In this paper, TiAl-Nb sheets were fabricated via elemental foil metallurgy using Ti, Al, and Nb foils. The microstructure of the TiAl-Nb sheet was regulated by a two-step heat treatment process, which involved short-time holding at 1410 °C, 1430 °C and 1450 °C, followed by long-time holding at 1150 °C. Subsequently, the microstructure of the sheet was analyzed, emphasizing the orientation relationship and interface structure between the B2/β phase, Ti₃Al phase, and the TiAl matrix. The results indicated that, subsequent to diverse heat treatment processes, the TiAl-Nb sheet comprised α₂(Ti₃Al) and B2/β phases at the grain boundaries and within the grains, whereas the matrix structure was γ(TiAl). After TiAl-Nb sheets were heat-treated at 1410 °C for 3 min and then at 1150 °C for 2 h, the microstructure of the sheets was observed to be composed of relatively fine lamellar structures. The TiAl phase, Ti₃Al phase and B2/β phase existed in the form of coherent interfaces with extremely small misfit degrees. The interfacial energy between phases was small, making it easier to obtain an alloy microstructure with a higher content of the γ(TiAl) phase. To further provide a basis for the selection of heat treatment processes, the matrix method analysis indicated that, after holding at 1410 °C for 3 min and subsequently at 1150 °C for 2 h, the TiAl phase and Ti₃Al phase in the sheet structure exhibited obvious preferred orientations. A short β-phase holding (3 min) followed by a long α + γ two-phase holding was an effective process route for obtaining a fine lamellar structure.

Owing to the low stiffness of thin-walled workpieces, disturbances can readily arise during milling, severely compromising machining accuracy and surface quality. This study proposes a new viscoelastic model of a magnetorheological elastomer (MRE) and analyzes its vibration reduction performance under dynamic cutting forces. First, the governing equations of the system are derived from Newton’s second law, and the amplitude-frequency response curves are obtained using the harmonic balance method. The analytical results are then validated by Runge–Kutta numerical integration, with good agreement between the two approaches. Next, the vibration reduction performance of the MRE-based viscoelastic nonlinear energy sink (MNES) and the effects of its parameters are analyzed. Finally, the nonlinear stiffness coefficient and damping ratio are varied simultaneously at different mass ratios to identify the optimal parameter ranges for the MRE-based viscoelastic nonlinear energy sink of magnetorheological elastomer. The results show that the maximum amplitude of the main system first decreases and then increases as the nonlinear stiffness increases. With appropriate parameter selection, the MRE-based viscoelastic nonlinear energy sink of magnetorheological elastomer provides better vibration reduction performance than the traditional nonlinear energy sink. In addition, as the mass ratio increases, the minimum attainable value of the main-system amplitude initially decreases and then approaches a constant, while the optimal ranges of the nonlinear stiffness coefficient and damping ratio widen slightly. By combining a set of calculated parameters with the differential constitutive equation of the magnetorheological elastomer, the corresponding stress–strain curve is obtained. This provides guidance for the fabrication of magnetorheological elastomers with favorable vibration-damping performance. The stability of milling chatter is also analyzed. The calculated stability lobe diagram and supplementary time-domain verification results show that a milling system with the MNES can effectively suppress chatter and allow a greater depth of cut.

This study investigates the hot-deformation behavior and dynamic recrystallization (DRX) kinetics of 12Cr2Mo1V steel for heavy forgings of large hydrogenation reactors. Gleeble isothermal compression tests were performed at 950–1200 °C and strain rates of 0.01–5 s⁻¹ with friction correction to obtain reliable flow–stress data. A strain-compensated Arrhenius constitutive model was established to characterize the hot flow behavior over the entire strain range, with R = 0.9918 and AARE = 3.8826%. The dynamic material model was used to determine the optimal stable processing window of 1000–1200 °C and 0.01–0.1 s⁻¹. Microstructural analyses reveal that continuous dynamic recrystallization (CDRX) dominates grain evolution below 1100 °C, while discontinuous dynamic recrystallization (DDRX) prevails at higher temperatures. A mechanism-segmented DRX model with a 1100 °C transition threshold is proposed to precisely describe the temperature-dependent dual-DRX kinetics of the studied steel. The calibrated constitutive equation and segmented DRX sub-models were embedded into the DEFORM finite-element software for coupled thermo-mechanical–microstructural simulations, and the simulated microstructures agree well with experimental results. This work supports refined numerical simulation and process-parameter optimization of heavy reactor forgings, while providing a convenient and efficient modeling strategy for alloys with temperature-dependent dual-DRX mechanisms.