Recovery by triple junction motion in aluminium deformed to ultrahigh strains
Recovery by triple junction motion in aluminium deformed to ultrahigh strains
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DOI：
10.1098/rspa.2011.0097
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发表时间：
2011-11
期刊：
影响因子：
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通讯作者：
T. Yu;N. Hansen;Xiaoxu Huang
中科院分区：
文献类型：
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作者：
T. Yu;N. Hansen;Xiaoxu Huang
在宽的温度范围内（从室温到220°C）对真应变ε=2 ~ 5.5的工业纯铝进行退火，并使用透射电子显微镜（TEM）和电子背散射衍射（EBSD）技术表征微观结构的演变。基于结构形态将超细片层结构中的三重连接分为三类，并且制定三重连接的密度（每单位体积的长度）与边界间距之间的关系。在塑性变形过程中，三重结密度随应变的增加而增加，在等时退火和等温退火过程中，三重结密度随应变的增加而减小。基于TEM和EBSD观察，热激活的三重结运动被确定为在高应变铝恢复过程中的关键过程，导致在端部具有小二面角的薄薄片的去除和结构粗化。提出了一种由三重结运动恢复的机制，它可以支持一般的观察，即在退火过程中通过塑性变形形成的层状结构可以演变成等轴组织，在此之前进一步的结构粗化和再结晶。在此框架内，晶界上的三重结的表面张力进行了讨论的基础上表征变形和退火的显微组织的结构参数。
Commercial purity aluminium at true strains ϵ=2∼5.5 was annealed in a wide temperature range (from room temperature to 220°C), and the evolution of microstructure was characterized using transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) techniques. Triple junctions in an ultrafine lamellar structure are classified into three categories based on the structural morphology, and a relationship is formulated between the density (length per unit volume) of triple junctions and the boundary spacing. The triple junction density increases with increasing strain during plastic deformation and decreases during isochronal and isothermal annealing. Based on TEM and EBSD observations, thermally activated triple junction motion is identified as the key process during the recovery of highly strained aluminium, leading to the removal of thin lamellae with small dihedral angles at the ends and structural coarsening. A mechanism for recovery by triple junction motion is proposed, which can underpin the general observation that a lamellar structure formed by plastic deformation during annealing can evolve into an equiaxed structure, preceding further structural coarsening and recrystallization. Within this framework, the grain boundary surface tension on triple junctions is discussed based on the structural parameters characterizing the deformed and annealed microstructure.