Al-12.7Si-0.7Mg合金脉冲MIG焊接头组织与性能

采用进口ER4047作为填充焊丝对Al - 12.7Si -0.7Mg合金热挤压板材实施脉冲MIG直缝对焊.利用金相观察、显微硬度测定及拉伸性能测试等方法研究了焊接接头的显微组织与力学性能.结果表明:利用优化的焊接工艺参数,获得了外观和内部质量良好的焊缝,焊接接头平均抗拉强度为180 MPa,达到基材的98％.     

Sintering parameters and mechanical properties of injection moulded aluminium powder

Abstract

This paper describes the microstructural and mechanical properties of injection moulded aluminium powder. Gas atomised aluminium powder was injection moulded with wax based binder. The critical powder loading for injection moulding was 62·5 vol.-% for feedstock. Binder debinding was performed in solvent and thermal method. After debinding, the samples were sintered at different temperatures and times in high purity N₂. Metallographic studies were conducted to determine the extent of densification and the corresponding microstructural changes. The results show that gas atomised aluminium powder could be sintered to a maximum 96·2% of theoretical density. Maximum density, tensile strength and hardness were obtained when sintered at 650°C for 60 min.     

焊接速度对机器人搅拌摩擦焊AA7B04铝合金接头组织和力学性能的影响

针对熔化焊在焊接AA7B04铝合金时易在焊缝中出现孔洞等缺陷,且接头性能下降明显、焊后变形大,以及采用铆接等机械连接方式会增加连接件的重量等问题,采用集成了搅拌摩擦焊末端执行器的KUKA Titan机器人对2 mm厚AA7B04高强铝合金进行了焊接,在转速为800 r·min^-1的条件下,研究了焊度对焊接过程中搅拌头3个方向的受力F_x、F_y和F_z的影响.研究发现,F_z受焊速的影响显著,随焊速的增加而降低.利用光学显微镜、透射电子显微镜、拉伸试验、三点弯曲试验和硬度测试等方法,研究了不同焊速下AA7B04铝合金接头的微观组织和力学性能.结果表明：当焊速为100 mm·min^-1时,接头的抗拉强度最高为447 MPa,可达母材的80%,且所有接头的正弯和背弯180°均无裂纹;接头横截面的硬度分布呈W型,硬度最低点出现在热力影响区和焊核区的交界处,焊速不同会导致不同的焊接热循环,且随着焊速的增加接头的硬度随之增加;焊核区组织发生了动态再结晶,生成了细小的等轴晶粒,前进侧和后退侧热力影响区的晶粒均发生了明显的变形;前进侧热影响区析出η'相,后退侧热影响区因温度较高析出η'相和尺寸较大的η相.     

Nugget formation and growth during resistance spot welding of aluminium alloy 5182

Abstract

Surface interaction at the worksheet/worksheet interface during resistance spot welding of aluminium alloy 5182 with spherical tip electrodes was investigated. Oxide layer cracking and nugget formation were focused. Both experimental work and finite element analysis were employed to explain the contact behaviour at this interface. It was found that sheet separation and thus bending occurred during the squeezing phase of the resistance spot welding process and suggested a profound influence on nugget formation. The sheet separation caused enlarged and aligned cracks in the surface oxide layers which led to a good metal‐to‐metal contact near the periphery of the faying surface. High current densities which occurred at the beginning of the current phase caused significant heat generation in this zone. Consequently, the melting at the faying surface started near the periphery and moved in towards the central zone of the contact region to produce a ‘doughnut shaped’ nugget with a filled‐in but thin central region.

On a étudié l'interaction de la surface à l'interface feuille de travail‐feuille de travail lors du soudage par points par résistance de l'alliage d'aluminium 5182 avec des électrodes à bout sphérique. On s'est concentré sur la fracture de la couche d'oxyde et sur la formation du noyau. On a utilisé tant le travail expérimental que l'analyse par éléments finis pour expliquer le comportement de contact à cette interface. On a trouvé que la séparation de la feuille, et donc le pliage, se produisait lors de la phase de compression du procédé de soudage par points par résistance, suggérant une influence profonde sur la formation du noyau. La séparation de la feuille résultait en fissures agrandies et alignées dans les couches d'oxyde de la surface, ce qui amenait un bon contact de métal à métal près de la périphérie de l'aire de contact. Des densités élevées de courant, qui se produisaient au début de la phase de courant, résultaient en un dégagement important de chaleur dans cette zone. Conséquemment, la fonte de l'aire de contact commençait près de la périphérie et se déplaçait vers la zone centrale de la région de contact, produisant un noyau en forme d'anneau avec une région centrale remplie, mais mince.     

