SiC_p/2024与2219铝合金电子束焊接

分别采用电子束对中焊、偏束焊技术,研究了Si C颗粒增强铝基复合材料Si Cp/2024与2219铝合金的接头组织及力学性能.结果表明,对中焊时接头易出现Si C增强相的偏聚,同时发生严重的界面反应,生成大量脆性相Al4C3,接头抗拉强度最高为104 MPa.采用偏束焊工艺可以很好地抑制界面反应,通常只在焊缝上部与Si Cp/Al热影响区上部生成少量脆性相Al4C3,接头抗拉强度最高可达131 MPa.试件均断裂在母材界面反应层上,且为明显的脆性断裂.不同工艺下接头横截面硬度分布存在突变区,该区域在Si Cp/2024熔合区附近,该处脆性相Al4C3的生成导致硬度升高.     

SiCp/Al复合材料电子束焊接接头组织及性能

对SiCp/Al复合材料自身进行电子束焊接,研究了其接头成形、焊缝组织、热影响区组织及接头力学性能.结果表明,SiCp/Al复合材料自身直接电子束焊接时,接头的主要缺陷是焊缝成形差、易形成两侧堆积颗粒物的凹槽;焊缝组织中存在界面反应产生的灰白色初生硅、深灰色针状相Al4C3以及Al-Si共晶中的浅灰色针状共晶硅,形成脆性区,拉伸断裂位置便在此处,断裂为脆性断裂.熔合区附近硬度较高,与焊缝区组织及硬度差异较大.接头的最高强度为73 MPa,仅占母材平均抗拉强度的41％.     

Influence of In Situ Reaction on the Microstructure of SiC<Subscript>p</Subscript>/AlSi7Mg Welded by Nd:YAG Laser with Ti Filler

The effect of in situ reaction on the microstructure of Nd:YAG laser welded joints of aluminum matrix composite SiC_p/AlSi7Mg was studied. Results showed that the laser welding with Ti filler improved the tensile strength of welded joints. Moreover, the laser welding with in situ reaction effectively restrained the pernicious Al₄C₃ forming reaction in the interface between aluminum matrix and reinforcement particles. Simultaneously, the reaction-formed TiC phase distributed uniformly in the weld. This permitted SiC_p/AlSi7Mg composite to be successfully welded by Nd:YAG laser.     

异种搅拌摩擦焊制备铜铝合金双金属纳米复合材料

对纯铜与AA5754合金进行对接搅拌摩擦焊接.为了降低金属间化合物的有害影响,在搅拌摩擦焊(FSW)接头中添加纳米SiC强化颗粒.采用拉伸试验、显微硬度试验、扫描电镜和X射线衍射分析方法研究焊接接头的性能.结果显示,当焊接速度为50 mm/min、转速为1000 r/min时接头的性能最好.纳米SiC颗粒的存在使搅拌区...     

Ti-Ni合金对SiCp/AlMMCs等离子弧原位焊接焊缝性能的影响

以Ti-Ni合金作为填加材料,采用氮氩混合等离子气对SiCp／Al基复合材料进行等离子弧原位焊接。结果表明,填加Ti-Ni合金进行等离子弧原位焊接,在焊缝组织中生成了新的增强颗粒TiN,TiC,A1N,Al3Ti和Al3Ni,未发现明显的针状相生成,有效的抑制了脆性相Al4G3并且接头组织致密,结合较好。Ni元素的添加,降低了SiC溶解程度,使得熔池中的结晶热显著提高,改善了熔池的流动性。同时在焊缝组织中形成了新的增强相AlNi,Al3Ni,从而有效地提高接头的力学性能。采用Ti-Ni合金进行等离子弧原位焊接,接头的抗拉强度为215．4MPa,达到母材强度的67．3％。     

Formation of intermetallic compounds in Al and Mg alloy interface during friction stir spot welding

The spot welding of Al plate to Mg plate was produced by friction stir spot welding using various tool rotation speed and duration time of the tool to investigate the effects of the welding parameters on the reaction of Al and Mg alloy. The interface microstructure and phase were investigated using optical microscopy, scanning electron microscopy and X-ray diffraction. The mechanical properties of the joints are evaluated using tensile test. Experimental results show that intermetallic compounds were formed in the interface of the Al and Mg alloys. The thickness of intermetallic compounds layer increases with increasing tool rotation speed and duration time, and has a significant effect on the strengths of the joints. Heavy thickness of intermetallic compounds layer seriously deteriorates the mechanical properties of the joints. The intermetallic compounds layer mainly contains Al₃Mg₂ and Al₁₂Mg₁₇     

