Effects of Rare Earth on Behavior of Precipitation and Properties in Microalloyed Steels

The influence of rare earths on the behavior of precipitation of 14MnNb,X60 and 10Mn V steels was studied by STEM, XRD, ICP and thermal simulation method. The main carbonitride precipitates are Nb(C, N), (Nb, Ti) (C, N) and V(C, N). In austenite RE delays the beginning of precipitation, and decreases the rate of precipitation. In ferrite RE promotes precipitation and increases the amount of equilibrium carbonitride precipitation. RE can make precipitates fine,globular and dispersed in the microalloyed steels. With the increase of the amount of RE in steel, the amount of precipitation increases. The promotion effect is weakened with excessive RE. RE has only little influence on the strength of microalloyed steel, but it can improve impact toughness effectively.     

Microstructure and Emission Properties of Nanometer Ce-W Material

Nanometer Ce-W material was prepareo by freeze-drying and SPS. SEM and “in situ” AES were used to investigate microstructure, surface behavior and emission properties of material. Compared with micrometer material, the crystal size of nanometer material is smaller. Homogeneous microstructure and uniform distribution of cerium are found in nanometer material. The diffusion ability of Cerium becomes stronger. At high-temperature, the active layer thickens,     

CFD Predictions and Experimental Comparisons of Pressure Drop Effects of Turning Vanes in 90° Duct Elbows

This paper presents new results for numerical predictions of air flow and pressure distribution in two commonly used elbows: (1) 90° mitered duct elbows with turning vanes having 0.05 m radius, 0.038 m vane spacing and (2) 90° mitered duct elbows without turning vanes, in 0.2×0.2?m (8?in.×8?in.) duct cross section using the STAR-CD computational fluid dynamics (CFD) code. A k-ε turbulence model for high Reynolds number and k-ε Chen model were used for that purpose for comparative purposes. The simulation used 13 different Reynolds numbers chosen between the range of 1×105 and 2×106. To validate the CFD results, the results of two experimental papers using guided vanes were compared with simulated vane runs under the same condition. The first experimental study used a 0.6×0.6?m (24?in.×24?in.) square elbow with 0.05 m radius, 0.038 m vane spacing and air velocities at 2.54 m/s (500 fpm) and 25.4 m/s (5,000 fpm), the second experiment used a 0.81×0.2?m (32?in.×8?in.) rectangular elbow geometry with 0.05 m radius, 0.038 m vane spacing with air velocities from 10.16 m/s (2,000 fpm) to 13.97 m/s (2,750 fpm). For Reynolds numbers (1.00–2.00)×105 the pressure drop difference between vaned and unvaned elbows was found to be 35 Pa as compared to 145 Pa. The simulations also agreed reasonably well with published experimental results. For the 0.6×0.6?m (24?in.×24?in.) square elbow and 0.81×0.2?m (32?in.×8?in.) rectangular elbow with vanes, the difference in pressure drop was 3.9 and 4.1% respectively and indicates that CFD models can be used for predictive purposes in this important HVAC applications area.     

Effects of Dysprosium Oxide Doping on Microstructure and Properties of Barium Titanate Ceramic

With the development of mixed integrated cir-cuits , mini mization of high voltage ceramic capacitorcomponents usedin high voltage outletsis required .Inthe past ,the breakdown voltage was raised mainly byincreasingthethickness of capacitors .Butthe most …     

Effects of Rare Earth on Structure and Mechanical Properties of Clean BNbRE Steel

The effects of REinsteel include cleaning,mod-ifyinginclusions and alloying[1 ~4]. With the develop-ment of steel-making and continuous casting process-ing,the fluctuation range of the composition of steelwas mini mized ,the cleanliness of steel was i mpr…     

Effects of Yttrium and Cerium on Compression Properties of Ni_3Al-Base Alloys

The effects of yttrium and cerium on the compression properties of Ni_3Al-base alloys have beeninvestigated.The results reveal that the addition of about 0.1 wt% Y to Ni_3Al-B alloy is effective for improvingthe ductility at 1100℃.A ductility increase of about 100% is observed for this Y doped alloy.The yttrium re-fines grains of the alloy.An YNi_5 phase is found to be precipitated on the grain boundaries in the alloy con-taining 0.3 wt% Yor more.Adding about 0.1 wt% Ce to Ni_3Al-B-Cr-Zr alloy obviously improves the ductilityof the alloy at 1100℃.A ductility increase of about 50% is obtained for this alloy.The added cerium also pre-vents the formation of γ+γ' eutectic and refines it.The bulk phase of CeNi_4 appeares at the front of the eutecticin the alloys containing 0.1 wt% Ce or more.     

