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In this study, TiB2 cermet and TiAl-based alloy are vacuum brazed successfully by using Ag-Cu-Ti filler metal.The microstructural analyses indicate that two reaction products, Ti ( Cu, Al ) 2 and Ag bused solid solution ( Ag ( s. s ) ) , are present in the brazing seam, and the iuterface structure of the brazed joint is TiB2/TiB2 Ag ( s. s ) /Ag ( s. s ) Ti ( Cu,Al)2/Ti( Cu, Al)2/TiAl. The experimental results show that the shear strength of the brazed TiB2/TiAl joints decreases us thebrazing time increases at a definite brazing temperature. When the joint is brazed at 1 223 K for 5 min, a joint strength up to 173 MPa is achieved. 相似文献
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Friction stir welding of AZ31 magnesium alloy 总被引:3,自引:0,他引:3
Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy ( SEM ) , micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious. 相似文献
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The analysis of the microstructural characterization and phase composition of electron beam welded joint zones of Ti- 43Al-9V-O. 3Y alloy has been done in this study. The welded seam is mainly composed of B2 phase, the partial γ + α2 twophase lamellar structure and granular γm phase. And the lanthanon Y existed as YAl2 phase and served as grain refined. The impact of different cooling rates on joint microstructure, fracture characteristic and tensile strength were investigated. The high cooling rate restrained the structural transformation and resulted in the ordering structure. The fracture of the joint was brittle cleavage fracture because the ordering structure went against restraining the crack propagation. With the decrease of cooling rate, the transformation amounts of lamellar structure increased, and the fracture presented the layered and crosslayered characteristic. 相似文献
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Effect of welding current on strength and microstructure in resistance spot welding of AZ31 Mg alloy
In this paper, resistance spot welding were performed on lmm-thickness magnesium AZ31B plates. The effect of welding current on the microstructure and tensile shear force was investigated. It was found that the welding current governed the nugget growth, and the nugget could not form if current levels were insufficient. The nugget revealed a homogeneous, equiaxed, fine-grained structure, which consisted of non-equilibrium microstructure of α-phase dendrites surrounded by eutectic mixtures of α and β( Mg17All2 ) in the grain boundaries. With increasing welding current, the size of grains in nugget would be more smaller and uniform, and the width of plastic rings would be larger. Tensile shear tests showed that tensile shear force of the joints increased with increasing welding current when the welding current was smaller than 17 000 A. The maximum tensile shear force was up to 1980 N. 相似文献
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TiAl/40Cr钢扩散连接界面组织结构对接头强度的影响 总被引:1,自引:0,他引:1
扩散连接界面组织结构是影响连接性能的关键因素,不同的界面组织结构及生成相所决定的接合强度不同.本文研究了TiAl/40Cr钢的扩散连接,结果显示:连接温度过高及连接时间过长时,由于界面处形成了过多的TiC脆性层及Ti3Al FeAl FeAl2的金属间化合物混合层,接头拉伸强度低;当连接温度较低及连接时间较短时,界面紧密接触与元素扩散不充分,接头拉伸强度也较低.脆性TiC层的生成导致TiAl与40Cr钢之间的扩散连接性能较差,接头均破断于TiC层或TiC层与Ti3Al FeAl FeAl2的金属间化合物混合层之间. 相似文献
10.
基于电子束焊接过程的传热与受力物理过程分析,建立相应模型,对电子束定点焊接304不锈钢的温度场与流场进行数值模拟,研究电子束焊接熔池流动行为及焊缝成形规律.结果表明,电子束加热阶段,熔池上表面温度梯度达到106 K/m,熔池表面峰值温度高,在沸点温度附近波动,强烈的金属蒸汽反作用力成为熔池流动的主要作用力,促使熔池中心下凹并不断波动,熔池冷却凝固阶段,金属蒸汽反作用力下降,熔池金属表面张力梯度引起的Marangoni对流成为熔池金属流动主要驱动力,促使焊缝表面熔宽增大,熔池凝固后焊缝上表面宽度为1.9 mm,中心处宽度为1.6 mm,下表面宽度为1.8 mm. 相似文献