Rotary friction welding is one of the most crucial techniques for joining different parts in advanced industries. Experimentally measuring the history of thermomechanical and microstructural parameters of this process can be a significant challenge and incurs high costs. To address these challenges, the finite element method was used to simulate thermomechanical and microstructural aspects of the welding of identical superalloy Inconel 718 tubes. Numerical simulation results were used to compute essential mechanical and metallurgical parameters such as temperature, strain, strain rate, volume fraction of dynamic recrystallization, and grain size distribution. These parameters were subsequently verified using experimental test results. The Johnson–Avrami model was utilized in the microstructural simulation to convert thermomechanical parameters into metallurgical factors, employing a FORTRAN subroutine. The calculated thickness of the recrystallization zone in the wall was 480 and 850 μm at the tube wall’s center and edge, respectively. These values were reported from experimental measurements as 500 and 800 μm, respectively. The predicted grain size changes from the center to the edge of the wall thickness, near the weld interface, ranged from 2.07 to 2.15 μm, comparable to the experimental measurements ranging from 1.9 to 2.2 μm. Various curves are also presented to explore the correlation between thermomechanical and microstructural parameters, with the experimental results revealing predictable microstructure evolutions correlated with thermomechanical changes.

The thermo-mechanical behavior of nanosized Al₂O₃ particles reinforcing aluminum was analyzed in the present paper. The material was prepared by spark plasma sintering and friction stir welding. The thermal stresses affecting the composite behavior during welding were modeled through COMSOL MultiPhysics, and the results were validated by the analyses of the composites’ mechanical properties. The spark-plasma-sintered materials presented limited porosity, which was taken into account during the modeling phase. Both model and experiments revealed that higher heat input is related to better material mixing during welding and sound mechanical properties. Thermal stresses lead to residual stresses close to 300 MPa in the thermo-mechanically affected zone for processing conditions of 1900 RPM and 37 mm/min. This leads to an increase in hardness up to 72 HV.

In this work, we propose a hybrid approach to solve the challenge of balancing strength and ductility in aluminum (Al) matrix composites. While some elements of our approach have been used in previous studies, such as in situ synthesis and ex situ augmentation, our work is innovative as it combines these techniques with specialized equipment to achieve success. We synthesized nanoscale Al₃BC particles in situ using ultra-fine particles by incorporating carbon nanotubes (CNTs) into elemental powder mixtures, followed by mechanical activation and annealing, to obtain granular (UFG) Al. The resulting in situ nanoscale Al₃BC particles are uniformly dispersed within the UFG Al particles, resulting in improved strength and strain hardening. By innovating the unique combination of nanoscale Al₃BC particles synthesized in situ in UFG Al, we enabled better integration with the matrix and a strong interface. This combination provides a balance of strength and flexibility, which represents a major breakthrough in the study of composites. (Al₃BC, CNT)/UFG Al composites exhibit simultaneous increases in strength (394 MPa) and total elongation (19.7%), indicating increased strength and suggesting that there are promising strengthening effects of in situ/ex situ reinforcement that benefit from the uniform dispersion and the strong interface with the matrix. Potential applications include lightweight and high-strength components for use in aerospace and automotive industries, as well as structural materials for use in advanced mechanical systems that require both high strength and toughness.

Joining of stainless steel to carbon steel is widely used in various industries. Resistance spot welding (RSW) is a suitable process for joining steel sheets. Due to the complexity and importance of optimizing the parameters, numerical simulation of this process was considered. In this research, the electrical-thermal-mechanical simulation of RSW of 304 stainless steel to St37 carbon steel was performed using finite element method (FEM). Then, the simulated weld nugget size was compared with the experimental results of optical microscopy (OM). In addition, diffusion of metallic elements of the steels in the molten region was simulated using Fick’s equation and compared with experimental results of energy-dispersive X-ray spectroscopy (EDS). It was shown that diffusion of Cr and Ni through the weld nugget, would make a new stainless steel structure. Microstructure prediction of the heat affected zone (HAZ) was performed using Koistinen–Marburger and Leblond–Devaux equations to predict the percentage of martensite and ferrite-perlite phases during the heating and cooling stages of the specimens from room temperature to the peak temperature and cooling down under the M_f temperature. The results of this simulation were validated by scanning electron microscopy (SEM) images and shear tensile and micro-hardness test results. The simulation results showed that increasing the heat input from 1250 A during 0.5 s to 3750 A during 1.5 s, increases the percentage of martensite, from 40% to 80%, in the HAZ and widens the martensite region.