A Multiscale Characterization And Analysis Of Deformation Heterogeneity In Additively Manufactured 316L Stainless Steel

Laser additive manufacturing is a new manufacturing process,which can produce complex parts directly.It has been considered one of the twelve disruptive technologies that determine the future economy and the cornerstone to developing intelligent manufacturing.For its layer-by-layer process,laser additive manufactured materials are significantly heterogeneous in microstructure and anisotropy in mechanical property.A good understanding of the interaction mechanism between inherent microstructures and deformation heterogeneities is important,which can help us understand deformation behavior,optimize the manufacturing process and thus improve the whole property.Based on micro-DIC and EBSD,unique microstructures and deformation heterogeneities have been characterized.Furthermore,we try to struggle with the inner association between the inherent microstructures and local deformations of AM materials,which can help to give a better understanding of “manufacturing processmaterial microstructure-mechanical properties”.The main conclusions are as follows,taking additive manufacturing of 316 L stainless steel as the research object:This work has characterized the structural characteristics of additively manufactured 316 L stainless steel at multiple scales.On the mesoscale,the characteristics include the melt pool boundary,such as the deposited layer interface and track interface.On the microscale,the characteristics include the grain morphologies and intragranular substructures.Mechanical properties of additivemanufactured 316 L stainless steel materials also have been studied,and the influence of the deposition interface on the anisotropy of the mechanical properties of the materials has been confirmed.This work has tried a new way to adopting additive manufacturing microstructure texture as the speckle feature of digital image correlation,and the quality of this kind of natural speckle has been evaluated.A combination of microscopic digital image correlation and electron backscatter diffraction technology,multi-scale characterization of microstructure characteristics,and plastic deformation localization is characterized.The influence of mesoscale structure characteristics in materials on strain localization is studied.Quantitatively characterizes the phenomenon that the local concentration zone of strain penetrates the deposition interface.It is found that the difficulty of penetrating the interface between the tracks and the interface between the layers is different.Compared with the layer interface,the track interface has more grain boundaries and high local dislocations,which hinder the transmission of strain.The influence of grains and sub-grains on the local strain distribution on the microscopic scale was studied.Studies have shown that on the grain scale,strain localization tends to be related to the morphology of the grains,and the average strain has large differences between grains;in the sub-grain range,the unique substructure in grains of additive manufacturing materials plays an important role in the localization of plastic strain and damage nucleation.