Advanced Materials Research Vols. 311-313

Abstract: The microstructure evolution and precipitation behavior of a low carbon high nitrogen martensitic stainless steel containing 15%Cr-5%Ni-1%Mo-0.16%N (in mass percentage) after tempering at temperatures ranged from 300 °C~700 °C were investigated by hardness test, X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The steel exhibits second hardening behavior after tempering at temperatures below 500 °C. Tempering at temperatures above 500 °C promotes the formation of reversed austenite and the precipitation of Cr₂N. The coherent orientation relationship of Cr₂N with martensite was revealed as , . Retained austenite originated from reversed austenite at room temperature results in the softening of the steel, and the retransformation of reversed austenite to untempered martensite after tempering at temperatures above 600 °C restores the hardness of the steel. σ phase was also found in specimens tempered at temperatures ranged from 500 °C to 700 °C.

Abstract: In order to predict forming limit curve for stainless steel sheet, the modified maximum force criterion (MMFC), introduced by Hora et al (1996 A prediction method for ductile sheet metal failure in FE-simulation Proc. Numisheet’96 Conf. pp 252–256), was adopted follow Swift’s hardening law. After comparing with experimental results, the improvement of MMFC model for FLD’s prediction were proposed based on Swift’s hardening law by representing work hardening coefficient as a function of strain ratio (β). The proposed MMFC model shows in good agreement between FLD’s computational and experimental result for stainless steel sheet. The results of proposed MMFC model also show that the stress-strain curves of sheets materials are difference at each strain ratio.

Abstract: This paper has reported a two-section model based on Temkin isotherm for interpreting the adsorption and inhibition properties of tinidazole on 45# carbon steel surface. The results show that the repulsion behavior between the adsorbed molecules turns into interattraction as the concentration of inhibitor is over 400mg/L. And additionally, the withdrawal of adsorbed molecules back into the bulk solution becomes thermodynamically favorable due to the formation of hemi-micelles.

Abstract: It is convenience to make plastic deformation by taking conventional cold rolling. By taking this technique on austenitic high manganese steel (Mn13) specimens, the hardness of Mn13 specimens increases. The mechanism of work hardening after conventional cold rolling is analyzed by studying the microstructure and electron diffraction pattern in depth. The research will make great significance to theory and practice.

Abstract: The effect of vanadium on the bainite transformation of medium carbon high silicon steel during air cooling was studied by using Optical Microscopy (OM) and Transmission Electron Microscopy (TEM). The mechanical properties of the test steels subjected to heat treatment were measured by tensile, hardness and impact tests. The results showed that, through the same heat treatment process, the microstructure of the V-alloyed steel was comprised of Carbide-Free Bainite (CFB, bainite + retained austenite) and martensite while the microstructure of the V-free steel was composed of ferrite/pearlite, which made the V-alloyed steels exhibit superior combination of strength, hardness and toughness to the V-free steel, but the elongation of the V-alloyed steel was worse than that of the V-free steel somewhat. Vanadium was helpful for the transformation of bainite in the tested medium carbon high silicon steel under air cooling condition. The carbon-enriched retained austenite films in the CFB enhanced the toughness of the V-alloyed steel.

Abstract: Polycrystalline α-HgI₂ films have been grown through combining vertical deposition method with hot wall vapor phase deposition (HWPVD) method. The influence of the α-HgI₂ seed layers on the structural and electrical properties of the polycrystalline α-HgI₂ films was investigated. It is found that the α-HgI₂ seed layers play an important role in reducing the grain sizes, increasing the density improving the crystallographic orientation and electrical properties of the polycrystalline α-HgI₂ films.

Abstract: Using the cold rolled High Strength IF Steel sheet of 1.0 mm thickness as the test material,the r value and recrystallization texture were investigated by the tensile test and X Radial Diffraction Device.The results show that the test steel were annealed by heating to 760°C,800°C,840°C and holding sixty seconds,and with the increase of the annealing temperature ,the recrystallization finished and the texture to obtain the full evolution,and the r value of the steel grown.After the annealing,the recrystallization texture shows strong γ-fiber texture,homogeneous γ-fiber and weak α-fiber texture,and the texture strength change rule with the annealing temperature change was gained.

Abstract: In this paper, three kinds of 12% Cr ferritic steels without Co and Cu, with 3%Co and with 3%Cu are produced. The addition Co and Cu lead to an evident increase in creep-resistant of the ferritic steel, and furthermore also markedly affect the fracture behavior. Microstructures were studied by comparing three kinds of the 12% ferritic steels to better understand different in those creep behaviors and fracture behaviors. It was found that the addition of Co and Cu not only inhibit the formation δ-ferrite but also are benefit for the growth of prior austenite grains. Additionally, the part of the added Cu precipitates in the matrix of the ferritic steel. These changes in microstructure and the solution of Co and Cu strengthen the ferritic steel.

Abstract: In order to explore the influence of the nitrogen concentrations on the impact toughness of the bearing steel GCr15，impact testing has been conducted on the steel samples with variant nitrogen contents (0.1-0.3 wt.%) on the tester JB－30B, and the fracture morphology of the samples after impact was investigated using scanning electron microscopy (SEM) and optical microscopy (OM). The results indicate that the impact toughness of the steel GCr15 with 0.1 wt.% nitrogen exhibits the lowest values with typical quasi-cleavage feature. The steel GCr15 with 0.2 wt.% nitrogen presents the maximum values in impact toughness associated with significant plastic deformation, suggesting ductile nature. The steel with 0.3 wt.% nitrogen presents a quasi-cleavage feature, and micro cracks observed beside the secondary precipitates. The impact toughness values of the steel with 0.3 wt.% nitrogen are higher than that with 0.1 wt.% nitrogen and lower than with 0.2 wt.% nitrogen. The results are valuable for a large-scale bench marked industrial manufacture of the bearing steel GCr15 with the optimized nitrogen concentrations.

Abstract: In order to study dynamic response of metal, this paper makes use of theoretical formula to investigate changes of temperature and grain size on steel target after the penetration of copper jet based on data gathered from the experiments. Deformed target penetrated by copper jet could be divided into superplastic deformation zone and normal deformation zone according to the different microstructure. Temperature distribution of each deformation zones is in turn calculated by two constitutive equations. The results indicate that areas with high temperature concentrate on the narrow zone near the penetrated channel. Then, the calculation of grain size conforms to the observation. It is obviously proven that the method used in this paper is trustworthy for calculating the changes of temperature and grain size of target caused by penetration.