Meso-scale microstructural agglomerate quantification in boron carbide using X-ray microcomputed tomography

• Published in: Materials characterization Vol. 141; pp. 177 - 185
• Main Authors: Moorehead, Carli A., Sietins, Jennifer M., Swab, Jeffrey J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2018
• Subjects: Boron carbide; BORON CARBIDES; CERAMICS; COMPRESSION; COMPRESSION STRENGTH; COMPUTERIZED TOMOGRAPHY; Defect analysis; DISTRIBUTION; HOT PRESSING; MATERIALS SCIENCE; MICROSTRUCTURE; SURFACES; X RADIATION; X-ray computed tomography; X-ray computed tomography; Defect analysis; Boron carbide
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2018.04.053

Failure in brittle materials is governed, in part, by the specific microstructure of that material, with heterogeneous microstructures generally leading to reduced mechanical properties and performance. In ceramics used for armor, an increase in compressive strength can be an indicator of improved ballistic performance. In hot-pressed boron carbide (B4C) ceramic plates, failure has been attributed to carbonaceous flakes observed on the fracture surfaces of failed specimens. However, this current work shows agglomerates, in addition to the carbonaceous flakes, are present in this boron carbide. The density and distribution of these agglomerates are believed to influence the ballistic performance. Therefore, it is of interest to improve the quantification of meso-scale microstructural agglomerates so that strategies can be developed to mitigate them. This work is focused on the microstructural characterization of dumbbell-shaped compression specimens that were machined from a single tile of pressure-aided densification (PAD) B4C, using high-resolution micro-computed tomography (microCT). Large clusters of non-B4C agglomerates, up to 125 μm in diameter, were observed in addition to the typical smaller carbonaceous flakes and aluminum-based phases. Agglomerate size distribution, orientation, morphology, and spacing were quantified both parallel and perpendicular to the pressing direction. This defect quantification provides valuable information for a better understanding of the material microstructure which is a critical step in improving armor materials for the future. •First known quantification of agglomerate defect distributions comprising of carbonaceous and aluminum nitride phases B4C.•In-depth statistical analyses of the size, orientation, and morphology of the defects.•The determination of directional dependence of the hot-pressing direction on the agglomerate distributions.