Magnetorheological elastomers (MREs) are magneto-sensitive smart materials, widely used in various applications, i.e., construction, automotive, electrics, electronics, medical, minimally invasive surgery, and robotics. Such a wide field of applications is due to their superior properties, including morphological, dynamic mechanical, magnetorheological, thermal, friction and wear, and complex torsional properties. The objective of this review is to provide a comprehensive review of the recent progress in isotropic MREs, with the main focus on their properties. We first present the background and introduction of the isotropic MREs. Then, the preparation of filler particles, fabrication methods of isotropic MREs, and key parameters of the fabrication process—including types of polymer matrices and filler particles, filler particles size and volume fraction, additives, curing time/temperature, and magnetic field strength—are discussed in a separate section. Additionally, the properties of various isotropic MREs, under specific magnetic field strength and tensile, compressive, or shear loading conditions, are reviewed in detail. The current review concludes with a summary of the properties of isotropic MREs, highlights unexplored research areas in isotropic MREs, and provides an outlook of the future opportunities of this innovative field.

Cyclic quenching and tempering (QT) heat–treatment processes have the potential to improve the mechanical properties of steel due to the formation of fine grain size microstructure. This work aims to investigate the mechanical and corrosion properties of experimental medium carbon low alloy steel under cyclic heat–treatment processes. Cyclic single quenching and tempering (SQT), double quenching and tempering (DQT), and triple quenching and tempering (TQT) heat–treatment processes were carried out on the medium carbon low alloy steel. X–ray diffraction analysis validated the formation of fine ε–carbide (Fe_2.4C) after intermediate low–temperature tempering in DQT and TQT heat–treatments. These fine carbides provided preferential nucleation sites for the formation of new austenitic grain, resulting in a refined microstructure composed of supersaturated (carbon) lath martensite (α′) and retained austenite (γ). The DQT and TQT heat–treatments improved 19% tensile strength, 100% elongation, and 95% impact absorption energy in comparison to SQT heat–treatment. DQT and TQT heat–treatments also transformed the brittle behavior of SQT steel into a ductile behavior. It was also revealed by the small number and size of dimples along with a large number of short tear ridges in fractographs. Morphology of corrosion products of heat–treated experimental steel was also studied in a 5% NaCl solution. The SQT heat–treated sample showed porous morphology of corrosion products, while the TQT sample showed morphology with less porosity on the surface. The DQT sample showed solid corrosion morphology with little porosity. As the grain size went on decreasing in the cyclic heat–treatments the corrosion rate was also dropped.

The quenched–partitioned–tempered (QPT) steel is one of the novel steel in third–generation advanced high strength steels. Herein, an attempt has been made to investigate the microstructure, mechanical, and electrochemical properties of QPT steel as a function of tempering time. Microstructural analysis reveals that a high volume fraction of martensite with low fractions of retained austenite and bainite were achieved after 30 sec of tempering. Mechanical tests validated that this triplex composite microstructure resulted in an 18% improvement in Vickers hardness, 73% in tensile strength (Rm) with little reduction of 12% elongation (ƐT) in comparison to non–heat treated steel sample. Tempering for 90 sec increased the volume fractions of stable retained austenite, bainite and decreased the fractions of martensite by carbon diffusion to austenite. Further increase in tempering time stabilized retained austenite at an expense of bainite and martensite phases, resulting in reduced hardness and improved strength and elongation. Electrochemical analysis of the QPT heat–treated samples performed in 3.5% NaCl solution showed that the high corrosion rate was yielded from the steel sample tempered for 30 sec, while other samples tempered for 90 to 150 sec showed much lower corrosion rate than non–heat–treated steel sample.