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991.
金属氢化物(MH_x)应用于反应堆中子慢化剂、激光离子源片材料、中子发生器用靶时,会经历极端非平衡束流的辐照。本工作提出利用TEMP-6型强流脉冲离子束装置产生的强流脉冲离子束(high intensity pulsed ion beam,HIPIB)辐照Ti D_2膜,评估极端束流对膜力学性能的影响因素和影响程度。采用涂层附着力自动划痕仪、维氏显微硬度计对原始和辐照后的Ti D_2膜进行测试分析。研究结果发现:多次HIPIB的辐照效应导致膜面重熔再结晶,使其内部结构趋于更加致密化和平整化,能降低材料的摩擦系数并在一定程度上提高其初始临界载荷;D的释放有助于膜面韧性、显微硬度的提高,从而减轻了其塑性形变程度。 相似文献
992.
This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before. 相似文献
993.
Aluminum specimens with and without chemically cleaning were welded by electron beam to investigate the effect of、Al 2 O3 film on weld appearance. The removal mechanism of Al 2 O3 film during vacuum electron beam welding of aluminum was analyzed and the effect of Al 2 O3 film on molten pool flow behavior and weld appearance was investigated. The results showed that the weld width of the specimen was enlarged by chemically cleaning. The solid Al 2 O3 film transformed into gaseous Al 2 O via the reaction with liquid aluminum at the temperature higher than 1 350 K was the main reason for the removal of the film. The weld width was narrowed down by the oxide film due to the inhibition of outward flow driven by the surface tension gradient and the drag force between the Al 2 O3 film and liquid Al. The weld penetration was reduced in the initial stage and then enhanced in the metastable stage. 相似文献
994.
合金成分对锆合金焊接区腐蚀时吸氢性能的影响 总被引:3,自引:0,他引:3
采用Fe含量相同,但Cr含量不同的锆合金板与Zr-4板对接焊,腐蚀后不同样品中的氢含量差别很在,与氧化膜的厚度不成比例,说明合金元素Cr对锆合金的吸氢性能有着非常明显的影响,当不含Cr时,焊接样品腐蚀后的氢含量明显减少:Zr.4经不同热处理后Zr(Fe,Cr)2第二相的大小和多少与氢含量有关,说明合金中存在Cr时形成的Zr(Fe,Cr)2第二相是引起吸氢量增加的主要原因。在不含Cr的锆合金中添加合金元素Nb,不仅改善了焊接区的耐腐蚀性能,而且不会引起腐蚀时吸氢增加。氯化锆会在对接焊样品中未焊透的前端析出,这是张应力引起氢的扩散富集并诱发氢化物析出的结果。氢化锆还会沿着熔区边界集中析出,这将影响锆合金力学性能的均匀性。 相似文献
995.
GH4049镍基高温合金疲劳-蠕变行为及形变结构研究 总被引:2,自引:0,他引:2
研究了GH4049镍基高温合金在700℃.±0.45%应变控制条件下的疲劳-蠕变行为,发现合金在循环初始阶段是硬化趋势,随后呈软化趋势,利用透射电镜观察了合金在疲劳-蠕变不同阶段的形变结构,利用会聚束电子衍射技术研究了合金γ/γ’相错配度在疲劳-蠕变中的变化规律,结果表明.γ/γ’相的共格性在形变过程中未受到损失,均匀形变区内,基体位错密度迅速增加,导致合金循环形变初始硬化随形变进行,形变带内γ’相也发生形变,γ’相对基体位错运动阻碍作用降低,形成易滑移通道,合金逐渐软化 相似文献
996.
997.
998.
The decreasing process of oxygen in YBa2 Cu3 O y is investigated through high resolution electron microscopy (HREM) and convergent beam electron diffraction (CBED). Measurements of the axial length in HREM images show that oxygen content y decreases faster near a twin boundary than at the inner part of a twin lamella. The transformation from an orthorhombic to a tetragonal phase starts at a twin boundary and the transformed region propagates to an inner region of lamella. Lattice strains are observed near boundaries between transformed and non-transformed regions. The transformation is almost complete within 30 s during observation of HREM images at 400 kV and at room temperature. A value of y was quantitatively measured by analysing observed intensities of energy-filtered CBED patterns with the dynamical theory. The value of y decreases from 6.9 to 6.5 when 200 kV electrons are irradiated for 160 s in a microscope at 108 K. More precise analysis of the intensities provides information on charge distribution along the c -axis as well as local oxygen content at a spatial resolution of several nanometres. 相似文献
999.
1000.
The concept of shape factors of the fusion-solidification zone is proposed to describe the weld cross section geometry. According to these shape factors, the electron beam weld fusion-solidification zone is divided into four typical shapes and the classification criterion for these typical shapes is suggested. An integrated parameter n, combining the line power density of electron beam and material thermal properties is proposed to describe the relative power input, and another integrated parameter n2 combing the accelerating voltage and focusing current is proposed to reflect the power distribution in the keyhole. A series of new expressions, which can reflect the influence of focusing current, accelerating voltage, beam current, and material thermal properties, are developed to predict the fusion-solidification zone shape based on experimental results nonlinear fitting of n1 and n2. 相似文献