共查询到17条相似文献,搜索用时 78 毫秒
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采用电阻点焊技术焊接TA2纯钛板和AZ31B镁合金板。研究了不同焊接参数(点焊电流、点焊时间和电极压力)对焊点拉剪强度的影响,分析Ti/Mg焊点界面区域微观组织构成及显微硬度分布。分析结果表明,Ti/Mg焊点拉剪强度随点焊电流、焊接时间和电极压力的增大呈现先增加后降低的趋势。当采用点焊电流10 kA,焊接时间8周波,电极压力4 kN等参数时,Ti/Mg焊点拉剪力达到最大值3.7 kN。能谱分析表明,Mg/Ti界面反应层由Mg 17 Al 12 ,α-Mg和TiAl 3 等相组成,其具有最大显微硬度146 HV。 相似文献
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采用体视显微镜、激光共聚焦扫描显微镜(CLSM)和扫描电镜(SEM)等设备研究了镁合金电阻点焊接头的断裂模式和断口形貌。结果表明,在拉剪试验中,接头断裂模式主要有两种,即结合面断裂和纽扣断裂。熔核内的结晶裂纹对结合面断裂接头性能影响较大,而对纽扣断裂接头性能影响不大。对于纽扣断裂,裂纹在熔核的胞状树枝晶区萌生,而后沿着熔核周围的胞状树枝晶区迅速扩展,并沿板厚方向依次通过热影响区和母材。结合面断裂断口表面具有金属光泽,且较为平整。而纽扣断裂断口形貌在不同位置上具有不同的特点,这些特点与不同位置所受的应力状态有关。 相似文献
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镁合金电阻点焊液化裂纹机理研究 总被引:1,自引:0,他引:1
为了获得高性能的镁合金电阻点焊接头,利用体视显微镜、扫面电镜等设备研究了点焊接头热影响区裂纹的形貌,并研究了裂纹的形成机理及控制方法.结果表明,热影响区裂纹属于液化裂纹,其出现在紧靠点焊熔核的热影响区,并且能够扩展到点焊接头的表面,它可能是由结晶裂纹在熔核边缘产生的应力集中引起的.液化裂纹的形成主要与低熔点液化膜(由低固溶度的原子扩散到熔化的晶界而形成)和冷却过程中产生的拉伸应力有关.应该选择相对低的热输入(即相对小的焊接电流、短的焊接时间或者高的电极压力)来降低热影响区液化裂纹敏感性. 相似文献
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采用电阻点焊工艺对厚度为2 mm的5182铝合金和5754铝合金进行搭接焊,并使用金相显微镜观察其显微组织特点,使用拉伸试验机和维氏显微硬度仪测试焊接接头的力学性能。结果表明,焊接接头由3个典型区域组成:母材区、热影响区和熔核区;熔核区主要由边缘柱状晶和中心等轴晶组成,中心等轴晶区体积约占整个熔核区的90%。5182铝合金侧的热影响区出现较多大颗粒析出物,并出现液化裂纹,5754铝合金侧的热影响区无明显的析出物与液化裂纹产生。焊接接头的断裂形式为纽扣型断裂,均为 5754铝合金侧的熔核被剥离。熔核中柱状晶区硬度高于等轴晶区,位于两种铝合金侧的热影响区硬度均高于其对应的母材硬度。 相似文献
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By means of the quadratic regression combination design process, the regression equations of nugget diameter and tensile shear load of spot welded joint were established. Effects of welding parameters on the nugget diameter and the tensile shear load were investigated. The results show that effect of welding current on nugget diameter is the most evident. And higher welding current will result in bigger nugget diameter. Besides, interaction effect of electrode force and welding current on tensile shear load is the most evident compared with others. The optimum welding parameters corresponding to the maximum of tensile shear load have been obtained by programming using Matlab software, which is 4, 7 kN electrode force, 28 kA welding current and 4 cycle welding time. Under the condition of the optimum welding parameters, the joint having no visible defects can be obtained, nugget diameter and tensile shear load being 6. 8 mm and 3 256 N, respectively. 相似文献
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在电阻点焊过程中喷溅的产生直接降低焊接接头的强度,因此是最不希望出现的焊接缺陷.文中引入基于显微接触理论的接触电阻模型,通过轴对称有限元模型分析了镁合金电阻点焊过程中的温度场分布及塑性变形过程,以揭示内部喷溅产生的原因.结果表明,由于AZ31镁合金高热导率、低熔点、低比热容和大的线膨胀系数,焊接中需要采用大电流短时间的强参数焊接,所以相对于铝合金和钢铁来说,喷溅在镁合金焊接中更容易发生.内部喷溅产生的原因主要与金属熔化导致熔核内部压强增大相关,增加的压力致使周围的塑性环产生缺口,保护液态金属冲破周围固态金属的束缚,形成喷溅. 相似文献
