Ultrasonic spot welding of Al/Mg/Al tri-layered clad sheets

Solid-state ultrasonic spot welding (USW) was used to join Al/Mg/Al tri-layered clad sheets, aiming at exploring weldability and identifying failure mode in relation to the welding energy. It was observed that the application of a low welding energy of 100 J was able to achieve the optimal welding condition during USW at a very short welding time of 0.1 s for the tri-layered clad sheets. The optimal lap shear failure load obtained was equivalent to that of the as-received Al/Mg/Al tri-layered clad sheets. With increasing welding energy, the lap shear failure load initially increased and then decreased after reaching a maximum value. At a welding energy of 25 J, failure occurred in the mode of interfacial failure along the center Al/Al weld interface due to insufficient bonding. At a welding energy of 50 J, 75 J and 100 J, failure was also characterized by the interfacial failure mode, but it occurred along the Al/Mg clad interface rather than the center Al/Al weld interface, suggesting stronger bonding of the Al/Al weld interface than that of the Al/Mg clad interface. The overall weld strength of the Al/Mg/Al tri-layered clad sheets was thus governed by the Al/Mg clad interface strength. At a welding energy of 125 J and 150 J, thinning of weld nugget and extensive deformation at the edge of welding tip caused failure at the edge of nugget region, leading to a lower lap shear failure load.     

Investigation on formability of three-layer joined Al/Cu/Al sheets annealed at different temperature

ABSTRACT

Today, the use of multi-layer sheets has expanded widely in various industries. The determination of the forming limit curve for sheets is essential. In this project, three-layer aluminium1100-copper10100-aluminium1100 sheet was produced using an explosive welding method and cold rolling up to 85% strain. Then to eliminate the rolling microstructure and create the isotropic properties and to investigate the effect of annealing temperature on formability, three-layer sheets were annealed at 350°C, 400°C, and 450°C for one hour. Afterward, the numerical and experimental forming limits for these sheets are obtained at room temperature. ABAQUS finite element software and Freudenthal, Cockcroft, and Brozzo ductile fracture criteria were used in numerical method, and punch stretching test was used in the experimental method.     

Experimental investigation and finite element modeling on profile forming of conical component using Al 3003(O) alloy

Profile forming of sheet metal is a special technique that offers flexibility and cost-effectiveness in the metal forming process, requiring no high capacity presses or set of dies, thus meeting the ever increasing demand for small batch production and rapid prototyping. This paper demonstrates the formation of sheet metal part using the CNC controlled hemispherical tool and analyses the various parameters underlying this mechanism – like maximum wall angle, surface roughness (Ra) and thinning of sheet. Analysis of the microstructure is carried out using Scanning electron microscopy and Energy-dispersive X-ray spectroscopy microanalysis test. In this study, Aluminum sheet of grade Al 3003(O) with 1 mm and 1.25 mm thickness is used as a work piece. The paper also presents an explicit numerical simulation using the standard finite element code ABAQUS and the experimental and numerical results are validated.     

Interfacial characteristics of Zn/AZ31/Zn clad sheets fabricated by hot roll-bonding and annealing

The Zn/AZ31/Zn tri-layer clad sheets are prepared by hot roll-bonding technology and post-roll annealing in this study and the interfacial microstructure, mechanical and corrosion properties are investigated. The annealing temperature can influence the interfacial bonding behaviour. Upon annealing at 200°C, a good metallurgical bonding interface composed of Mg₄Zn₇ and MgZn₂ phases is obtained. A higher temperature (300°C) can induce the precipitation of the brittle Mg₂Zn₁₁ phase at the interface. The clad sheets annealed at 200°C can attain the maximum bonding strength among all the clad sheets investigated. Importantly, the corrosion rate can be obviously reduced by cladding pure Zn layer on both sides of AZ31 alloys, which provides another effective method to improve the corrosion resistance of magnesium alloys.     

Microstructure design and dissolution behavior between 2024 Al/Sn with the ultrasonic-associated soldering

Here we present recent progress on α-Al dendrite-reinforced joints of 2024 aluminum produced by the ultrasonic-assisted soldering method. In ultrasonic-assisted soldering of Al2024, pure Sn was utilized as a filler metal, the vibration frequency was 21 kHz, and the temperature was 300 °C. Interestingly, the aluminum content in the bond was up to 3.2 mass%, which is much higher than the solubility limit of aluminum in Sn at 300 °C. The evolution of the microstructure of the aluminum dendrites in bonds with different ultrasonic time was observed to investigate the dissolution behavior of 2024 Al in Sn under ultrasonic conditions. A migration model of aluminum dendrites in the bonds is proposed, which enables control of the extent of reinforcing α-Al dendrites by varying the ultrasonic time. The shear strength of the α-Al dendrite-reinforced joints is improved significantly, with the maximum shear strength approaching 60 MPa.     

