Crack propagation in AA3xxx during deep drawing investigated using a combined TKD/dictionary indexing approach

The influence of dispersoids and grain boundary characteristics on the crack propagation behavior in AA3xxx during deep drawing has been investigated using scanning transmission electron microscopy, energy-dispersive spectroscopy, and the dictionary indexing method applied to transmission Kikuchi diffraction (TKD) patterns. Observations showed that cracks formed on the surface of the material at the earliest stages of deformation and lengthened with increasing deformation. Subsurface analysis showed that the cracks propagated from the surface and bifurcated as they extended deeper into the material, forming branches. All of the observed cracks followed intergranular paths with bifurcations correlating with triple junction locations, but no strong trends were found relating grain boundary characteristics to the crack propagation pathway. Dispersoids located at the grain boundaries were found where cracks terminated, suggesting that dispersoids arrest crack propagation and divert crack growth pathways. This paper demonstrates the first practical application of combining the dictionary indexing method with TKD analysis. Graphic abstract

Automated summary

The influence of dispersoids and grain boundary characteristics on the crack propagation behavior in AA3xxx during deep drawing was investigated, with cracks typically forming on the material surface at the earliest stages of deformation and extending with increasing strain. The cracks propagated along intergranular paths with bifurcations correlating with triple junction locations, but no strong trends were identified linking grain boundary characteristics to crack propagation pathways. Dispersoids at grain boundaries were found to arrest crack propagation and divert crack growth pathways, demonstrating the first practical application of combining the dictionary indexing method with TKD analysis.