Improving the mechanical properties of 2024 Al alloy by cryo rolling

Ultra fine grained (1 micron size) materials usually exhibit more strength. Most of the approaches to refine microstructure lead to decrease in ductility. Cryo rolling is a successful technique; samples are rolled at cryogenic temperature, to improve strength of an age hardenable alloy with minimum loss in ductility. Aging after cryo rolling ensures good strength and ductility due to bimodal structure and nano sized precipitation of S’ phase. Al 2024 alloy are partially solutionised to retain some T-phase particles, which are very effective in accumulating dislocations during cryo-rolling, and in turn promoted the precipitation of Al₂CuMg precipitates with a size of 10–40 nm. The nano sized Al₂CuMg precipitates and bimodal grain structure leads to simultaneous increases in strength and ductility.     

Effect of bake hardening treatment on the mechanical behaviors of aluminum alloy spot welding joints

In this paper, the mechanical behaviors of the spot welding aluminum alloy in both baked and unbaked conditions are investigated. The spot welded specimens with two different base aluminum alloy sheets are studied by tensile and fatigue tests. The test results of unbaked specimens are compared with the baked which are baked at 185°C for 20 min. The stress distribution of the specimens and the fatigue life under different stress is simulated by finite element method (FEM). The paint bake treatment can increase the ductility of both base materials and spot joints. The fatigue life is increased with high loading stress due to the pinning effect; while with low fatigue load, it has the opposite rule because the compressive residual stress is released during the bake hardening process, which can restrain the fatigue crack growth rate in low stress. The simulated results of FEM model can well verify the experiment data.     

国产A6N01铝合金型材MIG焊接头的微观组织与力学性能

利用金相观察、显微硬度测定、拉伸和弯曲性能测试等方法研究了A6N01-T5铝合金型材MIG焊接接头的显微组织和力学性能.结果表明：焊接接头焊缝中心金属为明显的激冷形成的铸态组织,呈等轴晶状;熔合区靠近焊缝侧的结晶形态为沿散热方向排列的柱状晶,邻近熔合区的热影响区晶粒粗化.焊缝中心处具有较高的显微硬度,在距离焊缝中心10~12 mm处的热影响区显微硬度值最低.国产A6N01-T5铝合金型材焊接接头抗拉强度达到欧洲标准DIN EN 288-4的要求.     

Structure and mechanical properties of the welded joints of large-diameter pipes

The structure and mechanical properties of the technological welded joints of large-diameter pipes of strength class K60 produced by two companies are studied. Along with standard mechanical properties (σ_0.2, σ_u, δ, ψ), specific work of deformation a (tensile toughness) and true rupture strength S _f are estimated from an analysis of the stress-strain diagrams constructed in true coordinates. The mechanical behavior is found to be different for samples cut from different zones of a welded joint (central weld, heat-affected zone, and base metal). The mutual correlation between parameters a, S _f, and impact toughness KCV is considered.     

Effect of cerium on microstructure,mechanical properties and corrosion properties of Al-Zn-Mg alloy

The effects of trace Ce on the microstructure,mechanical properties and corrosion resistance of Al-Zn-Mg alloy were studied by means of metallographic analysis,scanning electron microscopy(SEM),mechanical tensile test,slow strain rate tensile test,cyclic polarization curve test,electrochemical impedance spectroscopy test and anodic oxidation test.The results show that the addition of trace Ce has little effect on the strength of Al-Zn-Mg alloy,but can significantly improve the corrosion resistance of the alloy;The mechanical properties and corrosion resistance of the alloys decrease significantly with the addition of excessive Ce;the addition of 0.04 wt%Ce can reduce significantly the self-corrosive current density of AlZn-Mg alloy and increase obviously passivation film resistance of the alloy.The stress corrosion sensitivity index decreases from 0.612 to 0.219,which improves the corrosion resistance properties significantly.     

Influence of extrusion ratio and temperature on microstructure and mechanical properties of 2024 aluminium alloy consolidated from nanocrystalline alloy powders via hot hydrostatic extrusion

Abstract

Nanocrystalline 2024 aluminium alloy powders with an average grain size less than 50 nm, prepared by a unique technique which combines rapid solidification and mechanical milling, were consolidated into bulk material under various technical conditions via hot hydrostatic extrusion and the microstructure and mechanical properties of the consolidated alloy were experimentally investigated. The influence of the two main technical parameters, extrusion ratio and temperature, on the microstructure and mechanical properties of the as extruded alloy is made clear and the reasons why these two parameters had such an influence on the microstructure and mechanical properties of the alloy are also discussed. Furthermore, suggestions are given for rationalising the extrusion ratio and temperature for the consolidation of the nanocry stalline 2024 aluminium alloy powders via hot hydro static extrusion.     

Structure and mechanical characteristics of preliminarily deformed welded joints of the 40KKhNM alloy

The results of investigating the structural state and the variation in mechanical characteristics during the static and cyclic loading of deformed welded joints of the 40KKhNM alloy are presented. It is shown that quenching eliminates structural-and-mechanical nonuniformity. The formation of ? martensite can introduce an essential contribution to alloy hardening because of the development of the γ → ? transformation during tensile static deformation. It is established that the fatigue characteristics vary insignificantly depending on the degree of preliminary deformation. Production modes that provide the maximal fatigue strength with a minimal accumulation intensity of cyclic damages of welded joints are determined.     

