Papers by Keyword: Precipitate

Abstract: The microstructure and mechanical properties of Al-Zn-Mg alloys with low Zn/Mg ratios have been studied.According to various researchers, the major strengthening is due to η-phase and T phase. There are many briefly research on the microstructure and interface of the η-phase types but not briefly information about the T-phase That’s why now our aim to work on T-phase. In actual our aim is to observe the T-phase interface. The MgZn₂ phase (η phase) and its metastable phase (η′ phase) were the most prominent precipitates. Another study revealed various Mg₃₂(Al, Zn)₄₉ phases (T phase) and their metastable phase (T′ phase) in Al-Zn-Mg alloys with low Zn and high Mg content. Al-Zn-Mg alloys with a Zn/Mg ratio of 0.71 were explored for this study. The alloy with a Zn/Mg ratio of 0.71 aged at 473k for 2000 minutes exhibited the highest hardness, according to the observations. The strengthening precipitates in the investigated alloy were totally T′ phase, according to TEM observation.

Abstract: Effect of grain boundary morphology on ductility dip cracking (DDC) sensitivity of nickel base alloy inconel52 deposited metal was researched by welding thermal simulation method and high temperature tensile test. The sample was hold at 1300 °C for 2S ~ 10s and then stretched at its DDC sensitive temperature 1050 °C at different tensile rates. The DDC sensitivity was compared by reduction of area (VoA) of tensile test sample. The results show that straight grain boundary reduces VoA, precipitates in grain boundaries increases VoA, and VoA increases with the increase of tensile rate. Straight grain boundary causes stress concentration and strain localization at the trigeminal grain boundary, curved grain boundary decreases the maximum Mises stress which make more uniform stress distribution. Precipitates on the grain boundary can play a role of locking the grain boundary migration and disperse the strain concentration at the trigeminal grain boundary. The lower the strain rate, the longer the deformation time, which will lead to decrease of dislocation movement rate. The smaller the critical shear stress of grain boundary sliding, the smaller the deformation resistance, and the full progress of dislocation movement and climbing. Effect of strain rate on DDC needs more research.

Abstract: In the actual industrial production process, it is usually appropriate to reduce the cooling rate and control the residual stress. In this study, the Time-Temperature-Property curve of Al-Mg-Si alloy sheets was measured by interruption quenching and subsequent artificial aging method. The microstructure evolution of Al-Mg-Si alloy was carefully characterized using optical microscopy (OM) and transmission electron microscopy (TEM). It was found that the nose temperature of the TTP curve drawn by experiment was ~360°C, closing to the nose temperature of ~365°C obtained from the simulated TTT curves. The number of equilibrium phase rapidly increased with the increasing of holding time, while no obvious equilibrium phase formation at the low temperature region and high temperature region. The critical cooling rate is 14.3°C/s, the determination of the critical cooling rate has important reference value for the control of alloy sheet during quenching process in the actual industrial production. The quenching sensitive region of the Al-Mg-Si alloy sheet is between 290°C and 440°C.

Abstract: The effect of solution treatment temperature on the microstructure, phase present and hardness on Fe-33Ni-19Cr alloy was study in this work. The Fe-33Ni-19Cr alloy was experienced a solution treatment process at six different temperatures which are 950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C and 1200 °C for 3 hours soaking time followed by water quench. The average grain size was measured by using linear intercept methods ASTM E112. Microstructure of solution-treated Fe-33Ni-19Cr alloy was characterized by using optical microscope and scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) spectrometer. The phase present was analyzed using x-ray diffraction (XRD) technique. The Vickers hardness was used to measure the hardness of solution-treated Fe-33Ni-19Cr alloy. Increasing the solution treatment temperatures were increase the average grain size of solution-treated Fe-33Ni-19Cr alloy. In addition, all samples exhibited an equiaxed matrix grain with slight distribution of precipitates particles. The hardness of solution-treated Fe-33Ni-19Cr alloy was decrease as the solution treatment temperature increase.

Abstract: The effect of the second-stage aging process on the tensile properties, fracture toughness and electrical conductivity of 7050 aluminum alloy die forgings was studied, and the mechanism of strengthening and toughening was analyzed by transmission electron microscope and scanning electron microscope. The results show that with the extension of the second-stage aging time, the morphology of the precipitation phase remains unchanged, but the average radius of the precipitation phase and the distance between each other gradually increase. The fracture modes at this aging temperature are mixed fracture mechanisms of dimple fracture and intergranular fracture, and the number of dimple fractures increases with time. With the extension of the second-stage aging time, the strength of the alloy decreases, and the fracture toughness and stress corrosion resistance increase. The alloys heat-treated at 120°C×6 h +177°C×6~8 h two-stage aging process have excellent comprehensive properties.