Si,Mg对铝/钢熔钎焊焊接接头力学性能的影响

采用脉冲旁路耦合电弧MIG熔钎焊方法,分别采用4043,5356铝合金焊丝对5052铝合金/镀锌钢异种金属进行了搭接焊.通过扫描电镜（SEM）,能谱仪（EDS）,X射线衍射仪（XRD）对铝/钢连接界面、接头断裂行为及断口形貌进行了分析,发现5356铝合金焊丝焊接接头的润湿角要大于4043铝合金焊丝焊接接头的润湿角,合金元素Si既可改变界面反应层金属间化合物的形态同时还可显著减少Fe₂Al₅层的厚度.拉伸试验发现5356铝合金焊丝焊接所得接头主要断裂于界面反应层,属于脆性断裂;4043铝合金焊丝焊接所得接头主要断裂于熔合区,是以韧性断裂为主的混合断裂.通过对4043铝合金焊丝焊接所得接头进行显微硬度测试,发现热影响区组织的显微硬度明显低于其它区域的显微硬度,这导致4043铝合金焊丝焊接接头主要断裂于熔合区.     

Influence of pulse impact on properties of liquid phase pulse impact diffusion welding SiCp/AlSi7Mg and its welding mechanism

Abstract

The influence of pulse impact on the microstructure and properties of welded joints of aluminium matrix composite SiC_p/AlSi7Mg by liquid phase pulse impact diffusion welding (LPPIDW) and its welding mechanism had been studied. It showed that during LPPIDW, under the effect of pulse impact, the interface state between SiC particle and matrix was prominent, the initial pernicious contact state of reinforcement particles had been changed from reinforcement (SiC)/reinforcement (SiC) to reinforcement (SiC)/matrix/reinforcement (SiC), and the harmful microstructure or brittle phase was restrained from the welded joint. Moreover, the density of dislocation in the matrix neighbouring to and away from the interface was higher than that of its parent composite and the dislocation entwisted each other intensively. Furthermore, the deformation mainly occurred in the matrix grain and the matrices around SiC particles engendering intensive aberration offered a high density nucleus area for matrix crystal in favour of forming nanograins, which improved the properties of welded joints distinctly, resulting in welding the composite successfully. Consequently, the tensile strength of the welded joints was up to 179 MPa, which was ～74˙6% of the strength of SiC_p/AlSi7Mg (as stir cast), and its corresponding radial deformation was less than 3%, suitable for the demand of deformation of welded specimens.     

Microstructural and mechanical properties of friction stir welded aluminum/copper lap joints

This paper focuses on the microstructural and mechanical properties of the friction stir welding (FSW) of 1060 aluminum alloy to a commercially pure copper. A number of FSW experiments were carried out to obtain the optimum mechanical properties by adjusting the rotational speed and welding speed in the range of 750–1500 rpm and 30–375 mm/min, respectively. Various microstructures with different morphologies and properties were observed in the stir zone. The results indicated that Al₄Cu₉, AlCu and Al₂Cu are the main intermetallic compounds formed in the interfacial region. The effect of formation of hard and brittle intermetallic phase at the interface of the joints on the shear strength of the joint is discussed.     

铜/钛合金电子束焊接工艺优化

研究了QCr0.8/TC4电子束焊接工艺及接头组织,由于铜合金热导率高而熔化量较小,以及焊缝中生成大量脆性金属间化合物相,因此对中焊时接头强度较低.采用偏铜侧进行非对中电子束焊接,接头抗拉强度随偏束量的增大而增高,偏束量为0.8mm时接头最高抗拉强度为270.5MPa.断裂发生在TC4侧熔合线处,为脆性准解理断裂特征.偏铜焊时接头成形得到改善,焊缝包括熔合区及TC4侧反应层两部分.熔合区主要由铜基固溶体组成,硬度较TC4母材有所降低.反应层成分过渡较大,含有多种金属间化合物相.随着工艺参数的变化,反应层厚度也发生变化,从而对接头性能产生影响.     

SiCp/Al复合材料与Fe36Ni合金超声波钎焊

利用超声波钎焊方法使用ZnAlSi钎料实现了Fe36Ni合金与45%SiC_p/2024Al和55%SiC_p/A356两种复合材料的连接,并得到由SiC颗粒增强的复合焊缝.通过扫描电镜、能谱等方法对焊缝的微观结构以及断口形貌进行了观察,对接头的压剪强度进行了测试,分析了Fe36Ni与两种复合材料钎焊接头微观组织和接头强度的差异.结果表明,在Fe36Ni与两种复合材料的钎缝中,钎料与两侧母材界面均形成良好的冶金结合,SiC颗粒均匀分布于焊缝中.Fe36Ni与45%SiC_p/2024Al的接头抗剪强度为110~145 MPa,Fe36Ni与55%SiC_p/A356的接头抗剪强度为75~85 MPa.Fe36Ni与45%SiC_p/2024Al的接头断裂位置为钎缝中,而Fe36Ni与55%SiC_p/A356的接头断裂位置位于Fe36Ni与钎料的界面上.     

