Papers by Keyword: Second Phase

Abstract: In this study, the 38MnSiVS medium carbon non-quenched and tempered steel bar was investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and quantitative metallography. The microstructures were mainly composed of ferrite and pearlite. The phase transition-microstructure prediction models were established to calculate ferrite volume fraction f_α, ferrite grain size d_α and pearlite interlamellar spacing S_o. The volume fraction of the second phase V (C, N) was calculated by thermodynamics. The morphology of the second phase V (C, N) was observed by TEM, and the distribution of particle size of the second phase was determined. And the mechanical properties were measured. Considering the microstructural parameters (f_α,d_α and S_o), the modified coefficient of solid solution elements, and the effect of precipitates, combining with some reference models, prediction model of mechanical properties including yield strength, tensile strength and impact toughness were finally established.

Abstract: The structure, texture, second phase and magnetic properties of non-oriented electrical steel with cold and heat slab were comprised through the production test. The research result shows that the grain size of hot rolled plate by cold slab is less than that of hot rolled plate by hot slab. But after cold rolling and annealing process, the grain size is consistent. Microstructure of hot rolled coil is recrystallized microstructure and the dispersion degree of texture orientation is high. Deformation makes the texture enhancement in cold rolling which become the strong texture based on {001} {111} and <110> texture. The Ti element has aggregation which can form hard impurities as TiN and TiSN to obstruct the recrystallization. Micro fine TiC formed in the annealing process which would block magnetic domain movement and reduce the magnetic properties of the product. MnS is precipitated impurities and the coarsening of MnS phase can reduce the domain block by improving the continuous annealing temperature and the magnetic field would be optimization.

Abstract: The electrochemical properties of Al-Zn-Ga-In-(Pb/Bi) anode alloy are studied by electrochemical test, including constant current test, polarization curve test, AC impedance test. Metallographic microscope is used to observe the microstructure of the alloy . energy spectrum technical is used to analyze the second phase elements. The results showed that the adding of element Pb or Bi both can attain more negative open-circuit potential; the adding of Bi makes the working potential shift positively, and reduces the current efficiency; 2% Pb content can attain more negative working potential, and current efficiency are increased slightly; the series anode the morphology of dissolution relatively uniformly in 3% NaCl solution; anodic polarization are all relatively smaller than cathodic polarization, and they have good anodic polarization properties. The overall electrochemical properties of Al-3Zn-0.015Ga-0.025In-2Pb alloy are the best in these five aluminum alloy anode.

Abstract: Friction stir welded butt joints on 2024T3 alloy have been obtained using two different process regimes. The microstructures of all the weld joint zones have been examined and such structural parameters as grain size, particle size and volume content of particles have been determined in order to find correlations with the microhardness of the corresponding zones.

Abstract: The Mg-(4,6)Zn-1Ca-1RE-0.5Mn magnesium alloy sheets were processed by hot rolling, and the effect of Zn concentration on the microstructure and mechanical properties was investigated using OM,SEM and XRD technique. The Mg-4Zn-1Ca-1RE-0.5Mn sheet exhibits excellent tensile properties at ambient temperature with ultimate tensile strength of 332MPa and elongation to failure of 4.5%. The notable mechanical properties were attributed to fine DRX grains and large deformed grains with intense basal texture.

Abstract: Heat-resistant Al-8.5Fe-1.3V-1.7Si aluminum alloys were prepared by spray forming technique. The phase transition of deposited alloys from room temperature to 500°C was measured by Differential Scanning Calorimeter. The organization and the second phases of the alloys were observed and studied by transmission electron microscopy. The research results show that No endothermic peak appears in the deposited alloys during heating process, there is no phase transition occur in the alloy during the heating process from room temperature to 500°C. The deposited alloys mainly include α-Al and α-Al₁₂(Fe,V)₃Si phase. Under the transmission electron microscopy, there are also a small amount of slug, fan-shaped, needle-like, block, strip second phases, these phases are Al₁₂Fe₃Si, Al₈Fe₂Si, θ-Al₁₃Fe₄, Al₉FeSi₃, Al₆Fe.

Abstract: Microstructure of Mg-9Zn-xAl (x=2,4,6) magnesium alloy was prepared by traditional casting, SIM casting and isolated treatment. The effect of Al content addition on microstructure of Mg-9Zn-xAl was investigated. Results show that Compared with traditional casting, grain size is refined by self-inoculation method casting. Grain size of Mg-9Zn-xAl (x=2,4,6) is 88μm,76μm and 69μm respectively at traditional casting, and is 49.5μm,42μm,35.6μm respectively at SIM casting. With Al content increase, the isolated island-like secondary phase change into semi-continuous network and continuous network, and combination between Magnesium and alloy element decrease accumulation of magnesium atom on the primary phase, so that the growth of the primary phase is prevented.

Abstract: An Mg-10Gd-3Y-0.4Zr alloy (GW103K) was processed by equal-channel angular pressing (ECAP) for 1-6 passes at 663 K; and the evolution of microstructure during ECAP was studied by OM and XRD. After ECAP, the grain size was reduced from 65 μm (initial state) to 4.2 μm (6 passes), the β equilibrium phase precipitated gradually and the area fraction of β phase increased from 0.8% to 13.4%. The distribution of fine grain zones and second phase particles were coincident, which was consistent with PSN. During the ECAP process, the yield strength increased up to a peak and then decreased, and the elongation increased firstly, then decreased later and increased again. The optimal mechanical properties were obtained after 3 passes, which was attributed to the combined effect grain refinement and second phase particle strengthening.

Abstract: In this paper, a new biomedical Mg-Li alloy for the improvement of the comprehensive mechanical properties by micro-alloying and processing to meet the need of mechanical properties of biomedical materials. And the Mg-Li (Mg-Li-Al-Zn-Ca-Sr) alloy's processing and heat treatment were investigated in detail. The crystal texture of cast state, forged state and rolled state were observed and analyzed by OM, XRD and SEM. The mechanical properties of every stage were tested as well. The results showed that the grain size was refined obviously by the concentrating of Ca and Sr in the grain boundary. With the increase of rolling lane, the second phase's distribution was changed to a scattered state gradually from the reunion state. The tensile strength of the forged alloy was improved as well as its elongation after cold rolling and with rolled heat treatment process. The tensile strength reached 220MPa and the elongation reach 22%, which might meet the demand of cardiovascular stents mechanics.

Abstract: Research on multipass plastic deformation of 7A04 ultra-high strength aluminium alloy by isothermal compression experiments on the 6300KN extrusion press. Experiment results show that elongation reaches its maximal value 9.25% after the first deformation. It is obvious that fibrous tissues appeared along the metal flow direction in the deformed 7A04 ultra-high aluminium alloy, with heterogeneous distribution of precipitated η (MgZn2) phase in the matrix, which results in lower strength (Rm=335MPa, Re=212.5MPa). As the times of deformation increases, precipitated phases grow gradually and the plasticity of alloys decreases dramatically, which reaches its minimal value 5.17% after the fourth deformation. With η(MgZn2) phase disperses gradually, the strength of the alloy increases gradually, and reaches its maximal value 386.7MPa after the fourth deformations. It is proved that 7A04 high-strength aluminium alloy has better synthetic mechanical properties after four times deformation.