Enhancement of chip breakability of aluminium alloys by controlling the solidification during direct chill casting
Enhancement of chip breakability of aluminium alloys by controlling the solidification during direct chill casting
复制标题
通过控制直接冷铸过程中的凝固提高铝合金切屑易碎性
DOI：
10.1016/j.jallcom.2020.158008
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发表时间：
2021-03-02
影响因子：
6.2
通讯作者：
Jarrett, Martin
中科院分区：
文献类型：
--
作者：
Barekar, Nilam S.;Skalicky, Ivan;Jarrett, Martin
对于直接冷硬 (DC) 铸造生产的铝坯而言，基体中自由加工元素的细化和均匀分散始终是理想的选择。传统的晶粒细化剂添加不能保证微观结构的均匀性和不溶相或金属间相的均匀分布。熔体调节直冷（MC-DC）铸造是产生均匀微观结构和细化第二相的关键技术。这种物理方法将传统的立式直冷 (DC) 铸造与直接浸入贮槽中的高剪切装置相结合，以进行原位微观结构控制。由于强制对流而增加的排热率、凝固前沿较大的温度梯度和较浅的贮槽有助于形成具有细枝晶臂间距的细等轴枝晶晶，有利于铸坯中第二相颗粒的细小和均匀分布。即使在热机械下游加工之后，这种微观结构特征的趋势也得以保留，从而大大提高了挤压实心棒材的机械加工性。 (C) 2020 Elsevier B.V. 保留所有权利。
Refinement and uniform dispersion of the free machining elements within the matrix is always desirable for aluminium billets produced by direct chill (DC) casting. The conventional grain refiner addition cannot ensure uniformity of microstructure and homogeneous distribution of insoluble or intermetallic phases. Melt conditioned direct-chill (MC-DC) casting is a key technology for producing uniform microstructure and refinement of secondary phases. This physical approach combines conventional vertical direct chill (DC) casting with a high shear device directly immersed in the sump for in situ microstructural control. Increased heat extraction rate due to forced convection, a larger temperature gradient at the solidification front and a shallower sump contribute to fine equiaxed dendritic grains with fine dendritic arm spacing that favor the fine and uniform distribution of second phase particles in the as-cast billet. This trend of the microstructural features was preserved even after thermomechanical downstream processing, giving rise to much improved machinability for the extruded solid bars. (C) 2020 Elsevier B.V. All rights reserved.