Effects of RE and N on Properties of Corrosion Resistance and Oxidation Resistance of Gray Cast Iron

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Effects of Sintering Additives on Microstructure and Mechanical Properties of Hot-Pressed α-SiC Ceramics

In this work, α-SiC ceramics with aluminum or yttria sintering additives ranging from 1.0 to 4.0 wt pct were prepared by hot pressing, and the effect of sintering additives on the microstructure and mechanical properties of SiC ceramics was investigated. Specimens with Al additive exhibited fully dense microstructure with relative density > 99.4 pct. However, the relative density of specimens with Y₂O₃ decreases constantly from 99.5 to 95.7 pct as Y₂O₃ content increases, which is possibly due to the formation of gaseous phase and evaporation of volatile compounds resulting from the chemical reaction between SiC matrix and Y₂O₃ additive. X-ray diffraction (XRD) and Raman spectra results showed that Al addition leads to the transformation from 6H to 4H polytypes, and the transformation degree increases as increasing the Al content, while no obvious polytype transformation is observed for specimens with Y₂O₃ additive. Scanning electron microscopy (SEM) observations revealed that specimens with Y₂O₃ are composed of equiaxed grains with average size about 1.0 μm, whereas the specimens with Al additive exhibit larger grain size with partly elongated grain structure. Additionally, it is found that the grain growth of specimens with Al addition is accompanied by the polytype transformation. Further analysis revealed that, for specimens with Al additive, enhanced grain size and formation of elongated of SiC grains lead to an improvement in fracture toughness from 5.7 to 7.1 MPa m^1/2 but a slight decline in flexural strength from 706 to 632 MPa. The crack deflection and bridging as well as undesirable stress effects related to the large elongated grains are responsible for the variation in mechanical properties. In the case of SiC sintered with Y₂O₃, there are obvious declines in flexural strength and fracture toughness from 714 to 492 MPa and from 5.9 to 3.4 MPa m^1/2, respectively, which are mainly attributed to the increased porosity. The impact of Al and Y₂O₃ on the microstructure and mechanical properties of SiC ceramics was discussed.

     

Effects of RE on Microstructures and Mechanical Properties of Hot-Extruded AZ31 Magnesium Alloy

Effects of rare earth (RE) additions on microstructure and mechanical properties of the wrought AZ31 magnesium alloy were investigated. The results show that, by adding 0.3%, 0.6% and 1.0% RE elements, the as-cast microstructure can be refined, and the as-cast alloys‘ elongation and tensile strength can be improved. After extrusion, the alloy with 0.3 % and 0.6% RE additions obtain a finer microstructure and the best mechanical properties, but the alloy with 1.0% RE addition has the coarse A1-RE compound particles in grain boundaries which decreased elongation and tensile properties. Usually, Rare earth (RE) elements were used to improve the creep properties of aluminium-containing magnesium pressure die cast alloys at elevated temperatures. In this paper, it is also found that the high temperature strength of extruded materials can be increased by RE elements additions.     

Understanding the Material Flow Mechanisms—Microstructure Evolution—Defect Formation Relationships and Effects on Mechanical Properties in Friction Stir Welding of Dissimilar Aluminum Alloys

Metallurgical and Materials Transactions A - The material flow mechanisms in large-thickness dissimilar friction stir welds have been determined in this study by systematically investigating the...     

Effects of Austempering and Martempering Processes on Amount of Retained Austenite in Cr-Mo Steels （FMU-226） Used in Mill Liner

The presence of retained austenite gives rise to deterioration of the wear resistance and fracture strength of Cr-Mo steels in many cases. Thus, the effects of heat treatments including direct quenching, martempering, and austempering on the retained austenite existing in the microstructure of these steels were investigated. Specimens were austenized at 950 ℃ followed by direct quenching using compressed and still air. The specimens were also isothermally quenched in salt bath at 200 and 300 ℃ for 2, 8, 30, and 120 min. Microstructures of the specimens were studied using optical microscope (traditional black and white etching as well as color etching), scanning electron microscope (SEM), microhardness tester, and X-ray diffraction (XRD). The results showed that the lowest amount of retained austenite in the microstructure was obtained in the specimens quenched isothermally at 300 ℃ for 120 min.     

Effects of Nd Doping on Magnetic-Optical Properties of GdFeCo Thin Films

The GdFeCo and NdGdFeCo thin films were prepared by sputtering, and their hysteresis loops, the temperature dependence of the saturation magnetization Ms and the magneto-optical Kerr spectrum in the visible light range were measured. By studying the effects of light rare earth element Nd doping on the magneto-optical Kerr rotation angle of GdFeCo thin films, it is found that proper Nd additives in GdFeCo films could enhance Kerr rotation at short wavelengths. So it could be better medium used as the readout layer of center aperture detection magnetically induced super resolution （CAD-MSR）.     

