Morphological evolution of the solid-liquid interface near grain boundaries has been studied during directional solidification of succinonitrile-based transparent alloys (SCN-0.9wt%DCB). Experimental results show that...Morphological evolution of the solid-liquid interface near grain boundaries has been studied during directional solidification of succinonitrile-based transparent alloys (SCN-0.9wt%DCB). Experimental results show that the grain boundary provides the starting point of morphological instability of the solid-liquid interface. The initial perturbation near the grain boundary is significantly larger than other perturbations on the interface. The initial shape of the interface and the competition between the thermal direction and preferred crystalline orientations determine the subsequent growth pattern selections. The temporal variations of the curvature radius of cell/ridge tips near the grain boundary have also been studied when the instability occurs. This process is divided into three parts. As the pulling velocity increases, dendrites at the grain boundary grow in two different directions to form a bicrystal microstructure. Side branches on either side of the dendrite exhibit different growth patterns.展开更多
文摘选择三种不同醋酸乙烯酯(VAc)含量的EVA,采用熔融共混和接枝共聚方法制备增初改性PVC合金,考察EV A结构和合金制备方法对合金力学性能的影响。随着EVA添加量的增加,熔融共混制备的VAc含量为15%(质量分数,下同)的EVA/PVC合金的抗冲强度先缓慢增加、接着快速上升、再缓慢增大的变化趋势,而V A c含量为20%和25%的EVA改性的PVC合金的抗冲强度则先增加后降低;EVA的加入使合金的拉伸强度降低,加入高VAc含量的EVA,下降更明显。相同EV A添加量时,采用接枝共聚制备的PVC/EVA合金的抗冲强度远大于熔融共混制备的PVC/EVA合金,断面呈现典型的韧性断裂形貌。
基金supported by the National Natural Science Foundation of China (Grant Nos.61078057 and 51172183)NPU Foundation for Fundamental Research (Grant Nos.NPU-FFR-JC201048 and JC201155)+1 种基金the Science & Technology Program of Shanghai Maritime University (Grant No.20110054)the Project of the Excellent Youth of Shanghai (WANG CaiFang)
文摘Morphological evolution of the solid-liquid interface near grain boundaries has been studied during directional solidification of succinonitrile-based transparent alloys (SCN-0.9wt%DCB). Experimental results show that the grain boundary provides the starting point of morphological instability of the solid-liquid interface. The initial perturbation near the grain boundary is significantly larger than other perturbations on the interface. The initial shape of the interface and the competition between the thermal direction and preferred crystalline orientations determine the subsequent growth pattern selections. The temporal variations of the curvature radius of cell/ridge tips near the grain boundary have also been studied when the instability occurs. This process is divided into three parts. As the pulling velocity increases, dendrites at the grain boundary grow in two different directions to form a bicrystal microstructure. Side branches on either side of the dendrite exhibit different growth patterns.
