Effects of Adiabatic Heating and Strain Rate on the Dynamic Response of a CoCrFeMnNi High-Entropy Alloy

Abstract

This work presents a comprehensive analysis of the effects of strain and strain rate on the adiabatic heating and the mechanical behavior of a CoCrFeMnNi high-entropy alloy (HEA). In this investigation, compression tests were carried out at quasi-static and dynamic strain rates. The temperature of the specimens was measured using high speed infrared thermography. The high strain rate tests were conducted with a Split Hopkinson Pressure Bar, and the tests at lower strain rates were performed using a universal testing machine. The material exhibited a positive strain rate sensitivity, as true stress-strain plots were shifted upwards with the increase in strain rate. With exception of the isothermal tests, temperature rise and the Taylor-Quinney coefficient (β) were noticeably similar for the investigated strain rates. This study shows that the common assumption that β can be considered 0.9 and constant is possibly not very accurate for the CoCrFeMnNi alloy. The β is influenced by at least strain and strain rate.

Effect of grain size on strength and strain rate sensitivity in the CrMnFeCoNi high-entropy alloy

“…Experimental data from the literature [13,16,17,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] was used to validate the model and these data are summarized in Table 2 where it is evident that results were collected for a wide range of grain sizes, strain rates and temperatures. The present model considers the spatial grain size but the majority of these data evaluate the grain size using 2D-sections so that there will be some level of inaccuracy for this parameter.…”

Influence of Strain History on Dynamic Strain Localization and Stress State During High-Rate Tensile Loading of Titanium Alloys: Experiments, Modeling, and Analytical Methods

“…This results in an increase of temperature within the sample, proportional to the plastic work per unit of volume dissipated in the material (the area under the true stress-strain curve), commonly referred as adiabatic heating. On the contrary, the heating at low strain rates is very small [42]. During dynamic experiments on pristine samples the total amount of plastic work is dissipated in adiabatic conditions, while on pre-strained samples part of the plastic work is dissipated at quasi-static rates of strain.…”

Influence of Strain Rate on Plastic Deformation of the Flange in Steel Road Barrier

“…This behaviour can be analysed by the use of the Taylor–Quinney coefficient (β INT ) [ 12 , 13 ]. This coefficient can be derived from the first law of thermodynamics taking into consideration the adiabatic conditions as follows [ 14 , 15 ]: where W p is incremental plastic work, ρ refers to the density, C p heat capacity of the deformed matrix, and Δ T is the temperature growth. β INT expresses how much plastic energy is converted to heating and which fraction is directly stored in the matrix in the form of lattice imperfections [ 14 , 15 ].…”

“…This coefficient can be derived from the first law of thermodynamics taking into consideration the adiabatic conditions as follows [ 14 , 15 ]: where W p is incremental plastic work, ρ refers to the density, C p heat capacity of the deformed matrix, and Δ T is the temperature growth. β INT expresses how much plastic energy is converted to heating and which fraction is directly stored in the matrix in the form of lattice imperfections [ 14 , 15 ]. It is well known that the Taylor–Quinney coefficient β INT is usually less than 1 in the cases when other heat sources are not involved [ 16 ].…”

“…Smith [ 18 ] reported thermal softening during plastic deformation at high strain rates employing the Taylor–Quinney coefficient. Soares et al [ 14 ] as well as Rittel [ 15 ] investigated the influence of strain rate on β INT in the high entropy alloys and the glassy polymers.…”