The Deformation Response of Polycrystalline MAX Phases Under High Strain-Rate Loading.

MAX phases;High strain-rate;Materials Science and Engineering;Engineering;Materials Science and Engineering

Bhattacharya, RiddhimanWaas, Anthony M. ;

University of Michigan

关键词: MAX phases;    High strain-rate;    Materials Science and Engineering;    Engineering;    Materials Science and Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/133363/ribh_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Mn+1AXn phase ternary compounds (or MAX phases) are a relatively newer class of nano-layered, ternary compounds (carbides or nitrides) which exhibit unique combination of properties typical of ceramics and metals. Hence, they are attractive candidates for use in structural applications. However, the responses of MAX phases under dynamic loading conditions have not been characterized extensively. In this dissertation, experimental protocols to characterize representative MAX phases (Ti2AlC and Ti3SiC2) under high strain-rates are developed using a Split Hopkinson Pressure Bar (SHPB) set-up. It is observed that Ti2AlC shows significant inelastic deformation and relatively higher strains before fracture, even at very high strain-rates (~up to 4700 s-1), underlying cause of which is attributed to kink banding of the nano-layered structure at sub-grain length scale. On the other hand, Ti3SiC2 exhibits a response more typical of ceramics and therefore additional modification to the experimental set-up and protocols are necessary. Local strain field analysis using Digital Image Correlation (DIC) shows that strain evolution is heterogeneous, underlying origins of which can be related to existence of grain clusters. The clusters span several grains that are identified as discrete homogeneous patterns on the strain distribution maps. The geometric properties of a grain and neighboring grain effects by virtue of its position in polycrystalline MAX phase are of relevance in dictating the deformation modes. A computational model is developed to capture the effect of grain geometry and multi-axial stress state experienced by a grain in a polycrystalline material due to its neighbors and applied external loading.