Polyurethane (PU) has been used in a variety of industries during the past few years due to its exceptional qualities, including strong mechanical strength, good abrasion resistance, toughness, low-temperature flexibility, etc. More specifically, PU is easily “tailored” to satisfy particular requirements. There is a lot of potential for its use in broader applications due to this structure–property link. Ordinary polyurethane items cannot satisfy people’s increased demands for comfort, quality, and novelty as living standards rise. The development of functional polyurethane has recently received tremendous commercial and academic attention as a result. In this study, the rheological behavior of a polyurethane elastomer of the PUR (rigid polyurethane) type was examined. The study’s specific goal was to examine stress relaxation for various bands of specified strains. We also suggested the use of a modified Kelvin–Voigt model to describe the stress relaxation process from the perspective of the author. For the purpose of verification, materials with two different Shore hardness ratings—80 and 90 ShA, respectively—were chosen. The outcomes made it possible to positively validate the suggested description in a variety of deformations ranging from 50% to 100%.

The paper is devoted to studying the chemical elements distribution in the material’s structure depending on the manufacturing technological parameters and their effect on properties of a new self-lubricating antifriction composite based on powder nickel alloy EP975 with CaF₂ solid lubricant for operation at temperature 800 °C and loads up to 5.0 MPa, in air. The study is focused on the features of alloying elements distribution in the composite matrix, which depends on the manufacturing technology. A uniform distribution of all alloying elements in the studied composite was shown. The chemical elements’ uniform distribution in the material is associated with one of the most important preparatory technological operations in the general manufacturing technology used. This is a technological operation of mixing powders with subsequent analysis of the finished mixture. The uniform distribution of chemical elements determines the uniform arrangement of carbides and intermetallics in the composite. General manufacturing technology, which includes the main operations, such as hot isostatic pressing technology and hardening heat treatment, contributed to the obtainment of a practically isotropic composite with almost the same properties in the longitudinal and transverse directions. Because of the composite’s structural homogeneity, without texturing, characteristics are isotropic. Improving the material’s structural homogeneity helps to keep its mechanical and anti-friction qualities stable at high temperatures and stresses in the air. The performed studies demonstrated the correctness of the developed manufacturing technology that was confirmed by the electron microscopy method, micro-X-ray spectral analysis, mechanical and tribological tests. The developed high-temperature antifriction composite can be recommended for severe operating conditions, such as friction units of turbines, gas pumping stations, and high-temperature units of foundry metallurgical equipment.

The potentials of CuZnAlNi shape memory alloys to serve as viable reinforcement in Aluminium matrix composites (AMCs) was investigated. The AMCs were double stir cast developed, containing 4, 6, and 8 wt% CuZnAlNi particles; and their structural characteristics and mechanical properties were compared with that of the unreinforced Al alloy and AMC containing 8 wt% SiC. Scanning electron microscopy and X-ray diffraction results show that the CuZnAlNi refined the grain size, and increase in the CuZnAlNi wt% resulted in the formation of varied AlCu-based intermetallics, apart from the primary Al rich phase. The strength indicators – hardness, ultimate tensile strength, and specific strength largely improved with increase in the CuZnAlNi wt% and were comparatively higher than that of the unreinforced Al alloy and AMC reinforced with 8 wt% SiC for the 6 and 8 wt% CuZnAlNi reinforced AMC (specific strength being the only exception). The percentage elongation and fracture toughness values of the AMCs reinforced with CuZnAlNi (12–14.5% and 10.5–12.3 MPa m ^1/2 ) were equally superior to the SiC reinforced AMC (9% and 6.5 MPa m ^1/2 , respectively). However, a partial reduction in the % elongation was observed with the increase in the CuZnAlNi wt%. Improved matrix/particle interface bonding, matrix refinements, thermoelastic-induced compressive residual stresses, inherent ductile, and tough nature of the SMA were advanced as mechanisms responsible for the improvements in properties.