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.

铝基合金作为航空机身的高强度轻质材料（AlCuMg, calculus）和运输领域发动机缸体的铸造合金（AlSiCu）有着重要的应用。然而，在这些合金中加入微量元素可以显著提高它们的强度，而潜在的原子成核机制到目前为止还只是表面上的了解。铝基材料强度的增加（时效硬化）是基于在铝合金热处理过程中或热处理后析出物的真空扩散控制形成。因此，微量元素的高空位结合能对沉淀过程有决定性的影响。在这个项目中，我们将研究微量元素（如In， Sn, Sb, Pb, Bi < 0.1%）对成核的影响，从而对时效硬化行为的影响。纯元素铝基合金的强度。这个关于微量元素的项目的目的是了解它们的空位结合现象的基本方面，作为它们在铝合金中的浓度和结合强度的函数。为了揭示合金和微量元素与热处理中淬火空位之间复杂的相互作用，我们将采用几种辅助方法，包括模拟工具。为此，选定的微量元素的空位结合行为-在非合金纯铝的第一阶段-将通过正电子湮灭光谱（PAS）进行检查，而x射线吸收光谱（XAFS）揭示了在分解的非常早期阶段铜原子和微量元素原子附近的短程顺序。利用电子探针微量分析（EPMA）研究铝中微量元素的空间分布，以估计其在铝固溶体中的最大溶解度。为了确定Al-Cu-X合金的总析出顺序，对时效过程中析出相的形成和生长进行了较为详细的研究。小角度x射线散射（SAXS）将被用作纳米范围内沉淀动力学（粗化）定量描述的一种特别有效的方法。由于析出相的尺寸和体积分数与合金的强度/硬度有关，因此同时观察自然时效和人工时效过程中的硬度变化有助于理解微量元素对时效硬化的影响。基于对微量元素在析出相形核和生长过程中的作用的认识，我们期望对改进现有的和开发新的时效硬化变形铝合金和铸铝合金做出重要贡献。此外，对微量元素的理解显著增强，导致再生铝在回收过程中的可用性大大提高。