Microstructural and mechanical properties assessment of transient liquid phase bonding of CoCuFeMnNi high entropy alloy

The transient liquid phase (TLP) bonding of CoCuFeMnNi high entropy alloy (HEA) was studied. The TLP bonding was performed using AWS BNi-2 interlayer at 1050 °C with the TLP bonding time of 20, 60, 180 and 240 min. The effect of bonding time on the joint microstructure was characterized by SEM and EDS. Microstructural results confirmed that complete isothermal solidification occurred approximately at 240 min of bonding time. For samples bonded at 20, 60 and 180 min, athermal solidification zone was formed in the bonding area which included Cr-rich boride and Mn₃Si intermetallic compound. For all samples, the γ solid solution was formed in the isothermal solidification zone of the bonding zone. To evaluate the effect of TLP bonding time on mechanical properties of joints, the shear strength and micro-hardness of joints were measured. The results indicated a decrement of micro-hardness in the bonding zone and an increment of micro-hardness in the adjacent zone of joints. The minimum and maximum values of shear strength were 100 and 180 MPa for joints with the bonding time of 20 and 240 min, respectively.     

高强钢焊接箱形截面压弯构件局部稳定试验研究

为研究高强钢压弯构件的局部稳定性能,对5个Q460C和5个Q690D钢焊接箱形截面构件进行了单向偏压试验,分析了其破坏形式、局部稳定性能以及承载力;将实测承载力与欧洲规范EN 1993-1、我国标准GB 50017—2017和美国规范ANSI/AISC 360-16相关公式计算结果相比较,以验证各规范对Q460C钢和Q690D钢焊接箱形截面压弯构件屈曲后强度计算的适用性。研究结果表明：所有高强钢焊接箱形截面压弯构件均在柱中附近发生局部屈曲破坏;由轴向压力-轴向压缩变形或轴向压力-水平位移曲线可知,其为极值点失稳;构件的轴向压力-水平位移或轴向压力-应变曲线的形状和局部屈曲模式有关;在翼缘宽厚比为28.1～56.3、腹板高厚比为40.2～80.4、偏心距为20～50 mm范围之内,EN 1993-1和GB 50017—2017中的屈曲后强度计算公式仍然适用于Q460C和Q690D钢焊接箱形截面压弯构件,而ANSI/AISC 360-16中的相关公式需要进一步修正。     

箱形截面柱剪力键式全螺栓连接受力性能研究

为了解决传统箱形截面柱法兰连接节点对结构空间占用的问题,提出了一种箱形截面柱剪力键式全螺栓连接节点,并对2个全螺栓连接箱形截面柱和1个整体式箱形截面柱进行拟静力试验研究。观察了全螺栓连接箱形截面柱的破坏现象,分析了全螺栓连接箱形柱的滞回性能、承载力、刚度退化、延性以及耗能能力等受力特性。结果表明：整体式箱形截面柱和剪力键式全螺栓连接箱形截面柱均发生塑性铰破坏;滞回曲线饱满,具有良好耗能能力;剪力键和水平单向螺栓的设置可使全螺栓连接箱形截面柱承载力提高24.64%,竖向高强螺栓拉力降低29.44%;节点处钢连接件的设置约束了箱形截面柱的屈曲变形,与整体式箱形截面柱相比,全螺栓连接箱形截面柱的位移延性系数提高了26.47%;钢连接件间无滑移,剪力键式全螺栓连接节点连接可靠。通过剪力键式全螺栓连接节点与刚接节点有限元分析结果对比,表明在工程应用中箱形截面柱剪力键式全螺栓连接节点可等效刚接。采用GB 50011—2010《建筑抗震设计规范》对箱形截面柱剪力键式全螺栓连接节点进行承载力验算,计算结果与试验结果吻合。     

Experimental investigation of phase equilibrium in the Al–Nb–Hf ternary system at 600 °C and 400 °C

The phase equilibria in the Al–Nb–Hf ternary system at 600 °C and 400 °C were experimentally investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and electron probe microanalysis (EPMA/WDS). In each isothermal sections, 13 three-phase regions were measured. And their phase region boundaries were precisely determined. Among the actually measured binary compounds, only Al₃Nb, AlNb₂ and AlNb₃ have a large range of solid solubility. In addition, two stable ternary compounds τ1-Al₁₁Nb₄Hf₅ and τ2-Al₂NbHf₂, which had certain solid solubility, were newly discovered. On the basis of the experimental results and reasonable inference, the isothermal sections of ternary system at 600 °C and 400 °C were constructed.     

采用呋喃树脂自硬砂生产大断面球铁件

结合树脂砂生产的特点，严格控制化学成分，采用合适的球化剂和孕育剂，提高砂型紧实度，放置冷铁和控制冷铁使用次数，浇注前对型腔吹热风，加大浇注系统面积和气眼面积，保证液态补缩等，保证大断面球铁件质量。     

凸缘断面型钢多工位在线尺寸测量

研制了一种凸缘断面型钢的多工位轧件尺寸在线测量系统 ,测量精度可达 0 .0 1mm。该系统用于型钢轧制的闭环尺寸控制 ,借助于带人工智能的控制软件 ,可以明显提高型钢轧制的尺寸精度。用于轧制 H2 0 0mm× 10 0 mm铅质模拟轧件时 ,轧件的腰部厚度尺寸偏差可以从标准要求的± 1.0 mm提高至± 0 .1mm之内。用于 60 kg/m重轨的冷定径精轧 ,轨高的尺寸偏差可从± 0 .5 mm提高至± 0 .1mm     

陶瓷窑炉动态温度场测试及操作的优化

利用先进的红外热成像测试技术及自动设计的断面温差测试系统,进行了陶瓷窑炉火焰温度场分布的测试,窑墙表面温度场的测试、干燥器干燥效果的测试及窑内同一横断温差分布的测试。研究了影响火焰温度场的各因素,为窑炉的控制及操作的优化提供了可靠的依据。     

NURBS曲面RCS的物理光学法混合计算

基于近似驻相法和直接积分法,在利用物理光学法(PO)计算NURBS曲面的雷达散射截面(RCS)的问题中提出一种混合积分法.这种方法既保持积分精度,又提高了计算速度.此外,归纳了七种不适合用一般驻相法处理的剖分面元.同时验证了计算中采用NURBS面元剖分对于提高目标RCS计算精度的作用.