Spinodal decomposition in Al/Zn alloys

The effect of spinodal decomposition on the mechanical behaviour of Al/Zn alloys was studied over the range of 30 to 60 wt % zinc. Two solution treatment temperatures, 365 and 435° C, were used; extensive ageing studies were carried out at 22 and 100° C, and limited tests were made on samples aged at other temperatures, 0, 55, and 200° C. The yield and tensile strengths were significantly increased by spinodal transformation, but ductility was seriously impaired. The tensile fracture was intergranular, with one exception, and was related to grain-boundary precipitation and a narrow denuded zone.Calculated yield strengths based on Cahn's analysis did not agree with those derived from the correct dislocation model. The wrong model did give fortuitous agreement. Spinodal hardening appears to offer a promising new hardening mechanism in aluminium alloys if the particular composition and treatment can be found to eliminate the serious lack of ductility.     

等通道转角变形对铸态3003铝合金夹杂物的影响

本文在室温下对铸态3003铝合金实施了道次等效应变约为0.5的等通道转角变形(Equal-channel angular pressing-ECAP),对其夹杂物的碎化、分布和合金的硬度进行了考察。结果表明,第1道次的ECAP加工将合金内部的粗大(长5-15μm、宽1-2μm)且几乎呈连续分布的夹杂物(AlFe(Mn)Si)折断碎化(长1-3μm)并初步分散开,引入大量位错至合金中,提高硬度幅度达66.7%。后续的2-4道ECAP加工将夹杂物分散均匀,但对夹杂物的碎化和硬度影响很小。本文的试验结果说明了ECAP作为一种细化铝合金内部AlFe(Mn)Si夹杂物并使之分布均匀的工艺方法的可行性。     

Zn—5Al合金铸态共晶结构的研究

利用光学显微镜、扫描电镜、透射电镜研究了Ｚｎ－５Ａｌ合金的铸态共晶结构。结果表明，Ｚｎ－５Ａｌ合金的铸态组织为典型的片层状共晶共析结构，其特征可表示为β（α│β│α）β，其中β为Ｚｎ基固溶体，α为Ａｌ基固溶体；括号外的β表示共晶结构中的较宽片层，直接来源于共晶反应，括号内的部分表示共晶结构中的较窄片层，是由α和β两相组成的共析产物，是由α和β两相组成的共析产物，其中α相包裹着β相。     

高强钢冷喷涂铝锌复合涂层性能研究

采用冷喷涂技术在高强钢(300M)表面制备铝锌复合涂层作为抗腐蚀涂层.利用扫描电镜(SEM)、能量色散谱(EDS)、显微硬度测试仪研究涂层的微观形貌结构及显微硬度;综合涂层中性盐雾加速实验及户外暴晒实验结果并与300M基材进行对比,对涂层的抗腐蚀性能开展全面评价;考核冷喷涂后对300M钢基材疲劳性能影响.结果表明:冷喷涂铝锌复合涂层结构致密,平均孔隙率为0.8％,显微硬度为59.8HV0.025,中性盐雾实验1000h时无腐蚀,即使涂层破损也可以达到770h,户外大气暴晒实验12个月后涂层表面无腐蚀发生,冷喷涂后对300M钢基材的疲劳性能没有影响.     

Microstructure and mechanical properties of Mg–Al–Zn alloy sheets severely deformed by accumulative roll-bonding

The as-rolled AZ31 Mg alloy sheets were subjected to accumulative roll-bonding (ARB) at 300 °C up to three cycles. The microstructure and macro- texture are investigated by means of optical microscopy and X-ray analysis. The mechanical properties are evaluated by micro-hardness and tensile tests. Very fine grain size of 2.4 μm could be achieved after three passes of 50% thickness reduction. The recrystallized structure was already formed after one cycle of ARB. ARB processing resulted in a significant increase of ductility and slight decrease of tensile strength of the AZ31 alloy sheet. Basal texture was notably weakened after ARB processing.     

An experimental investigation into the warm deep-drawing process on laminated sheets under various grain sizes

It has been proved by many researchers that increasing the temperature in warm deep-drawing process of single layer sheets decreases the forming load, however, this phenomenon is not necessarily the case in warm deep-drawing process of laminate sheet. The objective of the present paper is to carry out a comprehensive investigation on warm deep-drawing process on laminated sheets experimentally. Based on the results of this study, it can be observed that by raising the temperature, variation of forming load more depends on blank holder force (BHF). In this study, thinning and wrinkling in Al 1050/St 304 and Al 5052/St 304 samples for each layer in warm deep-drawing process are evaluated individually. In addition, the effects of various grain sizes, blank temperatures and sequence layer on forming load are investigated. In order to carry out a comprehensive survey of warm deep-drawing; three blank temperatures namely, 25 °C, 100 °C and 160 °C are examined. Furthermore, to achieve various grain sizes, the aluminum sheets are annealed at 350 °C, 400 °C and 450 °C for 1 h. Finally, several tests are conducted to obtain the influences of grain size on some material characteristics such as stress, elongation and friction coefficient.     

