Abstract: The deformation behavior in isothermal compression of Ti-5Al-4Mo-2Cr-4Zr-2Sn-1Fe alloy was investigated at the deformation temperature of 800°C, 850°C, 900°C, 950°C and 1000°C, the strain rate of 0.01s-1, 0.1s-1, 1.0s-1 and 10.0s-1, and the height reduction of 70%. The flow stress increases rapidly with the increasing of strain at the beginning of deformation. When the strain exceeds a certain value, the flow stress begins to decline and becomes steady. With the increasing of deformation temperature and decreasing of strain rate, the steady stress and peak stress decrease significantly. The effect of strain on the processing maps of Ti-5Al-4Mo-2Cr-4Zr-2Sn-1Fe alloy is obvious. As the strain increases, the instable region moves towards high temperature and high strain rate area. Meanwhile, the contour of efficiency of power dissipation becomes more and more intensive, and the region with high efficiency of power dissipation reduces. Strain rate of 0.01s-1 and deformation temperature of 900°C are the optimum processing parameters for Ti-5Al-4Mo-2Cr-4Zr-2Sn-1Fe alloy forging under strain of 0.3.
Abstract: The fatigue life of 7050 Al alloy samples after different surface treatments, i.e., as-machined, anodizing, shot peening, and shot peening followed by anodizing, had been tested. The shot peening treatment specimens presented the longest average fatigue life. The fatigue life of anodizing treatment specimens decreased by 69.3% and 78.8% at 215 MPa and 260 MPa stress levels than as-machined ones. Introducing the shot peening treatment before anodizing can increase the fatigue life by 220% / 296.9% at 215 MPa/260 Mpa than that only treated by anodizing. The effect of the surface treatments on the fatigue life were studied by performing surface morphology investigation, residual stress measurements and fracture surface analysis.
Abstract: In order to improve the composition and microstructure of nickel-base single crystal superalloys, equilibrium phases of third generation single crystal superalloys RenéN6 and CMSX-10 have been researched by using thermodynamic calculation software JMatPro. The calculated results indicated that the two superalloys have the same equilibrium phases, such as liquid phase, γ phase, γ’ phase and TCP (topologically close-packed phases), however, there are differences in the quantity and temperature range. RenéN6 alloy has higher content of μ phase. And CMSX-10 alloy has higher γ’ phase precipitation temperature and more γ’ phase precipitates.
Abstract: Dendrite growth of Ni-0.4083%Cu alloy was simulated by the phase-field method in the paper. The impact of super-cooling degree and super-saturation degree and solute segregation on dendrite growth was studied systematically. solute segregation increased initially then tended to decrease. The increase of super-saturation can promote the growth of lateral branch and destroy the constancy of the dendrite tip at the same time. The simulation result was compared with the microscopic theory and they have a good agreement.
Abstract: Refractory high-entropy alloys (RHEAs) have outstanding characteristics such as high melting point, high temperature oxidation resistance and corrosion resistance, which shows very promising application in the high temperature field; but commonly the refractory high-entropy alloys have the disadvantages of high density and poor plasticity. In this work, ZrTiHfV0.5Nb0.5Cx (x=0, 0.06, 0.12, 0.2) alloys are prepared by vacuum non-consumable arc-melting with ZrTiHfV0.5Nb0.5 based. The density of ZrTiHfV0.5Nb0.5C0.2 alloy is reduced to 8.014g/cm3 compared to ZrTiHfV0.5Nb0.5 (8.135g/cm3). The microstructure, static and high-temperature compressive strength are investigated. XRD and EDS analysis show that the microstructure of ZrTiHf0.5Nb0.5Cx alloys consists of BCC phase and HfC phase. ZrTiHfV0.5Nb0.5Cx alloys have high compression plasticity with plastic strain> 40% at room temperature, no fracture occurred during compression and yield stress is closed to 1GPa.
