Exotic grain growth law in twinned boron carbide under electric fields

Abstract

Grain growth is a ubiquitous phenomenon in all materials, and it affects both structural and functional prop- erties. Despite its intrinsic importance, a full comprehension of grain growth from a fundamental point of view—i.e., from the nanoscale to the macroscale—is still a pending issue. In practical terms, our knowledge relies on the classical kinetic laws reported sixty years ago. This paper reports the violation of such classical laws in boron carbide ceramics consolidated by spark plasma sintering. The conjunction of high temperature gradients with large compressive stress when a pulse electric current passes through the ceramic powders gives rise to an intense twinning–detwinning formation. These forming steps at the grain boundaries change the grain mobility drastically. Therefore, a new ‘exotic’ law for grain-growth kinetics is found and validated at different temperatures and dwell times.