Probing the degenerate pattern growth of {100}<011> orientation in a directionally solidified Al-4.5 wt% Cu alloy  

作　　者：Yumin Wang Shuangming Li Zhenpeng Liu Hong Zhong Lei Xu Hui Xing 

机构地区：[1]State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an,710072,China [2]College of Materials Science and Engineering,Qingdao University of Science and Technology,Qingdao,266000,China [3]MOE Key Laboratory of Material Physics and Chemistry under Extraordinary,Shaanxi Key Laboratory of Condensed Matter Structure and Properties,Northwestern Polytechnical University,Xi'an,710129,China

出　　处：《Journal of Materials Science & Technology》2019年第7期1309-1314,共6页材料科学技术（英文版）

基　　金：financially supported by the National Natural Science Foundation of China (No. 51474174);Research Funds of the State Key Laboratory of Solidification Processing in NWPU (No. SKLSP201714)

摘　　要：Degenerate pattern is a seemingly disordered morphology but it exhibits the inherently ordered crystal connected with tip-splitting and limited stability which makes it difficult to observe in the metallic system. Here we employ(100)[011] orientated planar-front seeds using directional solidification and reveal the fundamental origins of the degenerate pattern growth in an Al-4.5 wt% Cu alloy. We find that the spacing of the tip-splitting(λ) in the degenerate of the alloys followed a power law,λ∝V^-0.5, and the frequency(f) of the splitting was related to the growth velocity(V) by f ∝V^1.5. The dimensionless growth direction(θ/θ0) increased monotonously and approached 0.6 with faster velocity, attributed to its anisotropy in the interface kinetics. Once growth velocity exceeded a threshold, two types of pattern transitions from degenerate to regular dendrites were proposed. One of them exhibited a random and chaotic mode and the other underwent a rotation in growth direction.Degenerate pattern is a seemingly disordered morphology but it exhibits the inherently ordered crystal connected with tip-splitting and limited stability which makes it difficult to observe in the metallic system. Here we employ（100）[011] orientated planar-front seeds using directional solidification and reveal the fundamental origins of the degenerate pattern growth in an Al-4.5 wt% Cu alloy. We find that the spacing of the tip-splitting（λ） in the degenerate of the alloys followed a power law,λ∝V-0.5, and the frequency（f） of the splitting was related to the growth velocity（V） by f ∝V1.5. The dimensionless growth direction（θ/θ0） increased monotonously and approached 0.6 with faster velocity, attributed to its anisotropy in the interface kinetics. Once growth velocity exceeded a threshold, two types of pattern transitions from degenerate to regular dendrites were proposed. One of them exhibited a random and chaotic mode and the other underwent a rotation in growth direction.

关 键 词：AL-CU alloy Anisotropy Direction SOLIDIFICATION DEGENERATE pattern 

分 类 号：TG[金属学及工艺]