Abstract: Microstructures, phase stability and properties of the as-solidified CoCrCu0.5FeNi(Si/B)x alloys were studied in this work. Intermetallic compounds are found when Si or B was added in a FCC structural CoCrCu0.5FeNi high-entropy alloy, and B possess a better intermetallic formation ability than Si. On the other, solute ability of Si is better than that of B in CoCrCu0.5FeNi alloy. The strength of CoCrCu0.5FeNi high-entropy alloy was improved after the addition of Si and B, and the strengthen mechanism was discussed. Moreover, parameter g can provide a reference to predict the ability of forming intermetallic compounds in CoCrCu0.5FeNi(Si/B)x alloys. The increase of δ is prone to the forming of intermetallic compounds. But the volume fraction of intermetallic compounds increase with the decrease of Ω in the same alloy system.
Abstract: In this paper, we studied the element diffusion behaviors of the multi-principal CoCrFeNi high entropy alloy in molten Al at 700°C. Microstructure, structure and microhardness in the diffusion interfaces of CoCrFeNi and Al are studied by the X-ray diffraction, the scanning electron microscopy, the energy spectrometry, and the microhardness tester. The results showed that a complex chemical reaction occurred at the interface between the high-entropy alloy and the Al. A mixture of FCC + BCC solid solution layer was first formed. Then a bulk Al13Cr2 compound formed near the Al of the solid solution layer. With the increase of dipping time, the thickness of the solid solution layer remained unchanged, and the compounds gradually changed into spheres distributed in the Al matrix. The formation of BCC structure makes the hardness of the solid solution layer up to 450HV, and the existence of the compound also increases the hardness of the Al matrix significantly.
Abstract: In this paper, a new type of multi-principal component Ni5Cr4WFe9Ti pre-alloyed spherical powder was designed and prepared. The method of selective laser melting (SLM) was used to fabricate the testing coupons, so that the Ni5Cr4WFe9Ti samples were prepared successfully. The preliminary processing parameters were determined by the energy density derived from Rosenthal model, combining the different processing parameters (e.g. laser power P, scanning speed V and scan scape), and the range of optimum processing parameters was obtained by orthogonal tests. The effects of energy density on the microstructure and mechanical properties of the materials were studied by XRD, SEM, DSC and room temperature static tensile tests. The results showed that the materials had a single phase FCC structure with good thermal stability, the melting point was 1418.9 °C, and there is no phase transformation until 1265.9 °C. The tensile strength, yield strength and plasticity were 981MPa, 733MPa and 16.1% respectively, which increase by 31.15%, 110.03% and 69.47%, respectively comparing to the as-cast samples,. These results demonstrate that SLM provides a new path for the additive manufacturing to fabricate multi-principal component alloys.
Abstract: The present study investigated the effect of cold rolling reduction on microstructure and mechanical properties of a 204C2 Cr–Mn austenitic stainless steel which contained 16%Cr, 2%Ni, 9%Mn and 0.083 %C). The 204C2 austenitic stainless steels were cold rolled at multifarious thickness reductions of 10%, 20%, 30%,40% and 50%, which were compared with the solution-treated one. Microstructure of them was investigated by means of optical microscopy, X-ray diffraction technique and scanning electron microscopy. For mechanical properties investigations, hardness and tensile tests were carried out. Results shows that the cold rolling reduction induced the martensitic transformation (γ→α ́) in the structure of the austenitic stainless steel. With the increase of the rolling reduction, the amount of strain-induced martensite increased gradually. Hardness, ultimate tensile strength and yield strength increased with the incremental rolling reduction in 204C2 stainless steels, while the elongation decreased. At the thickness reduction of 50%, the specimen obtained best strength and hardness. Hardness of 204C2 stain steel reached 679HV. Ultimate tensile strength reached 1721 MPa. Yield strength reached 1496 MPa.
Abstract: Grain-oriented silicon steel was produced by strip casting route. The effect of different annealing temperature on primary annealing and secondary annealing was investigated. The result showed that the average grain diameter increased and the grain uniformity was gradually destroyed with the increasing annealing temperature. Regardless of annealing temperature, the primary texture consisted of strong γ-fiber and weak λ-fiber. With the increase of annealing temperature, the γ-fiber intensity increased. In addition, the Goss component was not shown at 780-880 °C but appeared at 980 °C. After secondary annealing, complete abnormal grain growth occurred in all samples and the average grain diameter increased with the primary annealing temperature. The Goss sharpness of secondary grains firstly increased and then decreased with a peak value obtained at 830 °C. This result was explained in terms of the combination of the inhibiting force, primary grain diameter and primary texture.