Critical temperature-dependent shear band formation in CoCrNi alloy under high-temperature dynamic compression.

In numerous engineering applications, the occurrence of highly rapid loading conditions, coupled with significant temperature rise, is prevalent. Under these harsh conditions, shear localization is a prominent material failure mechanism, which may result in catastrophic failure. Generally, materials possessing higher strength, limited work hardening rate, and lower thermal conductivity are more prone to mechanical instability. However, in the current study, a cryo-rolled CoCrNi alloy, characterized by much higher strength and limited work hardening, shows remarkable room and high-temperature mechanical performance under impact loading except at one temperature domain∼600 °C where this material displays mechanical instability by exhibiting adiabetic shearband. To shed light and understand this abnormal mechanical response, an in-depth microstructural study revealed that the ASB formation is closely linked to the recrystallization behavior of this alloy that is invariantly related to the stored energy of cold work, test temperature, and strain rate. Uniquely, the amplified nano-twinning activity at high strain rate and critical temperature promoted the fragmentation of grains and facilitated recrystallization, respectively. Once the recrystallization is completed, the alloy regains work hardening ability even at very high test temperatures, reaching 900 °C due to the deformation of the newly recrystallized matrix. The present work is valuable in delineating the alloy's application domain for rigorous impact and crash-worthiness applications, as there exists a dearth of literature on this material for dynamic scenarios. • Cryo-rolling introduces extensive twinning in CoCrNi. • Dynamic hot compression from room temperature to 900 °C. • Formation of shear band at only one critical temperature ∼600 °C,neither below nor above this temperature. • Dynamic strain rate induced secondary and tertiary twins fragment the deformed matrix into nano-sized blocks. • Shear band formation and propagation linked to stored energy of cold work and ambient test conditions. [ABSTRACT FROM AUTHOR]