Influence of trace elements with high vacancy binding energy on the precipitation hardening of Al-Cu-alloys

高空位结合能微量元素对Al-Cu合金沉淀硬化的影响

• 批准号: 275221441
• 负责人: Professor Dr.-Ing. Bernd Kieback
• 金额: --
• 依托单位: Institut für Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/275221441?language=en
• 关键词: Influence; trace; elements; vacancy; binding

AlCu-based alloys have important applications as high-strength light-weight materials for the fuselage in aviation (AlCuMg, AlCuLi) and as cast-alloys (AlSiCu) for engine blocks in the transport sector. However, adding trace elements to these alloys can significantly improve their strength, while the underlying atomic mechanisms of nucleation are so far only superficially understood. Increasing strength (age-hardening) in aluminium based materials is based on the vacancy-diffusion-controlled formation of precipitates during or immediately after the heat treatment of aluminium alloys. Hence, a high vacancy-binding energy of trace elements has a decisive influence on the precipitation process. In this project we are going to study the influence of trace elements (< 0.1 at% of e.g. In, Sn, Sb, Pb, Bi) on the nucleation and, thus, on the age-hardening behaviour resp. strength of AlCu-based alloys from pure elements. The aim of this project - concerning trace elements - is to understand basic aspects of their vacancy-binding phenomenon as a function of their concentration and their binding strength in aluminium alloys. To reveal the complex interplay between alloying as well as trace elements with quenched-in vacancies from the heat treatment, we will employ several complementary methods including simulation tools. For this purpose, the vacancy-binding behaviour of selected trace elements - in a first stage for unalloyed pure aluminium - will be examined by positron annihilation spectroscopy (PAS) while X-ray absorption spectroscopy (XAFS) reveals for the very early stages of decomposition the short-range order near copper atoms and atoms of trace elements. The spatial distribution of trace elements in aluminium will be investigated by electron probe micro analysis (EPMA) to estimate the respective maximum solubility in aluminium solid solution. Precipitates forming and growing during aging are examined in more detail in order to determine the total precipitation sequence of the Al-Cu-X alloy. Small-angle X-ray scattering (SAXS) will be employed as a particularly effective method for the quantitative description of the precipitation kinetics (coarsening) in the nanometer range. Since size and volume fraction of precipitates are responsible for the strength / hardness of the alloys, observing simultaneously the hardness development during natural and artificial aging contributes significantly to the understanding of the influence of trace elements on the age hardening. Based on the knowledge obtained on the role of trace elements during nucleation and growth of precipitates, we expect an important contribution to improve existing and to the development of new age-hardened wrought and cast aluminium alloys. Additionally, a significantly enhanced understanding of trace elements lead to a much better usability of secondary aluminium in recycling processes.

基于ALCU的合金具有重要的应用，作为机身的高强度轻质材料（Alcumg，Alculi），以及用于运输部门的发动机块的铸造合金（ALSICU）。但是，在这些合金中添加痕量元件可以显着提高其强度，而核定的基本原子机制到目前为止仅在表面上才能理解。基于铝的材料中的强度（增生）基于铝合金热处理期间或之后的空位扩散对照形成沉淀的形成。因此，痕量元件的高空位结合能对降水过程具有决定性的影响。在这个项目中，我们将研究痕量元素（例如<0.1 at Sn，sb，pb，bi）对成核的影响，从而对年龄增长行为的影响。来自纯元素的基于ALCU的合金的强度。该项目的目的 - 涉及痕量元素 - 是要理解其空置结合现象的基本方面，这是其浓度和铝合金中的结合强度的函数。为了揭示与热处理的合金和痕量元素之间的复杂相互作用，我们将采用几种包括仿真工具在内的互补方法。为此，将通过正电子歼灭光谱（PAS）检查选定的痕量元素的空置结合行为 - 在非合成的纯净铝的第一阶段，而X射线吸收光谱（XAFS）则揭示了分解非常早期的阶段铜原子和微量元素原子附近的短距离顺序。铝制痕量元件的空间分布将通过电子探针微分析（EPMA）研究，以估计铝固体溶液中各自的最大溶解度。更详细地检查了衰老过程中形成和生长的沉淀物，以确定al-Cu-X合金的总降水序列。小角度的X射线散射（SAX）将被用作纳米范围内沉淀动力学（粗大）定量描述的一种特别有效的方法。由于沉淀物的尺寸和体积分数是合金的强度 /硬度的原因，因此同时观察自然和人工衰老过程中的硬度发育有助于理解痕量元素对年龄硬化的影响。基于对痕量元素在沉淀物的成核和生长过程中的作用的知识，我们期望提高现有年龄固定的锻造和铸造铝合金的重要贡献。此外，对痕量元件的明显增强的理解会导致回收过程中二级铝的可用性更好。