液态A356铝合金进行了细化处理,并在电磁搅拌技术下制备了半固态A356-La铝合金浆料,研究了稀土La和电磁搅拌对半固态A356铝合金初生相形貌的影响,并用分形维数对其初生相形貌进行了表征.结果表明,添加适量的稀土La可有效改善半固态A356铝合金初生相的形貌,无论是否经过电磁搅拌,随着稀土添加量的增加,A356铝合金的初生相形貌均呈先变好后恶化的演变规律,当稀土La的添加量为0.4%(质量分数)时,其初生a相的形貌和尺寸均达到最佳,其平均等积圆直径为88.85μm,平均形状因子为0.78;当稀土La的添加量相同时,经过电磁搅拌作用的A356-La铝合金初生a相的平均等积圆直径均比未经过电磁搅拌的更小,其形状因子则相反,均比未经过电磁搅拌的更大,说明经过电磁搅拌的半固态A356铝合金初生a相比未搅拌过的更细小、圆整,即经过电磁搅拌的初生a相形貌更佳,如当La含量为0.4%时,其平均等积圆直径由88.85μm降至84.14μm,平均形状因子由0.78升至0.81.此外,实际的合金凝固组织具有分形特征,应用分形几何的原理来描述和分析半固态铝合金中初生相的形貌变化规律甚至初生相形成机理是完全可能的.且不同工艺参数下所获得的半固态铝合金初生相形貌具有不同的分形维数,随着半固态初生相由树枝状向颗粒状或球状变化,其分形维数逐渐变小.
The rare-earth La was used to refine the liquid A356 aluminum alloy and the semi-solid A356-La aluminum alloy slurry was prepared by electromagnetic stirring technology. The effects of rare earth La and electromagnetic stirring on the morphology of primary phase of semi-solid A356 aluminum alloy The results show that the addition of the proper amount of rare earth La can effectively improve the morphology of the primary phase of the semi-solid A356 aluminum alloy, with or without electromagnetic stirring, with the addition of rare earth The morphology of the primary phase of A356 aluminum alloy shows the evolution of the morphology of the primary phase of the A356 aluminum alloy. When the addition amount of the rare earth La is 0.4% (mass fraction), the morphology and size of the primary phase a, The average equivalent circle diameter is 88.85μm and the average shape factor is 0.78. When the addition amount of rare earth La is the same, the average equivalent circle diameter of the primary a phase of A356-La aluminum alloy subjected to electromagnetic stirring is higher than that without electromagnetic stirring Of the smaller, the shape factor is the opposite, than without electromagnetic stirring greater, indicating that after the electromagnetic stirring of semi-solid A356 aluminum alloy a is not stirred than the original finer, round, that is, after electromagnetic stirring nascent A phase morphology is better, such as When the content of La is 0.4%, the average equivalent circle diameter decreases from 88.85μm to 84.14μm, and the average shape factor increases from 0.78 to 0.81. In addition, the actual alloy solidification structure has the fractal characteristics, and the principle of fractal geometry is used to describe and It is possible to analyze the morphologies of the primary phases and even the formation of primary phases in the semi-solid aluminum alloy.The morphologies of the primary phases of the semi-solid aluminum alloy obtained under different technological parameters have different fractal dimensions, The primary phase changes from dendritic to granular or globular, and its fractal dimension becomes smaller gradually.