Friction stir welding of dissimilar sheet materials

异种板材搅拌摩擦焊

• 批准号: RGPIN-2014-04857
• 负责人: Gerlich, Adrian
• 金额: $ 1.82万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=638138
• 关键词: Friction; stir; welding; dissimilar; sheet

There has been a growing need for improved fuel efficiency in the transportation industries, and this has motivated weight reductions through increased utilization of light-weight materials such as aluminum and magnesium alloys, and composites. However, during component fabrication the main challenge is welding of these materials, particularly when dissimilar combinations are encountered. Even similar alloy joining is not trivial, due to cracking, solidification porosity, and severe distortion during arc welding. Joints involving fiber reinforced polymer composites typically require fasteners or adhesives, which are more costly and time-consuming than welding. In recent years, the process of friction stir welding has emerged as a solid state welding technique which offers many advantages and new capabilities compared to fusion welding. The main feature of solid state welding is that many of the traditional problems like cracking and porosity are avoided by keeping materials below the melting point. The friction stir welding technique uses a cylindrical shaped tool with a pin shaped protrusion at the end, which is traversed along the materials to be joined, either in a lap weld or butt joint configuration. This proposal examines a variation of friction stir welding in which spot welding can be conducted using a pin that retracts into the cylindrical tool. Only a few studies have been reported on this so-called ‘refill friction stir spot welding’ approach, however it has been demonstrated that superior joint strength can be achieved compared to traditional friction stir spot welding. The process may be applied to dissimilar material combinations, and the main focus of this work is joining aluminum to fiber reinforced composite sheets. The objective will be to determine factors which control bonding during refill friction stir spot welding of these materials, and to identify processing parameters or possible interlays that provide higher joint strengths. A specialized refill friction stir welding system will be used to study the mechanisms of joint formation in thin sheet spot welds. The details of bonding in terms of reactions, intermixing, and mechanical interlocking will be compared to the welding parameters. Advanced electron microscopy techniques will be applied to evaluate the role of temperature and stress on bond formation. The properties of the joints will be investigated using overlap shear testing, as well as instrumented indentation testing using both macro-scale and nano-indentation techniques. This will allow overall joint strengths to be correlated with microscopic features and phases which form during welding. The proposed work will generate knowledge that is required in order to promote widespread implementation of this technology in industry. Since time, temperature, pressure and deformation control the joint strength, the role of each parameter needs to be understood. A thorough study of the interfacial bonding will help to identify which parameters dominate and contribute most significantly to joint strengths. The proposed work will allow processing maps to be developed for this technique which may also have applicability to other solid state joining processes, including conventional friction stir welding. These maps can be later utilized by the Canadian industries in order to rapidly develop solutions for joining difficult combinations by connecting processing parameters to the desired microstructures which provide highest strength. This will help transportations industries utilize advanced solid state joining technologies in order to increase their capabilities and reduce fabrication costs.

运输行业的燃油效率越来越不断提高，这通过增加了轻重量材料（例如铝和镁合金以及零件）的利用来减轻重量。但是，在组件制造过程中，主要挑战是这些材料的焊接，尤其是在遇到不同的组合时。由于开裂，固化孔隙度和电弧焊接过程中的严重变形，即使是类似的合金连接也不是微不足道的。涉及纤维增强聚合物公司的关节通常需要紧固件或粘合剂，而固定器或胶粘剂比焊接更昂贵和耗时。近年来，摩擦搅拌焊接的过程已成为一种固态焊接技术，与融合焊接相比，它具有许多优势和新功能。固态焊接的主要特征是，通过将材料保持在熔点以下，可以避免许多传统问题，例如破裂和孔隙率。摩擦搅拌焊接技术使用圆柱形工具，末端带有销钉形蛋白，沿着材料沿材料横穿，无论是在膝盖焊缝还是对接接头构型中。该提案检查摩擦搅拌焊接的变化，在该旋转焊接中，可以使用将插头缩回到圆柱形工具中的销钉进行斑点焊接。关于这种所谓的“补充摩擦搅拌点焊接”方法，只有少量研究报道了，但是与传统的摩擦引人注目的焊接焊接相比，已经证明可以实现较高的关节强度。该过程可以应用于不同的材料组合，这项工作的主要重点是将铝与纤维增强复合材料片连接在一起。目的是确定这些材料的重新摩擦打击斑点焊接过程中哪些控制键的因素，并确定加工参数或可能提供更高关节强度的可能性。专门的补充摩擦搅拌焊接系统将用于研究薄片点婚礼中关节形成的机制。在反应，混合和机械互锁方面的粘结细节将与焊接参数进行比较。高级电子显微镜技术将用于评估温度和应力对键形成的作用。将使用重叠剪切测试以及使用宏观尺度和纳米识别技术的仪器凹痕测试来研究关节的性能。这将使总体关节强度与在焊接过程中形成的显微​​特征和相位相关。拟议的工作将产生所需的知识，以促进该技术在行业中的广泛实施。由于时间，温度，压力和变形控制关节强度，因此需要了解每个参数的作用。对界面键合的透彻研究将有助于确定哪些参数占主导地位，并最大程度地促进关节强度。拟议的工作将允许为此技术开发处理图，该技术也可能适用于其他固态加入过程，包括常规摩擦搅拌焊接。这些地图以后可以被加拿大行业使用，以便通过将处理参数连接到提供最高强度的所需的微观结构来快速开发解决困难组合的解决方案。这将有助于运输行业利用先进的固态加入技术，以提高其能力并降低制造成本。