Effect of V–Nb Composite Microalloying on Microstructure and Properties of Non-Quenched and Tempered Forged Steel

Herein, non-quenched and tempered forging steels containing V and V–Nb are designed, and the mechanical properties and microstructure of two steels are compared and analyzed. The comprehensive mechanical properties of V–Nb containing steel are as follows: the yield strength is 525.1 MPa, the impact energy A_kV is 62.1 J at ambient temperature, and the elongation is 26.1%. It is shown in the results that the addition of Nb element can refine the grain size (17.2 μm), increase the ferrite content (54.1%), and refine the lamellar spacing of pearlite (274 nm). The formation of V (C, N) particles on MnS inclusions can promote fine ferrite nucleation and growth, and Nb element can further promote ferrite nucleation by forming coarser (V, Nb) (C, N) particles. The difference of yield strength and hardness between the two steels is mainly caused by the difference of precipitation strengthening, the precipitation-strengthening increment of V–Nb containing steel is 18.31 MPa higher than that of V containing steel, which is because the coarser-size (V, Nb) (C, N) particles produce stronger precipitation-strengthening effect. But the large-sized MnS inclusions are beneficial to the increase of crack driving force and reduce the plasticity and toughness.     

Effects of Thermalrate Treatment Technique on Microstructure and Mechanical Properties of Hypoeutectic Al–Si Alloys

In this study, effects of thermalrate treatment (TRT) technique on microstructure and mechanical properties of hypoeutectic Al–Si alloys with addition of Ti were studied. The superheating temperatures of the melt were ascertained based on the DSC result. The results show that when the alloy castings in sand mold were treated with TRT technique at the superheating temperature of 930 °C, α-Al changes into smaller equiaxial crystals from coarse dendrites, and hardness of the alloy increases by 12.7 %, compared to that of the alloy treated with conventional casting technique. In addition, the supercooling increases to 8.5 °C and the characteristic temperatures of eutectic solidification are all the lowest with TRT technique at the superheating temperature of 930 °C. As holding time increases at the pouring temperature of 730 °C in TRT at the superheating temperature of 930 °C, the effects on microstructure and mechanical properties of the alloy casting in sand mold decrease. TRT technique plays a limited role in the alloy casting in permanent mold.     

Effects of Trace Additions of Magnesium on Microstructure and Properties of Fe–36Ni Invar Alloy

Low-thermal-expansion alloys play a crucial role in high-precision instruments and devices. Simultaneously improving mechanical performance and keeping or even decreasing low thermal expansion behavior are urgently required for their industrial application. Herein, a new attempt to treat Fe–36Ni Invar alloy by adding trace magnesium (Mg) in a concentration ranging from 0 wt% to 0.0030 wt% (similarly hereinafter) is conducted. The introduction of Mg results in grain refinement and an increase in the volume fraction of the annealing twins. Compared with the Mg-free sample, the coefficient of thermal expansion (CTE) of 0.0030% Mg alloy is significantly decreased by more than 20%, which is mainly related to lattice distortion and matrix purification. The yield strength of 0.0030% Mg alloy improves by 10% with respect to Mg-free alloy, because of grain boundary strengthening and solid-solution strengthening. The study may lay the basis for a better understanding of the application of Mg in low-thermal-expansion alloys.     

Effects of La-Rich Rare Earth Alloys on Structure and Mechanical Properties of ZL101A Alloy

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Effects of γ-irradiation and Deformation Temperature on Tensile Properties of Pb-2 mass% Sb Alloy

Effects ofγ-irradiation and deformation temperature(T)on the tensile properties of Pb-2mass% Sb alloys were studied.The samples were annealed at 458 Kfor 2hin air,then water quenched after they wereγ-irradiated(the different doses were 0.5,1.0,1.5,and 2.0 MGy).The tensile properties were performed using stress-strain measurements at a constant strain rate(1.2×10~(-3) s~(-1))and at different T(303-393K).It was found that at constant dose,the fracture stress(σF)decreases while the fracture strain(εF)increases as Tincreases.At particular T,σFincreases whileεFdecreases with increasing dose.The strain-hardening exponent(n),which is the slope of the relation between ln(σ)and ln(ε)of the parabolic part of the stress-strain curve,was determined and its values increase as Tincreases and decrease as the dose increases.The value of the activation energy increases as the dose increases from 0.07 eV for un-irradiated sample to 0.1eV for the 2 MGy-irradiated sample.These values are in accordance with that needed for dislocation movement and ordering process.An interpretation of the results was given,based on the creation of point and line defects due toγ-irradiation,and that results in a distribution of beta phase(Sb-phase),leading to a difficulty in the movement of dislocations,so there is an increase in alloy hardness.