球罐组焊过程的三维动态仿真模拟

为了分析球罐组焊工艺过程,研究球罐焊后应力分布特点,优化球罐安装过程工艺.以三带球罐为研究对象,根据三带桔瓣式球罐结构特点,建立了三带球罐组焊过程模型.采用移动热源,实现了球罐组焊过程的三维动态模拟.获得了球罐组焊的应力应变场,分别利用直角坐标系和极坐标系对球罐组焊后的变形和应力的分布进行分析,总结球罐残余的各向应力的...     

温度及氢化物对Zr-Sn-Nb合金焊缝疲劳裂纹扩展行为的影响研究

采用小尺寸三点弯曲试样完成了渗氢和未渗氢Zr-Sn-Nb合金母材和焊缝在室温和360 ℃下的疲劳裂纹扩展速率试验,研究了温度和氢化物对焊接薄板的疲劳裂纹扩展行为的影响。结果表明,腐蚀吸氢后,在母材和焊缝区均析出了呈水平向分布的片状氢化物。相比母材区,焊缝区析出的氢化物更为致密。在相同温度下,未渗氢母材的抗疲劳裂纹扩展性能均优于未渗氢焊缝。腐蚀吸氢后,母材在相同温度下的抗疲劳裂纹扩展性能也优于焊缝。在室温下,腐蚀吸氢后的母材和焊缝的抗疲劳裂纹扩展性能相比吸氢前明显下降。360 ℃下,渗氢母材和焊缝中的氢化物部分溶解,使得其抗疲劳裂纹扩展性能得到一定程度提升。     

Compatibility of Austenitic Steel With Molten Lead-Bismuth-Tin Alloy

 The compatibility of the austenitic AISI 304 steel with Pb-Bi-Sn alloy was analyzed. The AISI 304 steels were immersed in stagnant molten Pb-33.3Bi-33.3Sn alloy at 400, 500 and 600 ℃ for different exposure times (100-2000 h) respectively. X-Ray diffraction spectrum (XRD) with a Y-4Q system (CuKα, λ=0.15478 nm) was used to identify the phases on the surface of specimens after exposing to Pb-Bi-Sn liquid metal (LM). The surface and cross section of the specimens were analyzed by means of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The result showed that a FeSn alloy layer on the surface of all specimens was formed, and it prevented AISI 304 steel matrix from penetration attack and loss of alloy elements at 400 and 500 ℃.     

F/M钢包壳管材热处理工艺优化

通过对Fe-12Cr-1.5W-0.2V-0.15Ta F/M钢包壳管材分别进行980~1150 ℃正火和600~730 ℃回火处理,研究不同热处理工艺对包壳管材微观组织、室温力学性能的影响。结果表明,不同温度正火处理后,F/M钢包壳管材的组织均为板条马氏体,随正火温度的升高,粗大的碳化物颗粒逐渐固溶至基体中,且原奥氏体晶粒尺寸会产生粗化,从1050 ℃的40 μm增至1150 ℃的80 μm;不同温度回火后,马氏体基体上析出细小纳米级碳化物颗粒,随回火温度增加,碳化物颗粒析出数量明显增加,但析出的碳化物颗粒尺寸无明显变化;包壳管材经过1100 ℃×60 min正火+650 ℃×90 min回火后具备良好的微观组织和力学性能,其原始奥氏体晶粒无明显长大,马氏体板条组织平均晶粒尺寸约为6.0 μm,小角度晶界比率为59.6%,沿着原奥氏体晶界有纳米相析出,晶内马氏体界面处析出大量纳米相,此时,管材表现出良好的强塑性匹配,抗拉强度为1024 MPa、屈服强度为849 MPa、伸长率为17.3%。     

EBSD investigation on the evolution of microstructure and grain boundaries in coarse-grained Ni–48Al upon large deformation at elevated temperature

