The hot deformation behavior and workability of a new reduced activation ferritic/martensitic steel named SIMP steel for accelerator-driven system were studied. The flow curve and its microstructure were studied at 900-1200°C and strain rate range of 0.001-10 s-1. The results showed that the deformation behavior of the SIMP steel during hot compression could be manifested by the Zener-Hollomon parameter in an exponent-type equation. Based on the obtained constitutive equation, the calculated flow stresses were in agreement with the experimentally measured ones, and the average activity energies Q DRV and Q HW for the initiation of dynamic recrystallization and the peak strain were calculated to be 476.1 kJ/mol and 462.7 kJ/mol, respectively. Furthermore, based on the processing maps and microstructure evolution, the optimum processing condition for the SIMP steel was determined to be 1050-1200°C/0.001-0.1 s-1 .
This work studied the effect of alloying Mn by selective laser melting on the microstructure and biodegradation properties of pure Mg. The grains in the microstructure were quasi-polygon in shape. The average grain size was similar (~10 μm) for the SLMed Mg-xMn with different Mn contents. The XPS spectra of the corrosion surface showed that alloying Mn into Mg by SLM produced a relatively protective manganese oxide film, which contributed to decreasing the biodegradation rate. All the results of the electrochemistry test, immersion test and the corrosion surface morphologies coincided well. The SLMed Mg-0.8Mn had the lowest biodegradation rate. When Mn content was more than 0.8 wt.%, the influence of the undissolved Mn phase on the decrease of the biodegradation resistance counteracted the influence of the relatively protective manganese oxide layer on the increase of the biodegradation resistance.
This research investigates the mechanical properties of a Cr-Ni-Mo-alloyed rock drill steel tempered at different temperatures from 150 to 550 C. The highest strength, hardness, and impact energy occur when the steel is tempered at 180 C. Strength, hardness, and impact energy decrease with increasing tempering temperature from 180 to 400 C. For tempering temperatures higher than 400 C, the steel exhibits: 1) an increase in impact energy; 2) an increase in strength and hardness when tempered at 420, 450, and 480 C; and 3) a gradual decrease in strength and hardness when tempered at temperature higher than 480 C. The mechanism of the changes of impact energy and hardness with tempering temperature is proposed.
This work investigated the tensile characteristics of plain C–Mn steel with an ultrafine grained ferrite/cementite (UGF/C) microstructure and coarse-grained ferrite/pearlite (CGF/P) microstructure. The tensile tests were performed at temperatures between 77 K and 323 K. The lower yield and the ultimate tensile strengths were significantly increased when the microstructure was changed from the CGF/P to the UGF/C microstructures, but the total elongation and the uniform elongation decreased. A microstructural change from the CGF/P microstructure to the UGF/C microstructure had an influence on the athermal component of the lower yield and the ultimate tensile strengths but not on the thermal component. The UGF/C microstructure with a higher carbon content provided a higher strength without losing ductility because cementite particles restrained necking.
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