The residual stress generated in a superalloy during heat treatment affects the subsequent processing of the workpiece and may even adversely affect its performance. This paper investigates the effects of pre-stretching (in the range from 0% to 9%) before aging treatment on residual stress generated during quenching process and microstructure of Inconel 718 superalloy. After pre-stretching treatment, the residual stress deriving from quenching process can be well reduced. When the pre-stretch level was 3%, the quenching residual stress reached a maximum reduction of 72%, and the strength increased by 7.1%, while the product of strength and elongation hardly changed. Simultaneously, the microstructures of the pre-stretched specimens are observed by electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). It was found that the fraction of high-angle grain boundaries in the alloy decreased while that of low-angle grain boundaries increased with increasing pre-stretch level. As the pre-stretch level was further increased to 9%, the proliferating entanglement of internal dislocations in the specimen was intensified, resulting in rod-shaped γ″ precipitates coarsening and volume fraction reduction of precipitates, which further led to a reduction in the product of strength and elongation of material.

In this study, isothermal compression tests of TB18 titanium alloy were conducted using a Gleeble 3800 thermomechanical simulator for temperatures ranging from 650 to 880 °C and strain rates ranging from 0.001 to 10 s⁻¹, with a constant height reduction of 60%, to investigate the dynamic softening mechanisms and hot workability of TB18 alloy. The results showed that the flow stress significantly decreased with an increasing deformation temperature and decreasing strain rate, which was affected by the competition between work hardening and dynamic softening. The hyperbolic sine Arrhenius-type constitutive equation was established, and the deformation activation energy was calculated to be 303.91 kJ·mol⁻¹ in the (α + β) phase zone and 212.813 kJ·mol⁻¹ in the β phase zone. The processing map constructed at a true strain of 0.9 exhibited stability and instability regions under the tested deformation conditions. The microstructure characteristics demonstrated that in the stability region, the dominant restoration and flow-softening mechanisms were the dynamic recovery of β phase and dynamic globularization of α grains below transus temperature, as well as the dynamic recovery and continuous dynamic recrystallization of β grains above transus temperature. In the instability region, the dynamic softening mechanism was flow localization in the form of a shear band and a deformation band caused by adiabatic heating.

This study systematically investigates the influence of quenching (850–910 °C) and tempering (160–280 °C) temperatures on the microstructural evolution and mechanical properties of a novel low-alloy ultra-high-strength martensitic steel (UHSMS). Comprehensive microstructural characterization combined with mechanical testing demonstrates that quenching at 880 °C results in the finest martensitic laths and the highest dislocation density, leading to an excellent strength–toughness balance. Subsequent tempering treatments reveal that the specimen tempered at 200 °C achieves an optimal combination of properties, with a yield strength of 1517 MPa, ultimate tensile strength of 2017 MPa, elongation of 10.4%, and impact toughness of 80.3 J/cm². This optimum is mechanistically linked to a cooperative effect where the fine tempered martensitic structure and stable film-like retained austenite (RA) enhance toughness and ductility, while the nano-scale precipitates (forming during the ε→θ carbide transition) simultaneously provide substantial precipitation strengthening, thereby minimizing the strength sacrifice typically associated with improved toughness. Furthermore, the 200 °C tempered specimen exhibits the largest shear lip on the tensile fracture surface and the maximum dimple size on the impact fracture surface, indicative of a high plastic strain capacity and excellent crack propagation resistance.