Advanced Materials Research Vols. 560-561

Abstract: The Mechanism of Micropores Formed on the Surface of Polycrystalline Pure Nickel under High-current Pulsed Electron Beam (HCPEB) Irradiation Is Explained. it Is Discovered that Dispersed Micropores with Sizes of 0.1-2.0 µm on the Irradiated Surface of Pure Nickel Can Be Successfully Fabricated after HCPEB Irradiation. the Dominant Formation Mechanism of the Surface Micropores Should Be Attributed to the Formation of Supersaturation Vacancies within the near Surface during the HCPEB Irradiation and the Migration of Vacancies along Grain Boundaries and/or Dislocations towards the Irradiated Surface. it Is Expected that the HCPEB Technique Will Become a New Method for the Rapid Synthesis of Surface Porous Materials.

Abstract: The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed Al-Mn-Si alloy was investigated through TEM observations, anodization metallography, tensile tests and Tafel polarization analysis. High density precipitates were found in the Zn-containing alloys and the alloy with 1.5 % Zn had the most uniform precipitation. The Zn element could restrain recrystallization of the alloy. Tensile test results indicated that Zn has a great effect on tensile strength of Al-Mn-Si alloy. The alloy with 1.8 % Zn addition had the highest ultimate tensile strength. The electrochemical testing results indicated that Zn element had great impact on the corrosion potential of the as-annealed alloys tested in 0.5% NaCl solutions. Alloying with Zn element could make the corrosion potential shift to negative direction but increase the resistance to pitting corrosion

Abstract: Hot continuous rolling technique is a new processing method for preparing Titanium alloy, which may decrease the production cost and realize continuous industrial manufacture. Ti-6Al-4V alloy was prepared by hot continuous rolling (HCR) and solution and aging treated at different temperature. Creep curves of the alloys were measured, microstructure evolution feature of the alloys during creep was observed by SEM and TEM. The influence of aging temperature on the microstructure and creep property of the alloy is briefly discussed. Results show that, the microstructure of HCR alloy after solution treatment at temperature higher than β phase transus point consists of the fully "basket weave" structure. The alloy aged at 750 °C has higher strain rate and shorter creep lifetime, strain rate of the alloy during steady-state creep is measured to be 0.69 × 10-7/s, creep lifetime is measured to be 180h, and strain rate of the alloy aged at 480 °C is measured to be 0.33 × 10-7/s. The alloy aged at lower temperature has longer creep lifetime than the alloy aged at high temperature.

Abstract: An epoxy paint containing PEDOT/PSS was described herein. The corrosion behavior of steel samples coated with the paint was investigated in seawater. For this purpose, electrochemical impedance spectroscopy was utilized and surface morphology of coatings after corrosion was observed using scanning electron microscope. It was found that the addition of small PEDOT/PSS to the epoxy resin increased its corrosion protection efficiency. Meanwhile, the possible mechanism was discussed.

Abstract: This study developed a new polycrystal plasticity model by deducing a set of linear controlling equations with respect to the controlling equation of rate dependent crystal plasticity (RDCP). It was proved numerically efficient and stable by means of the comparison with experiment and an implicit model. The model was then applied to describe earing in deep drawing process. Remarkable effects of rate sensitivity coefficient of the material, drawing speed and dies clearance on earing were found.

Abstract: ReBaCo₂O_5+δ (Re=Pr, Nd, Y) oxides were synthesized by solid state reaction method. The oxygen permeation flux of ReBaCo₂O_5+δ (Re=Pr, Nd, Y) membranes increased with temperature and oxygen partial pressure and ranked as follow: PrBaCo₂O_5+δ > NdBaCo₂O_5+δ > YBaCo₂O_5+δ. The oxygen permeation response of PrBaCo₂O_5+δ membrane was fairly stable and no detectable degradation is observed at high temperature under carbon dioxide conditions (CO₂ = 500 ppm).

Abstract: Anisotropy of CP-Ti sheet in cold deep drawing was investigated by means of experiments. The as-received blank showed remarkable anisotropy due to the existence of the spilt basal texture. Deformation intensified the anisotropy in the distributions of wall thickness and ears, and mechanical properties after drawing. The micro-mechanism causing anisotropy of CP-Ti was analyzed. Then, methods for the improvements of anisotropy were brought out as profile optimization of the initial blank and heat treatment on the finished part at 650 °C for 1 hour.

Abstract: There are many models and failure criteria have been developed to predict the ductile fracture (DF) in metal plastic deformation. But usually, it is difficult to select a suitable model and the corresponding criterion from them. So, finding a way to identity their applicability and reliability is useful for selecting these DF criteria. In this paper, ductile fracture of aluminum alloy A5052P-H34 is studied by experiments and finite element simulations. In experiments, the mode I crack was obtained by uniaxial tension of plate with a circular hole in the center. The von Mises yield model and continuum damage mechanics based Rousselier model and modified Rousselier model are chosen to describe the material behavior. Three failure criteria, including the Cockcroft-Latham integral, maximum shear stress theory and critical void volume fraction criterion are investigated to determine their reliability in ductile failure prediction. These constitutive models and DF criteria are implemented by user material subroutine in ABAQUS/Explicit to predict the crack. And the crack initiation and propagation is implemented by element erosion method. By comparing the experiments and simulations, the modified Rousselier’s model with the corresponding criterion shows agreement with the experiments.

Abstract: Uni-axial tensile test was conducted at room temperature on a weak texture AZ31B magnesium alloy at different strain rate, from 2.8×10-5s-1 to 1.1×10-1s-1. The mechanical behavior was investigated. It was found that as strain rate is increased, flat character of the stress-strain curves can be found and {10-12} tension twinning is responsible for this phenomenon. The sample exhibites a brittle fracture at 1.1×10-1s-1 strain rate while exhibites a ductile fracture character at 2.8×10-5s-1 strain rate.

Abstract: By means of different cooling methods, microstructure observation and X-ray diffraction analysis, an investigation has been made into the influences of the cooling methods on the microstructure and lattice parameters of FGH95 superalloy. The results shown that, after the solution treated alloy is cooled at different mediums, fine γ′phase and carbide particles dispersedly distribute in the grain and coarser γ′phase discontinuously precipitates along grain boundaries. After X-ray diffraction analyzed, the γ and γ′phases in “molten salt cooling” alloy possess larger lattice parameters, and a bigger lattice misfit exists in the interface between the γ and γ′phases.