Application of Imaging Techniques to Determine the Post-Yield Behaviour of the Heterogeneous Microstructure of Friction Stir Welds
Application of Imaging Techniques to Determine the Post-Yield Behaviour of the Heterogeneous Microstructure of Friction Stir Welds
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DOI：
10.1007/s11340-021-00722-9
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发表时间：
2021-04
影响因子：
2.4
通讯作者：
S. Ramachandran;A. Lakshminarayanan;Philippa Reed;J. Dulieu‐Barton
中科院分区：
文献类型：
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作者：
S. Ramachandran;A. Lakshminarayanan;Philippa Reed;J. Dulieu‐Barton
搅拌摩擦焊（FSW）会产生强烈的塑性变形和随后的热机械相互作用，导致局部非均匀的微观组织。为了了解焊缝的机械行为，有必要确定每个微观结构的子区域在weld. ESTA确定的局部微观结构和不同的微观结构区域的FSW.MethodsScanning电子显微镜（SEM）的机械行为之间的关系确定的微观结构的子区域的FSW接头。一种新的高分辨率数字图像相关（HR-DIC）的方法，使全场应变响应的确定，提供FSW子区域的机械行为。X射线计算机断层扫描（CT）确定的FSW和材料composition.ResultsThe晶粒形态在搅拌区的FSW变化与细晶粒结构的焊缝熔核和较大的晶粒中的热机械影响区（TMAZ）;晶粒较大的后退侧（RS）相比，前进侧（AS）。钨沉积物被发现在焊接熔核和归因于工具磨损。焊接子区域的机械性能表明，在搅拌区的材料具有更大的屈服强度比基体材料和搅拌摩擦焊的RS是更延性比焊缝熔核和AS侧。钨分布在搅拌区与当地的mechanical behavior.ConclusionsA新的方法相结合的显微组织观察与HR-DIC使，第一次，FSW子区域的机械行为，要与当地的晶粒形态和夹杂物所造成的工具磨损。
BackgroundFriction Stir Welding (FSW) causes intense plastic deformation and consequent thermomechanical interactions resulting in a localised heterogeneous microstructure. To understand the weld mechanical behaviour, it is necessary to identify each microstructural sub-region in the weld.ObjectiveDetermine the relationship between the local microstructure and mechanical behaviour of the different microstructural regions in a FSW.MethodsScanning electron microscopy (SEM) identified the microstructural sub-regions of an FSW joint. A novel High-Resolution Digital Image Correlation (HR-DIC) methodology enabled the determination of full-field strain response to provide the mechanical behaviour of the FSW sub-regions. X-ray computed tomography (CT) identified the geometry of the FSW and material composition.ResultsThe grain morphology in the FSW varied in the stir zone with a fine grain structure in the weld nugget and larger grains in the thermomechanical affected zone (TMAZ); the grains were larger in the retreating side (RS) compared to the advancing side (AS). Tungsten deposits were found in the weld nugget and attributed to tool wear. The mechanical properties of the weld subregions showed that the material in the stir zone had a greater yield strength than the base material and the RS of the FSW was much more ductile than the weld nugget and the AS side. The tungsten distributions in the stir zone correlated with the local mechanical behaviour.ConclusionsA novel methodology is developed that combines microstructural observations with HR-DIC enabling, for the first time, the FSW sub-region mechanical behaviour, to be related to the local grain morphology and inclusions caused by tool wear.