The quantitative investigation of mechanical properties and characterization of fractured position for friction stir lap welded A6111/A5023

The effects of plunge depth (PD) revolutionary pitch (RP) and materials arrangement on deformation and softening material at the fractured position of a friction stir welded AA6111 to AA5023 lap joint were investigated. As a result, the main factor determining tensile shear load and fracture was different with the location of soft material. When the soft material was located on top, the softening material and the deformed surface height occurred by friction heat generation of the rotating shoulder. The main factor was the deformed surface height rather than the softening material, and the deformed surface height was decreased with increasing RP. On the other hand, when the soft material was located at the bottom, the movement of the un-bonded line and hooking occurred due to the vertical flow of the rotating probe. The crucial factor was the position of the un-bonded line rather than the height of the hook. The un-bonded line occurred along the interface between two materials affected by the lowest strength, which were deformed toward the hard material affected by a higher joint strength.     

Q235钢镀锌层对钢/铝合金搅拌摩擦点焊接头性能的影响

通过在Q235钢板上电镀不同厚度的锌层,研究镀锌层厚度对钢/铝合金异种金属搅拌摩擦点焊接头性能的影响。利用拉剪试验、光学显微镜、扫描电子显微镜等分析手段对钢/铝合金异种金属搅拌摩擦点焊接头性能进行了分析。结果表明,镀锌层厚度在8~12μm的Q235镀锌钢与6061铝合金形成的点焊接头拉剪力较高。     

Effect of rotation speed on microstructure and mechanical properties of bobbin tool friction stir welded AZ61 magnesium alloy

The 5-mm-thick AZ61 magnesium alloy was friction stir welded by using the specially designed bobbin tool with various rotation speeds. Defect-free welds were successfully obtained with rotation speed ranging from 550 to 600?rev?min^?1. Grain size in different regions of the joints varied depending on the rotation speed. The hardness value of the joint is uniform. The defective joint fractured in the weld nugget zone with the lowest tensile strength, while the fracture location of the defect-free joints changed to the heat affected zone. The impact energy of weld nugget zone is higher than that of the heat affected zone, and the impact energy of the two zones in defect-free joint both decreased with increasing rotation speed.     

Friction stir welding of thick section reduced activation ferritic–martensitic steel

Full penetration friction stir welding was conducted on 12?mm thick reduced activation ferritic–martensitic steel at tool rotational speeds of 500 and 900?rev?min^?1. Comparator welds at 500?rev?min^?1 were also produced in 6?mm thick reduced activation ferritic–martensitic steel plate to evaluate section thickness effects. Increase in section thickness led to an increase in heat input, which strongly influenced the microstructure evolution in stir zone (SZ), thermo-mechanical affected zone and the overall hardness in the SZ of this steel. In the as-welded condition, the base metal microstructure was significantly altered and resulted in carbide-free grain boundaries. The desirable microstructure and mechanical properties were achieved by subjecting the as-welded joints to appropriate post-weld heat treatments.     

Experimental and thermomechanical analysis of friction stir welding of poly(methyl methacrylate) sheets

In the present work, the feasibility of friction stir welding (FSW) of poly(methyl methacrylate) sheets was studied experimentally and theoretically by employing thermomechanical simulations. The effect of processing parameters including tool plunge depth, tilt angle, tool rotational speed (w), and transverse velocity (v) was investigated to determine suitable conditions to attain sound and defect-free joints. It is shown that a low tool plunge depth of 0.2?mm and a tilt angle of 2° provide suitable material flow to gain sound joints. By controlling the heat input into stir zone by increasing the tool rotational speed and decreasing linear velocity, the formation of defects can be minimised. Mechanical examinations in both longitudinal (LS) and transverse (TS) directions indicate that the highest joint strength of 57?MPa (for LS) and 42?MPa (for TS) are obtained at processing conditions of w?=?25?mm?min^?1 and v?=?1600?rev?min^?1. The measured tensile strengths are 81 and 60% of the base polymer, respectively.     