Abstract: In most scenarios, there tend to have some impurities such as organic and inorganic substances found on the surface water. These impurities can be classified as insoluble and soluble compounds which in turn, can be purified by filtration and sedimentation prior used. Calcium carbonate (CaCO₃), is one of the most contaminated compounds on surface water, mainly causes severe damage to industrial parts. Therefore, CaCO₃ need immediate removal from raw water before applied to an unit operation by coagulation and flocculation. We mainly focused on precipitation of synthetic water and raw water with polyaluminium chloride (PAC) and synthetic polymer flocculants in this research study. The synthetic flocculants of Polyacrylic acid (PAA), Polyacrylamide (PAM) and Poly (acrylic acid-co-acrylamide) (PAAAM) by free radical polymerization in aqueous. The PAAAM is synthesized in various mole ratio of acrylic acid and acrylamide of 9:1 to 5:5. The polymer flocculants are characterized by FT-IR and ¹H-NMR techniques. The FTIR spectra of the sample showed absorption frequency above HYPERLINK "tel:3200-3000" \t "_blank" 3200-3000, 1750-1550 and 1650-1500 corresponding to OH and CO stretching and NH bending respectively. The ¹H-NMR spectra of PAM showed chemical shift at 1.50, 2.10 and 4.20 ppm regarding to proton of methyl, methylene and amide group respectively and the present of proton resonances at 1.50 and 2.30 ppm regarding to proton of methyl and methylene of PAA. The removal efficiency of suspended CaCO₃ is measured and calculated via turbidity technique. The dosage of PAC 0.1 ppm can remove suspended CaCO₃ approximately 65.33% after the PAAAM with mole ratio of 8:2 is applied to system lead to the removal efficiency increasing to 99.03%.

Abstract: Co-Cr-Mo alloys is the material used as a biomedical implant in human body. This material is widely used because they have excellent in corrosion and wear resistance. In this study, microstructure and results of tensile test that were affected by carbon and nitrogen were investigated. The specimens of Co-Cr-Mo alloy were made by investment casting. The compositions of the alloys are Co-28Cr-6Mo-0.8(Si, Mn, Fe)-0,2Ni-(0.08-0.25)C-(0-0.2)N. After that process, microstructure of the alloys is characterized by, SEM/EDX and XRD testing using bulk and electrolytic extracted specimens. The mechanical properties were determined by tensile test. The precipitate content in as-cast alloys was higher when carbon and nitrogen was added. The main precipitate formed in the specimens with variations in carbon and nitrogen is M₂₃X6 type, π-phase, χ-phase, and σ-phase. Carbon and nitrogen promoted M₂₃X₆ type and π-phase precipitation, respectively, meanwhile χ-phase was formed in the alloys with low carbon content. The addition of carbon and nitrogen shows an increased in yield strength, tensile strength and elongation of as-cast Co-28Cr-6Mo-0.8(Si, Mn, Fe)-0,2Ni-(0.08-0.25)C-(0-0.2)N alloys.

Abstract: Water resistance of lauric acid (L) dissolved in biocompatible solvents mainly depended on the water affinity of solvent. L in DMSO (DL) was most sensitive to water and higher than L in N-methyl pyrrolidone (NL) and L in 2-pyrolidone (PL), respectively. From scanning electron microscope, differential scanning calorimetry, thermogravimetric analysis, powder x-ray diffractometry and hot stage microscope tests revealed the alteration of L crystal owing to the interference by solvent during precipitation. All L precipitates had lower melting point and degradation temperature than intact L in which L precipitated from 2-pyrrolidone exhibited the lowest melting temperature. These characteristics will be useful for modifying L in phase inversion in situ forming gel.

Abstract: A study was carried out to determine the deform behavior in a polycrystalline Ni-based superalloy based on micropillar compression tests. Three different heat treatments of this alloy were evaluated by systematically controlling the cooling rate from the supersolvus solutioning step, in order to examine the effect of γ' microstructure on the CRSS (Critical Resolved Shear Stress). It is shown that the γ' precipitates have the marked effect on the deform behavior of micropillar, as the size of the secondary γ' in the general microstructure decreased, the CRSS were increased; SEM and TEM examination show that compressive deformation behavior of [110] oriented micropillars is dominated by dislocation plasticity. Cross slip is occurring in different slip planes, and exhibits away slip lines as well as stacking faults across γ/γ' microstructure. The γ' and carbides in this alloy effectively impeded the motion of dislocations and inhibit the strain burst behavior, caused by the running out of dislocations to the surface of micropillars,which leads to the sustained strain hardening the plastic deformation stage of micropillars.

Abstract: The combined strengthening effect of grain refinement by equal channel angular pressing (ECAP) and aging on a wrought Mg-12Gd-3Y-0.5Zr (mass fraction, %) alloy was investigated. The resulting mechanical properties and microstructures were examined by uniaxial tensile test, optical microscope (OM) and transmission electronic microscope (TEM). It is found that ECAP for 4 passes at 673K followed by aging treatment at 523K for 16h is the optimum condition to strengthen the selected alloy Microstructure analysis reveals that precipitates appear at grain boundaries, accompanies by a few precipitates in grain interior after ECAP and aging treatment. By contrast of as-annealed sample, the strength and elongation were improved which revealed that grain boundaries and precipitation hardening were the main contributor to the high tensile strength of the experimental alloy.