微量Sc、Zr和Er对5182铝合金焊缝组织与性能的影响

在ER5356铝合金焊丝中添加了微量的Sc、Zr和Er,制备出微合金化ER5356铝合金焊丝.使用微合金化焊丝焊接4 mm厚的5182铝合金板材,焊接采用手工钨极惰性气体保护焊.利用金相显微镜,X射线衍射以及透射电镜研究了微量的Sc、Zr和Er对5182铝合金焊缝处显微组织的影响.结果表明,在ER5356铝合金焊丝中添加的Sc、Zr和Er可以有效改善5182铝合金板材焊后焊缝处的显微组织,显著细化组织晶粒.其中,ER5356铝合金焊丝中单独添加0.3%Sc焊后效果最佳.     

Mechanical properties of the welded joints of 1565ch alloy sheets at low temperatures

The effect of the method of welding on the mechanical properties of the welded joints of the 1565chM alloy is studied at room, high, and low temperatures.     

半固态粉末轧制法制备SiC_p/AA2024复合带材的显微组织与力学性能

以组合雾化法制备的2024铝合金粉末和SiC颗粒为原材料,采用半固态粉末轧制法,在575~635℃温度下制备10%SiC_p/AA2024复合带材,研究粉末加热温度对带材显微组织与力学性能的影响,并与相同条件下制备的AA2024铝合金带材进行对比。结果表明:升高粉末加热温度可促进AA2024粉末变形或破碎,所得10%SiC_p/AA2024复合带材具有半固态特征的球状或近球状显微组织。与AA2024合金带材相比,SiC_p/AA2024复合带材的基体晶粒更加细小。SiC颗粒与液相Al没有发生显著的界面反应,未生成对体系有害的Al4C3物质。SiC_p/AA2024复合带材和AA2024合金带材的屈服强度、抗拉强度及伸长率都随粉末加热温度适当升高而提高,SiC_p/AA2024带材的屈服强度和抗拉强度分别在366~412 MPa和425~514 MPa之间,均明显高于AA2024合金带材,伸长率为3.1%~4.9%,断裂方式主要为脆性断裂。AA2024带材的屈服强度在265~348 MPa范围内,抗拉强度为362~423 MPa,拉伸断裂方式随加热温度升高由脆性断裂向韧性断裂转变。     

Study on microstructure and mechanical properties of spark plasma sintered Alumix 431 powder

Spark plasma sintering (SPS) has been used to successfully densify a 7075 aluminium alloy obtained from Alumix 431 powder. Sintering experiments were conducted at the temperature of 450 and 500°C for 2.5, 5 and 10?min. All the presented results confirm the excellent sinterability of Alumix 431 powder in vacuum during the SPS process and clearly show the effect of sintering temperatures and holding times on the densification, microstructure and mechanical properties of the obtained sintered compacts. The best results of hardness (1412?±?39?MPa), tensile strength (345?±?15?MPa) and compressive strength (618?±?4?MPa) were obtained by the compacts sintered at 500°C for 5 min.     

断续节理对岩体力学性能的影响

采用颗粒流数值模拟程序,建立不同节理状态的岩石试样模型,对其进行双轴试验模拟,从岩桥长度、节理长度和倾角三个方面对断续节理影响下的岩体破裂形式和力学性质进行了数值模拟分析.岩桥的破裂方式为翼裂纹扩展下的拉剪复合破坏,模型破裂大致经历了翼裂纹的扩展、次生裂纹的延伸以及岩桥的贯通三个过程,而且表现出明显的蠕变特性以及延性破坏.岩桥长度的变化对峰值强度和弹性模量影响较小;相比岩桥长度,节理岩样的力学特性对节理长度更加敏感.对于不同的节理倾角,岩石试件表现出不同的初始破裂形式,0°倾角岩样的破裂方式为翼裂纹的扩展和次生裂纹的延伸,中间岩桥没有被贯通,15°倾角岩样的初裂强度和峰值强度最大.     

Properties of the welded joints of manganese steel made by low-frequency pulsed arc welding

The structure, the mechanical properties, the impact toughness, and the fracture mechanisms of the welded joints made of steel 09G2S plates by direct current welding and pulsed arc welding with a modulated arc current in the frequency range 0.25–5.0 Hz are studied. The application of low-frequency pulsed arc welding allowed us to form welded joints with a fine-grained structure in the weld metal and the heat-affected zone and to achieve a higher impact toughness and a longer cyclic fatigue life as compared to the welded joints fabricated by direct current welding. The achieved effect manifests itself over the entire testing range from 20 to–60°C.     

铝合金焊接性能及焊接接头性能的研究

在高铁、地铁列车的制造中,铝合金材料更是列车车体的主要材料之一,然而由于铝合金材料在焊接性能、焊接接头性能方面仍存在一定的不足,经常会出现气孔、裂纹等缺陷,因此高铁、地铁列车铝合金车体的焊接施工质量仍然很难保证。本文对铝合金的焊接性能以及焊接接头性能进行了分析。