Twin crystal structured Al-10 wt.% Mg alloy over broad velocity conditions achieved by high thermal gradient directional solidification
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2021年第12期
论文作者：Luyan Yang Shuangming Li Kai Fan Yang Li Yanhui Chen Wei Li Deli Kong Pengfei Cao Haibo Long Ang Li
摘 要：Twin crystal structured Al-10 wt.% Mg alloys that were grown over a broad solidification velocity range were prepared and studied for the first time. The high thermal gradient（G） and growth velocity（V） of directional solidification resulted in the dominant solidification of twins: the twinned dendrite trunks at constant high Vs curved in the G direction with large angles in 7 mm diameter crucibles and invaded regular columnar grains because of a distinct kinetics growth advantage. Transitive deceleration experiments were designed to produce twin crystals that evolved with lower values of V（100, 10, and 0.5μm/s） and had a structural coarsening trend. Twin cell growth in the absence of arms occurred at a growth velocity of 10 μm/s. A coherency loss was observed at a growth velocity of 0.5 μm/s with straight coherent twin boundaries turning into curved incoherent boundaries. Linear theoretical analyses were performed to understand the structural evolution of the twins. These results demonstrate the possibility of producing dense and controlled twin crystals in the Al-Mg system under most industrial production conditions; thus, this approach can be a new structural choice for designing Al-Mg-based alloys that have widespread commercial applications.
Luyan Yang1,2,3，Shuangming Li2，Kai Fan2，Yang Li2，Yanhui Chen1，Wei Li1，Deli Kong1,3，Pengfei Cao3，Haibo Long1，Ang Li1
1. Institute of Microstructure and Properties of Advanced Materials, Faculty of Materials and Manufacturing, Beijing University of Technology2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University3. Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich
摘 要：Twin crystal structured Al-10 wt.% Mg alloys that were grown over a broad solidification velocity range were prepared and studied for the first time. The high thermal gradient（G） and growth velocity（V） of directional solidification resulted in the dominant solidification of twins: the twinned dendrite trunks at constant high Vs curved in the G direction with large angles in 7 mm diameter crucibles and invaded regular columnar grains because of a distinct kinetics growth advantage. Transitive deceleration experiments were designed to produce twin crystals that evolved with lower values of V（100, 10, and 0.5μm/s） and had a structural coarsening trend. Twin cell growth in the absence of arms occurred at a growth velocity of 10 μm/s. A coherency loss was observed at a growth velocity of 0.5 μm/s with straight coherent twin boundaries turning into curved incoherent boundaries. Linear theoretical analyses were performed to understand the structural evolution of the twins. These results demonstrate the possibility of producing dense and controlled twin crystals in the Al-Mg system under most industrial production conditions; thus, this approach can be a new structural choice for designing Al-Mg-based alloys that have widespread commercial applications.
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