Molecular dynamics simulations of multiphase Al-Cu and Al-Cu-Mg alloys: Strengthening phases and laser irradiation

多相Al-Cu和Al-Cu-Mg合金的分子动力学模拟：强化相和激光辐照含有析出相的合金由于其高强度而被用于许多应用中。铝基Al-Cu和Al-Cu-Mg合金在轻质结构和航空技术中特别受欢迎。这些合金的热老化导致复杂的二元和三元相的沉淀，其形成取决于温度、老化时间和合金元素的浓度。这些析出相有效地阻碍了位错的运动，从而提高了合金的强度。通过激光照射可以进一步改善机械性能，激光照射可以导致相变或位错的产生。其结果是，强度可以进一步提高，疲劳裂纹的扩展可以被延迟。在这个项目中，进行分子动力学模拟，以深入了解改善材料性能的潜在机制。为此，开发了Al-Cu-Mg相互作用势，该势考虑了激光加工模拟中推荐的电子温度依赖性。模拟的重点是位错与复杂的沉淀物的相互作用，从激光照射产生的影响的调查，和改进的沉淀物相的建模，使用Monte Carlo /分子动力学混合模拟。目的是了解不同因素，如沉淀物的晶体结构，相干应变或强度和激光照射的脉冲持续时间对强度的影响。旨在确定沉淀强化在Al-Cu和Al-Cu-Mg合金中的主要贡献。激光辐照非均匀材料时，吸收参数、电子参数和耦合参数都与位置有关。此外，在本项目中开发的电子温度相关的潜力被应用在模拟。考虑到这些依赖关系，需要进一步开发分子动力学软件IMD。此外，在IMD中的Monte Carlo分子动力学混合模拟的实施将被扩展，以模拟更真实的沉淀物的空位辅助形成。

Molecular dynamics simulations of multiphase Al-Cu and Al-Cu-Mg alloys: Strengthening phases and laser irradiation Alloys containing precipitates are used in many applications because of their high strength. Aluminium based Al-Cu and Al-Cu-Mg alloys are particularly popular in lightweight construction and aviation technology. Thermal aging of these alloys leads to precipitation of complex binary and ternary phases which form depending on temperature, aging time and concentrations of alloying elements. The strength of the alloy increases because these precipitates hinder dislocation motion effectively. Further improvement of the mechanical properties can be achieved by laser irradiation which can lead to phase transformations or generation of dislocations. As a result the strength can increase further and the propagation of fatigue cracks can be retarded. In this project molecular dynamics simulations are performed in order to gain insight into the underlying mechanisms of the improved material properties. For this purpose an interaction potential for Al-Cu-Mg is developed which takes into account electron temperature dependency as recommended for simulations of laser machining. The simulations focus on interactions of dislocations with complex precipitates, the investigation of effects resulting from laser irradiation, and improved modelling of precipitate phases using Monte Carlo / molecular dynamics hybrid simulations. The aim is to understand the influences of different factors as crystal structure of the precipitate, coherency strain or intensity and pulse duration of laser irradiation on the strength. It is intended to identify the main contributions of precipitation strengthening in Al-Cu and Al-Cu-Mg alloys. The absorption as well as electron and coupling parameters are positiondependent for laserirradiation of inhomogeneous materials. Furthermore, electron temperature dependent potentials developed in this project are applied in the simulations. Considering these dependencies requires substantial further development of the molecular dynamics software IMD. Furthermore, the implementation of the Monte Carlo molecular dynamics hybrid simulation in IMD will be extended in order to simulate the vacancy assisted formation of more realistic precipitates.