Advanced Materials Research Vols. 581-582

Abstract: Influence of strain rate on mechanical properties of Fe-30Mn-3Si-4Al TWIP steel was studied by compression experiments, indicating that TWIP steel has strain rate softening effect, strain rate insensitivity, and also strain rate hardening effect. According to strain rate sensitivity m changing with strain rate, effect of strain rate on TWIP steel mechanical properties can be divided into three stages: quasi-static stage with strain rate ranging from 0.001 to 100 1/s; high-strain rate stage with strain rate ranging from 701 to 5108 1/s; super-high-strain rate stage with strain rate ranging from 10335 to 30147 1/s. Adiabatic temperature rise tends to increase with strain rate. Strain hardening exponent is divided into three parts: dislocation strengthening stage, twinning strengthening stage and thermal softening stage.

Abstract: Two types of super martensitic stainless steels (Cr13 and Cr15) were designed. The effect of tempering process on their microstructure, mechanical properties and corrosion resistance was studied. The results showed that the main microstructure of tested steels was tempered martensite and a small number of reversed austenite when specimens were tempered in temperature range of 550-750°C. The variation of mechanical properties corresponded to the austenite volume fraction well. Both the two types of steels displayed a favorable comprehensive mechanical properties after tempering at 650°C, their product of strength and elongation reached to 18.44GPa•% and 18.44 GPa•% respectively. With the best heat treatment process,tempered at 650°C after quenching at 1050°C,the corrosion resistance of 2# steel is more better than 1# steel.

Abstract: Composites made from phenolic resin are filled with conductive filler mixtures containing coke powder and copper powder. They are fabricated by compression molding, followed by post-curing method. The density, electrical conductivity and hardness of composite are analyzed to determine the influence of coke particle size on the physical, electrical and mechanical properties of composite. It is found that there is a marked dependence of the density, electrical conductivity and hardness on coke particle size. The density and hardness decrease with the increasing of coke particle size. However the electrical conductivity increases with the increasing of coke particle size. The increasing of coke particle size from 0-48 µm to 75-180 µm promotes a considerable increase in electrical conductivity by about 204%. The intra-particle conductivity and connectivity of copper particle could be the main reasons for the increasing of electrical conductivity as coke particle size increases.

Abstract: Metastable secondary phase in steel mainly includes sulfide inclusions, rare earth inclusions and nano-scale inclusions or precipitates etc. Many researches indicate that these metastable phases have an important effect on the property of steels. Now, people are going to employ metastable secondary phase to improve the property of steel. Metastable secondary phase in steel usually was studied by metallographic technology in many previous researches because they were destroyed easily by acidic or alkaline reagents during separating from steel. Therefore, the 3-dimension morphology could not be observed through electron microscopes. A method to extract metastable secondary phase in steel using electrolysis technology with organic solution electrolyte is introduced in the paper. Several sorts of metastable phase including MnS, Ce2O3, nano TiN et al are extracted nondestructively by electrolysis with organic solution electrolyte in various steel grades. The 3-dimension morphology, the inside cross-section 2-dimension morphology and composition of these metastable phases are analyzed by scanning electronic microscope (SEM), FE-SEM and transmission electron microscope (TEM). Current research results prove that electrolysis with organic solution electrolyte is an accurate and effective method on preparing sample of metastable secondary phase in steel used to electron microscope analysis.

Abstract: Nickel-plated steel sheet with high ductility and wonderful corrosion resistance, it has been widely used in industry. Stamp forming is a high-volume fabrication method for producing desired components. To determine the optimum values of the process parameters, it is essential to find their influence on the deformation behaviors of the steel and nickel. In this paper, finite element method (FEM) simulation was carried out to analyze some factors such as stress distribution, strain distribution, and fillet radius.

Abstract: Flowing liquid metal corrosion of structural steels in the Pb-Bi eutectic has been synthetically analyzed according to experimental results, mechanics model and aseptic technique. Foregone researches show that element of structural steels have a big influence on the corrosion of structural steels. The increase of temperature induces the increase of corrosion. High Cr steels, high Si steels and covered by the Al films on the steels can effectively defense the corrosion. Through building up the oxidation kinetics and corrosion-oxidation interactions model can be used to better analyze flowing liquid metal corrosion of structural steels in the Pb-Bi eutectic.

Abstract: Fluoride evaporation from Mg slag samples was investigated. F content in the original slag sample from an Mg factory was 1.65%, which decreases to 0.98-1.54% in the samples heated at 1000-1400°C for 3 hours. The values of F evaporation from the test samples were 6.7-40.6%. The fluorides may evaporate in the atmosphere, causing air pollution. Some suggestions were presented based on study results obtained to minimize fluoride emissions and improve environmental performances of the Mg production by using Pidgeon process.

Abstract: Lab-scale germanium co-precipitation with ferric hydroxide in dilute sulfuric acid media was studied. The experiments of co-precipitation of germanium and ferric hydroxide were performed by neutralization of the germanium-ferric sulfate solution via adding calcium hydroxide powder. The variables affecting the germanium precipitation yield were investigated. The experimental results show that high initial germanium concentration, high ferric/germanium molar ratio, high final solution pH, low ion strength and slow temperature will contribute to high germanium precipitation yield.

Abstract: Under strain rate of 0.5s-1, the effect of deformation temperature on flow stress, microstructure and corrosion resistance of 2205 duplex stainless steel (DSS) was investigated. The dynamic recrystallization (DRX) of austenite phase was enhanced with the deformation temperature increasing from 850°C to 1050°C, meanwhile, the leading deformation mechanism changed from work hardening to DRX. When the deformation temperature was further increased to 1250°C, the dynamic recovery (DRV) of ferrite phase played a leading role. The specimen after deformation at 1050°C exhibited better DRX behavior, which leads to more γ/γ grain boundaries and δ/γ boundaries formation, increasing the occurrence of pitting corrosion, and it presented best corrosion resistance at 950°C.

Abstract: This objective is to study the influence of pH on the electrochemical behavior of 00Cr15Ni7Mo2Cu2 supermartensitic stainless steel in 3.5% NaCl solutions using potentiondynamic polarization technique, open circuit potential tests and electrochemical impedance spectroscopy (EIS).The study reveals that the pitting potential (Eb) is higher, the passivation current densities (ip) is lower and the electrochemical impedance increases with the pH. The results indicate that this stainless steel offer good pitting corrosion resistance with the pH increasing in 3.5% NaCl solutions.