Tensile resistance,microstructures of intermetallic compounds,and fracture modes of welded steel/aluminum joints produced using laser lap welding

The joining of DP780 steel to Al5052 was conducted by laser lap welding, in which the metal vapor and spatters were monitored by a high-speed camera. A universal testing machine was used to test the mechanical properties of the welded joints, and the changing law of lap tensile resistance with the laser welding parameters was analyzed. Optical microscope and scanning electron microscope were used to observe the macro-structure and micro-structure, respectively. Three different intermetallic compounds (IMCs) phases, i.e. banded Fe₂Al₅, FeAl₂ and needle-like FeAl₃ were generated at the steel/Al interface on microscopic observation. The aim of this research is to investigate the relationship among the lap tensile resistance, the welding parameters and the failure mode under different energy densities. Experimental results showed that the steel/Al joints have two different fracture modes at low heat input and high heat input. The failures happened along the heat-affected zone of the weld and along the steel/Al joint interface, respectively. And both of the two failure modes are brittle fractures. Additionally, cracks appeared at the fracture interface, and needle-like particle clusters were found in the fracture microstructure.     

Mechanical properties of laser-pressure-welded joint between dissimilar galvannealed steel and pure aluminium

Dissimilar metal joints of Zn-coated Galvannealed steel (GA steel) and commercially available pure aluminium (A1050) sheets were produced by changing the laser power and the roller pressure by the laser pressure welding method. By this method, the YAG laser beam was irradiated into a flare groove made by these dissimilar metal sheets. In addition, the laser beam was scanned at various frequencies and patterns through the fθ lens using two-dimensional scanning mirrors. Then the sheets were pressed by the pressure rolls to be joined.

The compound layers in the weld interface were observed by an optical microscope and the layer thicknesses were measured. The thicknesses ranged from 7 to 20 μm. The mechanical properties of the welded joints were evaluated by the tensile-shear test and peel test. In the tensile-shear test, the strengths of the joints produced under the most welding conditions were so high that the fracture occurred through the base aluminium sheet. In the peel test of the specimens subjected to a laser beam of 1200–1400 W power under roller pressure of 2.94 kN, the specimen fracture took place in the base aluminium sheet. Even if the compound layer was thick, high joint strength was obtained. On the other hand, the specimen fractured in the weld interface at a laser power of 1500 W. The results of X-ray diffraction on the peel test specimen surface identified that the intermetallic compound on the GA steel side was Fe₂Al₅Zn_0.4. Moreover, the aluminium parts adhering to the GA steel side were confirmed. These results suggest that the fracture in the peel test occurred between the compound layer and A1050 and partly in the base aluminium. A micro-Vickers hardness test was performed to examine the hardness distribution in the compound layer. The hardness values near A1050 and GA steel were about 100 and 470 Hv, respectively, which suggests that the compound layer should not necessarily consist of brittle intermetallic compounds. It is therefore concluded that laser pressure welding could produce high strength joints of GA steel and A1050 dissimilar materials.     

Intermetallic compounds in friction stirred lap joints between AA5754/galvanised ultra-high strength steel

This paper presents results of joining of AA5754 and DP800 based on the friction stir welding process. Joints were produced by the tool made of H13 tool steel which was allowed to penetrate through the aluminium sheet until reaching the surface of steel sheet without penetrating into it. This approach is an economic and robust way to operate the dissimilar welding process without excessive tool cost. Bonding was achieved by interfacial diffusion reactions between aluminium and iron with a formation of intermetallic compounds. The formation of brittle intermetallic compounds at the interface between the materials was studied. Three intermetallic phases were found at the interface including Al₁₃Fe₄, Al₅Fe₂ and Fe₃Zn₁₀. A range of process parameters was identified with a thickness of the intermetallic layers around 2?µm. Shear fracture failure mode was observed under overlap loading. The mechanisms of formation of the joints and factors controlling the strength were discussed.     

Influence of tool pin design on properties of dissimilar copper to aluminum friction stir welding

Dissimilar friction stir welding (FSW) of copper and aluminum was investigated by nine different tool designs, while the rest of the process parameters were kept constant. Mechanical and metallurgical tests such as macrostructure, microstructure, tensile test, hardness, scanning electron microscope and electron X-ray spectrographs were performed to assess the properties of dissimilar joints. The results exhibited that, the maximum joint strength was achieved by the tool of cylindrical pin profile having 8 mm pin diameter. Besides, the fragmental defects increased as the number of polygonal edges decreased, hence the polygonal pin profiles were unsuitable for dissimilar FSW butt joints. Furthermore, the tensile strength increased as the number of polygonal edges increased. Stir zone of polygonal pin profiles was hard and brittle relative to cylindrical tool pin profiles for same shoulder surface. Maximum hardness of HV 283 was obtained at weld made by the polygonal square pin profile. The hard and brittle intermetallic compounds (IMCs) were prominently presented in the stir zone. Phases of IMCs such as CuAl, CuAl₂, Cu₃Al and Cu₉Al₄ were presented in the stir zone of dissimilar Cu–Al joints.     