Friction stir scribe welding technique for dissimilar joining of aluminium and galvanised steel

Friction stir scribe technology, a derivative of friction stir welding, was applied for the dissimilar lap welding of an aluminium alloy and galvanised mild steel sheets. During the process, the rotating tool with a cobalt steel scribe first penetrated the top material – aluminium – and then the scribe cuts the bottom material – steel. The steel was displaced into the upper material to produce a characteristic hook feature. Lap welds were shear tested, and their fracture paths were studied. Welding parameters affected the welding features, including hook height, which turned out to be highly related to fracture position. Therefore, in this paper, the relationships among welding parameters, hook height, joint strength and fracture position are presented. In addition, the influence of zinc coating on joint strength was also studied.     

Realising equal strength welding to parent metal in precipitation-hardened Al–Mg–Si alloy via low heat input friction stir welding

Two millimetres thick Al–Mg–Si (6061Al-T6) alloy plates were friction stir welded at various welding conditions. Under a low rotation rate of 400?rev?min^–1 with rapid water cooling, the softening zone in the joint disappeared and a nanostructure with an average grain size of 80?nm was obtained in the stir zone (SZ). Therefore, a weld with equal strength to the parent metal (PM) was successfully achieved with the fracture occurring in the PM. Further, the average microhardness and ultimate tensile strength (UTS) of the SZs increased with the decreasing rotation rate and increasing cooling speed. The average microhardness and UTS of the SZ with nanostructure reached up to 134?HV and 505?MPa, respectively; though the initial strengthened precipitates disappeared. This work provides an effective strategy of achieving high property joints and enhancing the mechanical properties of precipitation-hardened Al alloys.     

搅拌摩擦焊温度场数值模型的研究进展

针对搅拌摩擦焊(FSW)的一个主要研究方向是探讨焊接过程中温度场的演变规律。在研究温度场时,数值模拟方法具有试验方法难以替代的优势。回顾了针对FSW温度场进行数值模拟时涉及到的主要模型、它们的大体思路以及各自的特点,重点论述了其中的产热和传热模型。在产热模型中,讨论了与热输入有关的热源模型、产热量计算模型和接触模型;在传热模型中,分别从热传导、对流换热和热辐射等方面进行了分析。此外,考虑到某些材料属性对温度场模拟结果的影响,文章的最后也对其进行了简要讨论。     

搅拌摩擦加工参数对5083铝合金组织性能的影响

采用搅拌摩擦加工方法对不同焊接参数下的退火态5083铝合金的组织和性能进行研究.通过显微硬度实验研究了硬度在前进侧和后退侧以及加工区上下部分的分布规律;通过金相观察研究了加工区表面带状纹理和腐蚀后观察到的弧纹之间的关系.对母材和加工区用扫描电镜观察了析出相的形貌、尺寸及分布规律.结果表明:高硬度区宽度随着轴肩直径的增大而增大,随着转速和焊速之比(ω/ν)的增加而增大,硬度在前进侧(AS)和后退侧(RS)的分布是不均匀的;从母材到加工区硬度逐渐上升,RS侧的上升速度约为AS侧的一半.     

搅拌摩擦加工及后续热处理对7B04-O铝合金组织和硬度的影响

对7B04-O铝合金进行搅拌摩擦加工,对不同旋转速度参数下获得的7B04-O铝合金搅拌区的组织和硬度进行研究,同时利用后续热处理改善搅拌区的组织和硬度.研究表明,搅拌摩擦加工导致搅拌区的晶粒细化,硬度提升.不同的旋转速度会对后续热处理造成影响.采用低转速时,后续热处理不能进一步提高搅拌区的硬度;而采用高转速时,搅拌区的硬度则可以通过后续热处理得到提升.采用O态铝合金作为母材时,基体内的原始析出强化相尺寸粗大,热稳定性较高,难以在搅拌摩擦加工过程中充分溶解.通过提高转速来增加加工热输入可以增加析出相的溶解量,有利于后续热处理对组织和硬度的改善.