Abstract The effect of Al–5Ti–1B master alloy addition level on the grain size of 7055 aluminum alloy was studied by the standard T-golf method and the free growth model. The features of the commercial Al–5Ti–1B master alloy were analyzed by X-ray diffraction (XRD), optical microscope (OM) and scanning electron microscope (SEM). The size distribution of TiB2 particles in the Al–5Ti–1B master alloy is well fitted by a log-normal function. The cooling curve of 7055 aluminum alloy is measured by a thermocouple. As the amount of Al–5Ti–1B master alloy increases, the grain size of the 7055 aluminum alloy decreases rapidly first and then becomes slowly. When the refiner content exceeds 0.5 wt%, the grain size tends to be stable, and the refinement limit is about 40 μm. The grain sizes were calculated by the free growth model with input of cooling rate, solute concentration, addition level of Al–5Ti–1B master alloy and size distribution of TiB2 particles. The prediction results are basically consistent with the experimental results. The fractions of active TiB2 particles are less than 5% at all addition levels and the efficiency progressively decreases with addition level. The grain size distribution is progressively uniform with the increase of Al–5Ti–1B master alloy addition. As the grain size of the 7055 aluminum alloy decreases, the second phases are diffusely distributed on the grain boundaries. So the area fraction of coarse second phases is reduced, and the defects such as porosities are also reduced.

中文翻译：

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Al-5Ti-1B中间合金孕育7055铝合金晶粒尺寸预测与研究

摘要 采用标准T-golf法和自由生长模型研究了Al-5Ti-1B中间合金添加量对7055铝合金晶粒尺寸的影响。通过 X 射线衍射 (XRD)、光学显微镜 (OM) 和扫描电子显微镜 (SEM) 分析了商业 Al-5Ti-1B 中间合金的特征。Al-5Ti-1B 中间合金中 TiB2 颗粒的尺寸分布很好地符合对数正态函数。7055铝合金的冷却曲线是用热电偶测量的。随着Al-5Ti-1B中间合金用量的增加，7055铝合金的晶粒尺寸先快速减小，然后变慢。当细化剂含量超过0.5wt%时，晶粒尺寸趋于稳定，细化极限约为40μm。晶粒尺寸由自由生长模型计算，输入冷却速度，溶质浓度、Al-5Ti-1B 中间合金的添加量和 TiB2 颗粒的尺寸分布。预测结果与实验结果基本一致。在所有添加水平下，活性 TiB2 颗粒的比例都小于 5%，并且效率随着添加水平的增加而逐渐降低。随着Al-5Ti-1B中间合金添加量的增加，晶粒尺寸分布逐渐均匀。随着7055铝合金晶粒尺寸的减小，第二相扩散分布在晶界上。因此粗大的第二相的面积分数减少了，气孔等缺陷也减少了。在所有添加水平下，活性 TiB2 颗粒的比例都小于 5%，并且效率随着添加水平的增加而逐渐降低。随着Al-5Ti-1B中间合金添加量的增加，晶粒尺寸分布逐渐均匀。随着7055铝合金晶粒尺寸的减小，第二相扩散分布在晶界上。因此粗大的第二相的面积分数减少了，气孔等缺陷也减少了。在所有添加水平下，活性 TiB2 颗粒的比例都小于 5%，并且效率随着添加水平的增加而逐渐降低。随着Al-5Ti-1B中间合金添加量的增加，晶粒尺寸分布逐渐均匀。随着7055铝合金晶粒尺寸的减小，第二相扩散分布在晶界上。所以粗大的第二相的面积分数减少了，气孔等缺陷也减少了。