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ReportsA Crossover in the Mechanical Response of Nanocrystalline CeramicsMultimillion-atom molecular dynamics simulation of indentation of nanocrystalline silicon carbide reveals unusual deformation mechanisms in brittle nanophase materials, resulting from the coexistence of brittle grains and soft amorphous grain boundary phases. Simulations predict a crossover from intergranular continuous deformation to intragrain discrete deformation at a critical indentation depth. The crossover arises from the interplay between cooperative grain sliding, grain rotations, and intergranular dislocation formation similar to stick-slip behavior. The crossover is also manifested in switching from deformation dominated by indentation-induced crystallization to deformation dominated by disordering, leading to amorphization. This interplay between deformation mechanisms is critical for the design of ceramics with superior mechanical properties.
1 Department of Materials Science and Engineering, 1509 University Avenue, University of Wisconsin, Madison, WI 53706–1509, USA. * To whom correspondence should be addressed. E-mail: izabela{at}engr.wisc.edu
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Science. ISSN 0036-8075 (print), 1095-9203 (online)
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