Origin of the separated alpha-Al nanocrystallization with Si added to Al86Ni9La5 amorphous alloy
Origin of the separated alpha-Al nanocrystallization with Si added to Al86Ni9La5 amorphous alloy
复制标题
Al86Ni9La5非晶合金中添加Si分离α-Al纳米晶的起源
DOI：
10.1016/j.matchar.2021.111199
复制
发表时间：
2021
影响因子：
4.7
通讯作者：
Li J. F.
中科院分区：
文献类型：
--
作者：
Yi J. J.;Kong L. T.;Ferry M.;Tang C. G.;Sha G.;Li J. F.
了解纳米晶化是控制纳米晶增强非晶合金组织和性能的重要前提。本文系统地研究了Al86Ni9La5和(Al86Ni9La5)98Si2非晶合金及其退火产物的微观结构，揭示了初生α-Al的纳米晶化行为随Si加入量的变化而发生显著变化的原因。加热时，α-Al在两种非晶态合金的富铝区域形核。Si的加入显著缩小了非晶态样品中单一富铝区的尺寸，但提高了局部最大Al浓度，减缓了溶质原子的扩散速度。结果表明，在较低的温度下，α-Al的初晶化首先在富Al区以较高的形核率进行。然而，富含溶质元素的残余非晶相直到合金加热到足以发生大规模原子扩散的温度时才会晶化，α-Al的进一步晶化是通过现有α-Al晶体的外延生长进行的。Si与Ni，特别是La之间的高结合强度是导致α-Al纳米晶化分成两个阶段的原因。
An understanding of nanocrystallization is an important precondition for controlling the microstructure and properties of nanocrystal-reinforced amorphous alloys. In the present work, the microstructures of Al86Ni9La5and (Al86Ni9La5)98Si2amorphous alloys and their annealed products were investigated systematically to reveal why the nanocrystallization behavior of primary α-Al was considerably changed with Si addition. Upon heating, α-Al nucleates in the Al-rich regions of two amorphous alloys. The addition of Si significantly shrinks the size of single Al-rich region in the as-quenched amorphous sample, but raises the local maximum Al concentration and slows down the rate of diffusion of solute atoms. As a result, the primary crystallization of α-Al first takes place at a higher nucleation rate in the Al-rich regions at lower temperatures. However, the residual amorphous phase enriched with solute elements does not crystallize until the alloy is heated to a high enough temperature for massive atomic diffusion to occur, with further crystallization of α-Al occurring through epitaxial growth of the existing α-Al crystals. The high bonding strength between Si with Ni, and especially La, is responsible for the splitting of α-Al nanocrystallization into two stages.