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：强化相和含有析出相的激光辐照合金因其高强度而被广泛应用。铝基铝铜和铝铜镁合金在轻量化建筑和航空技术中特别受欢迎。这些合金的热时效导致复杂的二元和三元相的析出，这些相的形成取决于温度、时效时间和合金元素的浓度。这些析出物有效地阻碍了位错的运动，从而提高了合金的强度。激光辐照可导致相变或位错的产生，从而进一步改善材料的力学性能。因此，可以进一步提高强度，延缓疲劳裂纹的扩展。在这个项目中，为了深入了解材料性能改善的潜在机制，进行了分子动力学模拟。为此目的，开发了Al-Cu-Mg的相互作用势，它考虑了激光加工模拟中所推荐的电子温度依赖性。模拟的重点是位错与复杂沉淀的相互作用，激光照射的影响的研究，以及使用蒙特卡罗/分子动力学混合模拟改进的沉淀相的模拟。目的是了解不同因素，如沉淀物的晶体结构、共格应变或强度以及激光照射的脉冲宽度对强度的影响。确定了Al-Cu和Al-Cu-Mg合金中析出强化的主要贡献。对于非均匀材料的激光辐照，吸收、电子和耦合参数都是位置相关的。此外，本项目中开发的电子温度依赖势被应用于模拟。考虑到这些相关性，需要对分子动力学软件IMD进行实质性的进一步开发。此外，还将扩展蒙特卡罗分子动力学混合模拟在IMD中的实现，以模拟更真实的空位辅助沉淀的形成。

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.