In the design of high-entropy alloys (HEAs) with desired properties, identifying the effects of elements plays an important role. HEAs with eutectic microstructure can be obtained by judiciously modifying the alloy compositions. In this study, the effect of Nb addition to FeCoNiCuNbx (x = 0.5, 5, 7.5, 11.6, 15) alloys was studied by varying the Nb concentration (at.%). FeCoNiCuNb0.5 HEA shows liquid phase separation to form Cu-rich and FeCoNiCu-rich phases. Detailed solidification paths are proposed for these alloys, which show eutectic, peritectic, and pseudo quasi-peritectic reactions. Increasing Nb content promotes the liquid phase separation tendency and causes the formation of Cu-rich spheres. The effect of Nb on the FeCoNiCu-rich phase was studied based on the nanoindentation and correlated with nanohardness. The compressive deformation properties of these alloys are studied at room temperature and high temperature and correlated with microstructure. Fractography results show the mode of fracture and are correlated with the microstructure obtained.

A series of hot compression tests of medium carbon Cr–Ni–Mo-alloyed steel, 34CrNiMo steel, were conducted on a Gleeble-1500 thermal mechanical simulator, in a wide temperature range of 1173–1423 K and at a strain rate range of 0.002–5 s−1. Three constitutive models, namely the Johnson–Cook (JC) model, strain compensated Arrhenius model, and the physically based constitutive model, were established to describe the hot deformation of 34CrNiMo steel. A comparative study of the three models was investigated by comparing the accuracy of prediction of flow stress behavior. The results imply that the JC model is not able to adequately represent the high-temperature flow behavior with the existance of recovery and recrystallization. The Arrhenius-type model based on mathematics has a good prediction in the flow stress behavior in all strain ranges during the hot deformation. The physically based constitutive model gives a better prediction accuracy of the deformation behavior in both flow stress and deformation mechanism.

The predictability of modified constitutive model, based on Arrhenius type equation, for illustrating the flow behavior of Fe–36%Ni Invar alloy was investigated via isothermal hot compression tests. The hot deformation tests were carried out in a temperature range of 850–1100 °C and strain rates from 0.01 to 10 s−1. True stress-true strain curves exhibited the dependence of the flow stress on deformation temperatures and strain rates, which then described in Arrhenius-type equation by Zener–Holloman parameter. Moreover, the related material constants and hot deformation activation energy (Q) in the constitutive model were calculated by considering the effect of strain as independent function on them and employing sixth polynomial fitting. Subsequently, the performance of the modified constitutive equation was verified by correlation coefficient and average absolute relative error which were estimated in accordance with experimental and predicted data. The results showed that the modified constitutive equation possess reliable and stable ability to predict the hot flow behavior of studied material under different deformation conditions. Meanwhile, Zener–Holloman parameter map was established according to the modified constitutive equation and used to estimate the extent of dynamic recrystallization.

Thermally stable nanosized Al2O3 particles and carbon nanotubes (CNTs) are comparatively effective in simultaneous improvement of strength and ductility of wrought magnesium alloy AZ31 when incorporated in microstructure. Understanding the comparative effectiveness of these nanosized reinforcements on the high temperature deformation process of wrought AZ31 alloy is important for its potential wider automotive body application. The current study has revealed that both reinforcements are competitively effective in inducing matrix grain and intermetallic particles refinement and strengthening almost to a theoretically predicted value. Although high temperature flow stress of AZ31 was found to closely match due to incorporation of both of the nanosized reinforcements, alumina was more efficient in improving the failure strain of matrix alloy. Addition of remarkably a small amount of nanosized alumina particles or CNTs introduced huge potential in near net shape formability of AZ31 alloy at a temperature much below than the widely used 350 °C. Among the two reinforcements used in this study, alumina was found to be more efficient when compared to the effect of CNTs.

A model has been developed to describe the rheology of austenite at high temperatures, characteristic from hot strip rolling of low-alloyed steels. It is based on the evolution of a single dislocation density through storage and strain rate-dependent dynamic recovery. The model gives good predictions of the stress-strain curves in a wide range of temperatures, strain rates and chemical compositions. It is now applied on industrial hot strip mills to predict the rolling loads of a wide range of industrial steels.