Al和Zn周期性层片状组织的形成

为探讨A l粉和Zn粉形成周期性层片状组织的机理,采用粉末烧结方法,在不同粉末配比、烧结温度、保温时间、压制方式和冷却方式条件下,利用光学显微镜、扫描电子显微镜和X射线衍射技术,研究了A l-Zn周期性层片状组织的微观形貌和相组成.研究发现,在A l粉和Zn粉固相成型和烧结过程中,提高烧结温度、延长保温时间以及增加粉末颗粒接触界面都可以促进A l/Zn周期性层片状组织的形成;压制和冷却方式不影响A l/Zn周期性层片状组织的形成.A l粉和Zn粉通过固相反应扩散直接形成周期性层片状组织.     

Optimization of GTAW Al 3003 weld using fabricated nanocomposite filler metal

Novel Al–3 wt.% TiO₂ (fillers) nanocomposite has been successfully fabricated by accumulative roll bonding method to join Al 3003 alloy with the parameters of gas tungsten arc welding process such as the shielding gas flow rate (G), the welding speed (S), and the current (I) identified by response surface methodology. After preparation of weldment, studies involving X-ray diffraction and advanced electron microscopy techniques (scanning electron microscope and transmission electron microscope) have been carried out. FESEM has revealed the presence of second-phase hard ceramic particles which are embedded homogeneously in the matrix material. Energy dispersive spectroscopy analysis indicates the absence of foreign particles other than Al, Ti, and oxides. Further, the results show that the increase in mechanical properties (hardness and ultimate tensile strength) of the weldment is due to grain refinement and uniform distribution of TiO₂ nanoparticles. The analysis of variance test identified the welding speed as a significant parameter on the homogeneous distribution of TiO₂ particles followed by current and gas flow rate in sequential order.     

Stabbing of metal sheets by a triangular knife. An archaeological investigation

In order to provide a basis for comparative evaluation of ancient and early modern metal armour, experiments have been made with a simplified knife to investigate the action of stabbing into thin metal sheets. The forces required for indentation, perforation and extension of the slit were measured for sheets simply supported over a circular hole. A range of metals in different thermomechanical states, with Vickers hardnesses from 5 to 200 VPN and fracture toughnesses (crack-tip opening displacements) from 0.4 to 1.5 mm, and thicknesses from 0.5 to 2 mm, was employed. The behaviour of the simplified knife could be modelled approximately using the analysis by Wierzbicki and co-workers (Int. J. Mech. Sci. 35 (1993) 209; Int. J. Impact Eng. 19 (1997) 667) for loading a thin plate edge-on by a wedge. The results demonstrate that it is possible to rank the protective value of early armour in different metals, using readily determined mechanical properties.     

预处理工艺对双辊铸轧3003铝合金再结晶行为的影响

对双辊铸轧3003铝合金板材进行了3种预处理退火,研究不同预处理工艺下的冷轧板材在380～500℃退火时晶粒组织和再结晶织构的变化规律。结果表明:最优化预处理工艺为610℃/12h+460℃/12h,高温阶段第二相尺寸发生粗化,低温阶段基体中Mn的过饱和固溶度显著降低,两者均有利于提高后续退火时的再结晶形核率。500℃退火时,在粗大第二相的附近产生了粒子诱发形核机制,降低了再结晶织构强度;并且退火时几乎不存在析出,析出相对再结晶形核的抑制作用甚微,从而得到了晶粒细小、织构弱的再结晶组织。     

Microstructure of Al/Al bimetallic composites by lost foam casting with Zn interlayer

A novel method named the lost foam casting (LFC) liquid–liquid compound process with a Zn interlayer was proposed to prepare the Al/Al bimetallic composites, and the microstructure of the Al/Al bimetallic composites was investigated in the present work. The results showed that the Al/Al bimetallic composites were successfully produced using the novel process. The Zn interlayer prevented different liquid metals from directly mixing. A uniform and compact metallurgical interface was obtained between the Al and the A356 aluminium alloy, which consisted of the η-Zn, α-Al rich, α?+?η eutectoid, and primary silicon phases. The microhardness of the interface layer was significantly higher in comparison with those of the Al and A356 matrixes.     

Evolution of strain states and textures during roll-cladding in STS/Al/STS sheets

The evolution of strain states and textures during roll-cladding of three plies of sheets comprising ferritic stainless steel (STS), aluminum (Al) and ferritic stainless steel was investigated by measurements of crystallographic textures and by simulations with the finite element method (FEM). Because the deformation mainly occurs in the Al layer during roll-cladding, the present investigation was focused on the Al layer located at the middle of clad samples. Roll-cladding of STS/Al/STS sheets led to the development of a strong through thickness texture gradient in the Al sheet which was characterized by shear textures at the surface layer and rolling textures at the center layer. The temperature of the cladding operation played an important role in the evolution of textures.