For further knowledge about the refining performance of AlTiC master alloys, Al5.5Ti0.25C and Al6.5Ti0.5C master alloys containing high Ti and C content were prepared and used in grain refining experiments of 99.8% co...For further knowledge about the refining performance of AlTiC master alloys, Al5.5Ti0.25C and Al6.5Ti0.5C master alloys containing high Ti and C content were prepared and used in grain refining experiments of 99.8% commercial pure aluminum(CPAl). Their performance was compared with two types of Al5Ti1B refiners whose performance was nowadays considered to be the best. These two types of master alloys show similar refining efficiency at the addition level of 0.2%. However, at the addition level of 0.5%, there still exists great performance difference between AlTiC and Al5TiB alloys in grain refinement of 99.98% and 99.995% high purity aluminum(HPAl). The growth of columnar grains is fully suppressed due to the refinement of AlTiC at the addition level of 0.5%. Also, at the same addition level, the grain refining experiments of Al3Ti0.15C and Al5Ti0.2C master alloys which have found initial commercial applications are conducted in the above-mentioned three types of pure aluminum. According to the experimental results, these two refiners of different compositions are both nonideal. The second phase particles extracted from each refiner were observed through TEM, while the nuclei of grains after grain refinement were observed through SEM. The results were analyzed through computation and comparison of the constitutional-supercooling parameter and the growth-restriction parameter whose values were determined by solute element in aluminum melt with different purity. Apparently, AlTiC master alloys with high content of Ti and C element have great refining potential.展开更多
利用Fletcher模型对过饱和水汽在燃煤细颗粒表面异质核化特性进行了数值预测，对不同粒径段燃煤细颗粒的形态进行扫描电镜（scanning electron microscopy，SEM）分析，并用分形理论对细颗粒物的结构特征进行描述，考察其对细颗粒异质...利用Fletcher模型对过饱和水汽在燃煤细颗粒表面异质核化特性进行了数值预测，对不同粒径段燃煤细颗粒的形态进行扫描电镜（scanning electron microscopy，SEM）分析，并用分形理论对细颗粒物的结构特征进行描述，考察其对细颗粒异质核化性能的影响。结果表明，实验用的燃煤细颗粒表面具有典型的分形结构，分形维数在2．21-2．63；燃煤细颗粒的不规则结构能使液滴胚胎形成临界吉布斯自由能降低、成核速率增大、核化所需的临界过饱和度降低，可提高过饱和水汽在其表面的成核能力；此外，核化所需临界过饱和度随颗粒粒径增大而降低，特别是小于0．1μm的颗粒，粒径对过饱和度的影响更为显著，随温度提高核化所需的临界过饱和度相应降低。展开更多
基金Project (51074033) supported by the National Natural Science Foundation of China
文摘For further knowledge about the refining performance of AlTiC master alloys, Al5.5Ti0.25C and Al6.5Ti0.5C master alloys containing high Ti and C content were prepared and used in grain refining experiments of 99.8% commercial pure aluminum(CPAl). Their performance was compared with two types of Al5Ti1B refiners whose performance was nowadays considered to be the best. These two types of master alloys show similar refining efficiency at the addition level of 0.2%. However, at the addition level of 0.5%, there still exists great performance difference between AlTiC and Al5TiB alloys in grain refinement of 99.98% and 99.995% high purity aluminum(HPAl). The growth of columnar grains is fully suppressed due to the refinement of AlTiC at the addition level of 0.5%. Also, at the same addition level, the grain refining experiments of Al3Ti0.15C and Al5Ti0.2C master alloys which have found initial commercial applications are conducted in the above-mentioned three types of pure aluminum. According to the experimental results, these two refiners of different compositions are both nonideal. The second phase particles extracted from each refiner were observed through TEM, while the nuclei of grains after grain refinement were observed through SEM. The results were analyzed through computation and comparison of the constitutional-supercooling parameter and the growth-restriction parameter whose values were determined by solute element in aluminum melt with different purity. Apparently, AlTiC master alloys with high content of Ti and C element have great refining potential.
文摘利用Fletcher模型对过饱和水汽在燃煤细颗粒表面异质核化特性进行了数值预测，对不同粒径段燃煤细颗粒的形态进行扫描电镜（scanning electron microscopy，SEM）分析，并用分形理论对细颗粒物的结构特征进行描述，考察其对细颗粒异质核化性能的影响。结果表明，实验用的燃煤细颗粒表面具有典型的分形结构，分形维数在2．21-2．63；燃煤细颗粒的不规则结构能使液滴胚胎形成临界吉布斯自由能降低、成核速率增大、核化所需的临界过饱和度降低，可提高过饱和水汽在其表面的成核能力；此外，核化所需临界过饱和度随颗粒粒径增大而降低，特别是小于0．1μm的颗粒，粒径对过饱和度的影响更为显著，随温度提高核化所需的临界过饱和度相应降低。