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对AZ31镁合金与6061铝合金进行了电阻点焊,利用金相显微镜、扫描电子显微镜(SEM)、能谱分析(EDS)、X射线衍射分析(XRD)研究了点焊接头的组织及力学性能。结果表明:AZ31镁合金与6061铝合金异种金属点焊接头冶金结合良好,焊接界面清晰,无明显缝隙。熔合区组织由边缘柱状晶区和中心树枝晶组成,主要含有镁和铝两种元素,且镁元素含量远高于铝元素。接头镁侧断面由大量α-Mg和少量β-Mg17Al12组成,呈混合型断裂特征;铝侧断口由Mg、Al和β-Mg17Al12组成,呈解理断裂。随焊接电流增大,点焊接头最大剪切应力增加。 相似文献
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Optimization of parameters and study of joint microstructure of resistance spot welding of magnesium alloy 总被引:1,自引:0,他引:1
Experimental investigations on the DC spot welding of Mg alloy AZ31B are presented. Experiments are carried out to study the influence of spot welding parameters ( electrode force, welding heat input and welding time) on the tensile shear load and the diameter of nugget, based on an orthogonal test and analysis method. The optimum parameters are as follows: electrode force is 2 000 N, welding heat input is 80% and welding time is 6 cycles. The microstrueture of spot weld is single fine equiaxed crystals in the nugget, of which the structure is β-Mg17Al12 precipitated on α-Mg boundaries induced by nonequilibrium freezing. And the surface condition of the workpiece has great influence on the joint quality. 相似文献
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Resistance spot welded magnesium alloy joints can fail in two markedly different failure modes(interfacial failure and button pullout failure)under tensile shear loading conditions.For button pullout failure,the crack first propagates along cellular dendritic structure of the nugget circumference,and then passes through heat-affected zone(HAZ)and base metal in sequence.The tensile shear load has smaller values under the interracial failure occurring in a small weld nugget as compared to the button pullout failure appearing in a large weld nugget.The tensile shear load increases with the increasing nugget diameter for expulsion free joints.However,for joints which experienced expulsion,the tensile shear load decreases in spite of nugget diameter increasing.Under the equivalent nugget diameter(5.8 mm),the tensile shear load of joints with 9 × 10-4 g KBF4 addition was increased by around 20% as compared to that of joints without KBF4 addition. 相似文献
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针对2.0 mm厚的AZ31B镁合金以及1.0 mm厚的SPHC镀锌钢板,采用kDWJ-17型三相次级整流电阻焊机进行焊接试验,通过对接头的金相观察、扫描电镜分析,结合原子结合能研究点焊接头拉剪断裂特征.结果表明,点焊接头断裂的形式呈现结合面断裂和纽扣断裂两种方式,纽扣断裂抗拉剪力学性能优于结合面断裂,纽扣断裂断口是以韧性断口为主,脆性断裂为辅的混合断口.熔核区以Fe-Al化合物为主时发生纽扣断裂,熔合线边缘晶粒尺寸粗大以及熔核区Fe-Al化合物结合能大,使其断裂位置在熔合线边缘.熔核区以Mg-Zn化合物为主时发生结合面断裂,其Mg-Zn化合物结合能偏小,容易被拉断. 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