The H13-mod steel optimized by composition and heat treatment has reached the performance index of the shield machine hob. The hot deformation behavior of the H13-mod steel was investigated by compression tests in the temperature range from 900 to 1150 °C and the strain rate range from 0.01 to 10 s⁻¹. The true stress-strain curve showed that the rising stress at the beginning of deformation was mainly caused by work hardening. After the peak stress was attained, the curve drop and the flow softening phenomenon became more obvious at low strain rates. The flow behavior of the H13-mod steel was predicted by a strain-compensated Arrhenius-type constitutive equation. The relationship between the material constant in the Arrhenius-type constitutive equation and the true strain was established by a sixth-order polynomial. The correlation coefficient between the experimental value and the predicted value reached 0.987, which indicated that the constitutive equation can accurately estimate the flow stress during the deformation process. A good linear correlation was achieved between the peak stress (strain), critical stress (strain) and the Zener‒Hollomon parameters. The processing maps of the H13-mod steel under different strains were established. The instability region was mainly concentrated in the high-strain-rate region; however, the microstructure did not show any evidence of instability at high temperatures and high strain rates. Combined with the microstructure and electron backscattered diffraction (EBSD) test results under different deformations, the optimum hot working parameters were concluded to be 998–1026 °C and 0.01–0.02 s⁻¹ and 1140–1150 °C and 0.01–0.057 s⁻¹.

In this paper, the relationships between the thermomechanical treatments (TMT), the microstructural evolution the mechanical properties of Ti17 alloy were investigated. The results indicate the coarsening behavior of lamellar α was sensitive to the aging temperature during the process of TMT. The thickness of lamellar α changed from 0.19 to 0.38 μm with an increase in the aging temperature. Moreover, both tensile properties and impact toughness vary with the thickness of lamellar α. The tensile strength increases with the increase of the thickness of lamellar α the plasticity and impact toughness the opposite trend. The quantitative investigations found that there is a linear relationship between the tensile properties and the thickness of lamellar α the tensile properties could be adjusted in the range of 1191~1062 MPa and 1163~1039 MPa to obtain ultimate tensile strength and yield strength as well as 11~16% elongation and 23~33% reduction of area by varying the thickness of lamellar α. Meanwhile, the impact toughness could be adjusted in the range of 46 ~53 J/cm². The high correlation coefficients imply that the linear equation is reliable to describe the relationships between the mechanical properties and the thickness of lamellar α for Ti17 alloy.

In the present study, quenching and partitioning (Q & P) treatment of a medium-carbon silicon-rich steel was processed by a dilatometer. The volume fraction of the retained austenite at different partitioning times was determined by X-ray diffraction (XRD). The metastable austenite transformation process after different partitioning times was studied by a combination of dilatometry, XRD, and transmission electron microscopy (TEM). Analysis of the transformation kinetics of metastable austenite during partitioning by means of dilatometry and the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation was carried out. The results show that the volume fraction of retained austenite increases first and then decreases with the increase of the partitioning time. The transformation active energy Q = 141 kJ·mol⁻¹ and the Avrami exponent n = 1. The transformation product of metastable austenite is needle-like bainite, which grows perpendicularly towards the boundary of the austenite. Finally, the blocky austenite was divided into lath-shaped forms.