Comparative analysis of microstructural and mechanical properties in BCC and FCC metals subjected to localized blast loads

Blast loading generates intense shock waves that produce inhomogeneous strain, leading to severe plastic deformation or failure through mechanisms such as twinning, dislocation multiplication, and grain morphology evolution. Understanding the influence of crystal structure on mechanical and microstructural response under such conditions is critical for designing materials for protective and structural applications. This study investigates the behavior of body-centered cubic (BCC) Ferritic Stainless Steel (FSS 430) under localized blast loads and compares it with face-centered cubic (FCC) Austenitic Stainless Steel (ASS 316L), building on our previous work under similar loading conditions. Square test plates, 2mm thick, with circular areas of 106 mm in diameter, were exposed to localized blast loads. Post-blast evaluation was examined using micro-tensile testing to assess changes in mechanical properties, while electron backscatter diffraction (EBSD) was used to interrogate strain localization, twinning activity, and dislocation storage. The results revealed distinct crystal-structure-dependent responses. BCC-structured FSS 430 showed highly localized strain accumulation, characterized by the formation of very low-angle grain boundaries (VLAGBs) and activation of blast-induced twinning on the {332}<113> system. In contrast, FCC-structured ASS 316L exhibited a relatively homogeneous strain distribution, dominated by annealing twins on {111}<112> and close-packed slip on {111}<110>, with non-octahedral slip on {100}<110> as a secondary mechanism. The findings also highlighted while both structures exhibited similar deflection and strain distribution, the superior ability of FCC alloys to distribute strain uniformly and better energy absorption, while BCC alloys tended to concentrate deformation in isolated regions, increasing susceptibility to localized failure.