Effect of Intermetallic Compound Phases on the Mechanical Properties of the Dissimilar Al/Cu Friction Stir Welded Joints

Types and distribution of intermetallic compound phases and their effects on the mechanical properties of dissimilar Al/Cu friction stir welded joints were investigated. Three different rotation speeds of 1000, 1200 and 1400 rpm were used with two welding speeds of 20 and 50 mm/min. The results show that the microstructures inside the stir zone were greatly affected by the rotation speed. Complex layered structures that containing intermetallic compound phases such as CuAl₂, Al₄Cu₉ were formed in the stir zone. Their amount found to be increased with increasing rotation speed. However, the increasing of the rotation speed slightly lowered the hardness of the stir zone. Many sharp hardness peaks in the stir zones were found as a result of the intermetallic compounds formed, and the highest peaks of 420 Hv were observed at a rotation speed of 1400 rpm. The joints ultimate tensile strength reached a maximum value of 105 MPa at the rotation speed of 1200 rpm and travel speed of 20 mm/min with the joint efficiency ranged between 88 and 96% of the aluminum base metal. At the travel speed of 50 mm/min, the maximum value of the ultimate tensile strength was 96 MPa at rotation speed of 1400 rpm with the joint efficiency ranged between 79 and 90%. The fracture surfaces of tensile test specimens showed no evidence for the effect of the brittle intermetallic compounds in the stir zones on the tensile strength of the joints.     

钢侧偏束电子束焊接纯铝/Q235异种金属接头试验

采用钢侧偏束电子束焊接方法对铝/钢异种金属接头进行了连接,对接头组织和相组成进行了分析,并对接头抗拉强度进行了了测试.结果表明,钢侧结合良好,焊缝组织均匀,铝侧熔合区存在过渡层,其内有金属间化合物层存在.适当的钢侧偏束量能够提高接头强度,在文中试验范围内,在偏束量为0.5 mm时获得了相对最高的抗拉强度69 MPa.金属间化合层的存在弱化了接头强度,断裂呈脆性特征.     

Preparation and characterization of SiCp/2024Al composite foams by powder metallurgy

SiC_p/2024Al composite foams were manufactured by powder metallurgical methods using foaming agent CaCO₃ in order to enrich the foam fabrication process and promote its development and extensive application. The effects of CaCO₃ and SiC volume fractions on the foaming behaviours were investigated by means of SEM and Magiscan-2A image analysis technique. The influence of SiC content on the compressive behaviour was analyzed using Gleeble 1500 thermal simulation testing machine. The experimental results show that with increasing the foaming agent, the porosity and pore dimension increase first and decrease later. With increasing the reinforcement content, the porosity and pore dimension decrease. The compressive curves reveal that the introduction of SiC particles can improve compressive yield strength and energy absorption capacity. Meanwhile, it is found that SiC_p/2024Al composite foams are the brittle foam materials.     

冷金属过渡搭接焊镁铝异种金属接头组织及性能

采用冷金属过渡（CMT）焊接工艺,以HS201铜焊丝作为焊缝填充金属对AZ3l镁合金和6061铝合金进行搭接焊接．测试了接头的抗剪强度和显微硬度,并利用光学显微镜（OM）、扫描电镜（SEM）、能谱（EDS）对接头的组织成分及断口形貌进行了分析．结果表明,当焊接电流为109A,电弧电压10．9V,送丝速度4．9mm／s,...     

钎料形态对半固态加压反应钎焊接头的影响

采用自制不同形态的Al-Si-Mg-Cu-Ti钎料对70% SiC_p/Al复合材料进行了半固态加压反应钎焊,阐述了该焊接方法的内涵,分析了接头组织性能. 结果表明,填充粉末钎料时,钎缝组织为铝合金基体、深灰色环状和块状Ti₇Al₅Si₁₂和块状Ti;填充片状钎料时,钎缝组织为铝合金基体和短棒状Ti₇Al₅Si₁₂. 接头界面结合情况是影响接头性能的主要因素. 填充粉末钎料时,钎料与母材结合充分,原子扩散通道多,接头界面结合好,没有明显分界线,接头力学性能好,抗剪强度达92.1 MPa,断口属于韧脆混合断口;填充片状钎料时,界面处有明显分界线,接头力学性能差,抗剪强度为43.9 MPa,断口为脆性断口.