The evolution of microstructure and grain boundaries were investigated in coarse-grained Ni–48Al intermetallics during plastic deformation at 1075 °C with the initial strain rate of 1.5 × 10⁻³ s⁻¹ using electron backscatter diffraction (EBSD) technique. Before deformation, most grain boundaries were high-angled (HAGBs), with several particular angles being predominant. During initial deformation, low-angle grain boundaries (LAGBs) with misorientation less than 5° began to evolve. The misorientation of the newly-formed LAGBs increased with the increase of deformation, meanwhile, grain boundaries with misorientations between 6 and 15° were gradually observed, and finally transformed into HAGBs (misorientation angle > 15°). There appeared a steady state transition from the formation of new LAGBs to the transformation into high-angle grain boundaries. As a result, the grain size was refined continuously with the deformation strain.     

I-SCC Behavior Evaluation of N36 Zirconium Alloy Cladding Using Ring Tensile Test

在102,103,104Pa碘蒸气压力和350℃温度条件下对N36锆合金包壳管进行I-SCC(碘致应力腐蚀)环向拉伸试验。对拉断后的环形试样进行宏观观察。碘环境下的试样表现出脆性断口,不同于无碘环境下的杯-杯形韧性断口形貌。分析试验载荷-位移曲线及力学参数,评价试样的I-SCC敏感性。碘环境下力学性能均较无碘环境下降,且下降程度随着碘浓度的升高而增大。通过对I-SCC评价参数的筛选,采用以拉伸载荷-位移曲线下面积表示的韧性作为I-SCC敏感性评价参数,结果表明包壳管韧性随着碘浓度的增加而降低。     

Microstructure evolution and recrystallization behavior of cold-rolled Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy during annealing

The effects of cold-rolling reduction, annealing temperature, and time on recrystallization behavior and kinetics of cold-rolled Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy were investigated using the Vickers hardness test, scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and electron backscatter diffractometry (EBSD). The results show that the rate of the recrystallization increased with increasing annealing temperature and rolling reduction. Recrystallized grains nucleated preferentially at sites with high density dislocation and deformation stored energy and then grew into integral grains. Recrystallization texture changed from $〈10\overline{1}0〉$//RD to $〈11\overline{2}0〉$//RD. The grain orientation changed from random orientation to the orientation with the maximum misorientation around 30°. Recrystallization kinetics and maps were constructed based on the Johnson–Mehl– Avrami–Kolmogorov (JMAK) equation to derive parameters sensitive to the microstructure. The activation energies for recrystallization of 30%, 50% and 70% cold-rolling reductions were determined to be 240, 249 and 180 kJ/mol, respectively.     

Ag-In-Cd芯体辐照后化学成分的计算

Ag-In-Cd芯体的辐照肿胀规律是评价控制棒堆内运行安全性的基础。辐照后Ag-In-Cd芯体的成分变化是引起肿胀的主要物理原因,但目前尚未看到定量计算成分变化的研究报道。本文根据Ag-InCd芯体中各核素的嬗变反应方式和反应截面,建立描述芯体成分变化的微分方程组,编写该微分方程组的数值计算程序,计算预测芯体成分随热中子注量的变化规律。当热中子注量为1.5×1021~6.2×1021 cm-2时,芯体中各元素的含量与热中子注量之间呈较好的线性关系,而芯体表层Sn和Cd的含量会达到中心含量的2倍以上。     

Ag-In-Cd合金辐照后的微观组织变化

Ag-In-Cd合金在核电站压水堆控制棒中广泛使用,其辐照肿胀行为是评价Ag-In-Cd控制棒使用寿命的关键因素。本文通过制备不同成分的模拟合金,来模拟Ag-In-Cd合金在堆内辐照后的成分变化,分析合金的密度及微观组织特点。结果发现,当Ag含量低至77.5%(质量分数)时,合金会分解为fcc和hcp两相,fcc相中贫Sn高Ag,hcp相中富Sn低Ag。当Ag含量在55%~61%之间时,合金以hcp单相存在。由实测的密度拟合出了合金密度随成分变化的关系式。此结果对于理解和掌握Ag-InCd合金的辐照肿胀行为有重要意义。