Influence of Mg and Si Content in Aluminium Alloys on Severe Plastic Deformation Behaviour during Solid-State Coating Deposition using Friction Surfacing

铝合金中 Mg 和 Si 含量对摩擦堆焊固态涂层沉积过程中严重塑性变形行为的影响

基本信息

批准号：
323162991
负责人：
Dr.-Ing. Stefanie Hanke
金额：
--
依托单位：
Lehrstuhl für Werkstofftechnik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/323162991?language=en
关键词：
Influence Mg Si Content Aluminium

项目摘要

Dynamic recrystallization has a major influence on process characteristics and material flow in friction-based solid state joining techniques. In addition to general material properties, a.o. heat capacity and high temperature strength, dynamic microstructural processes, e.g. dislocation movement, grain boundary migration, formation of substructures or precipitation of phases, have a strong effect on the acting flow stresses. The correlation of such microstructural mechanisms and the material behaviour during Friction Surfacing or similar solid state joining techniques has not been systematically investigated up to today. Small changes in the content of alloying elements, e.g. in Aluminium alloys, require significant adaptations of the process parameters, which are to date established by empirical or statistical approaches.During Friction Surfacing (FS), a stud made from the coating material, rotating around its longitudinal axis, is pressed onto the substrate. After a short heating phase (< 2 s), the stud material adheres to the substrate surface and the rotational relative motion is accommodated by shearing the softened stud material. When an additional translational motion is superimposed, the plastified stud material is sheared off the stud and deposited onto the substrate as a coating layer. The heat required for the process is solely generated from plastic deformation.For FS of Aluminium alloys, rotational speeds up to 4000 1/min are applied, process temperatures reach approximately 80% of the melting temperature and cooling rates range at 30 K/s. Although strain and strain rates can only be estimated from the dimensions of the shear layer, obviously the deformation conditions are extreme. The available knowledge of dynamic recrystallization and flow stresses under such severe conditions is very limited, and only few publications on Gleeble-tests and high-pressure-torsion experiments at high temperatures provide some clues.In the scope of this project 6 custom-made Aluminium alloys are processed by FS. Each of these alloys only differs in its content of Mg or Si, allowing a direct comparison and therewith the investigation of the effects of those alloying elements on the material behaviour. The Si content will be raised up to 17.5 wt%, providing undissolvable hard phases during processing, which will further influence the deformation and recrystallization mechanisms. Besides examining process forces and coating geometry, XRD, EBSD and TEM investigations of the microstructural mechanisms of plastic deformation will be carried out, and correlated with the material behaviour during FS.FS typically results in very low grain sizes and spheroidization of hard phases. The mechanical properties of the obtained coatings, which are relevant for a potential industrial application of the FS process to generate coatings via severe plastic deformation, will be evaluated through micromechanical tests in the scope of this project.

动态再结晶对基于摩擦的固态连接技术中的工艺特性和材料流动具有重大影响。除了一般材料特性外，a.o.热容量和高温强度、动态微观结构过程，例如位错运动、晶界迁移、亚结构的形成或相的沉淀对作用的流应力有很大的影响。迄今为止，这种微观结构机制与摩擦堆焊或类似固态连接技术中材料行为的相关性尚未得到系统研究。合金元素含量的微小变化，例如在铝合金中，需要对工艺参数进行重大调整，这些参数迄今为止是通过经验或统计方法确定的。在摩擦堆焊 (FS) 过程中，由涂层材料制成的螺柱绕其纵轴旋转，被压到基材上。经过短暂的加热阶段（< 2 秒）后，螺柱材料粘附到基板表面，并通过剪切软化的螺柱材料来适应旋转相对运动。当叠加额外的平移运动时，塑化的螺柱材料从螺柱上剪下并作为涂层沉积到基材上。该工艺所需的热量仅由塑性变形产生。对于铝合金的 FS，采用高达 4000 1/min 的转速，工艺温度达到熔化温度的约 80%，冷却速率范围为 30 K/s。虽然应变和应变率只能根据剪切层的尺寸来估计，但显然变形条件是极端的。在如此恶劣的条件下，关于动态再结晶和流动应力的现有知识非常有限，只有少数关于高温下的 Gleeble 测试和高压扭转实验的出版物提供了一些线索。在该项目的范围内，有 6 个定制铝合金由FS加工。这些合金中的每一种仅在镁或硅含量上有所不同，因此可以直接比较并研究这些合金元素对材料行为的影响。 Si含量将提高至17.5 wt%，在加工过程中提供不可溶的硬质相，这将进一步影响变形和再结晶机制。除了检查工艺力和涂层几何形状外，还将对塑性变形的微观结构机制进行 XRD、EBSD 和 TEM 研究，并与 FS 期间的材料行为相关。FS 通常会导致非常低的晶粒尺寸和硬相的球化。所获得涂层的机械性能与 FS 工艺通过严重塑性变形生成涂层的潜在工业应用相关，将通过本项目范围内的微观机械测试进行评估。