The yielding, plastic flow and fracture of age hardenable aluminium alloys depend on the quench rate to room temperature after the solution heat-treatment at elevated temperature and before the artificial ageing. We investigate three AlMgSi alloys with different grain structure and crystallographic texture experimentally to determine the effects of quench rate (either water-quenching or air-cooling) on the precipitate microstructure and the mechanical properties, i.e., yield stress, work hardening and ductility. Tensile tests on smooth and V-notch specimens and Kahn tear tests are performed to study the influence of stress state on plastic flow and fracture. In addition, finite element simulations of the mechanical tests are performed for one of the alloys to investigate the validity of an extension of the Gurson model to high-exponent anisotropic plasticity. Transmission electron microscopy investigations show that the alloys and their precipitation microstructure are differently affected by the quench rate. Common for the three alloys is that the precipitate free zones around dispersoids and grain boundaries become larger, and the yield strength of the alloys becomes lower, after air-cooling than after water-quenching. The nanostructure model NaMo was modified to account for precipitate free zones, and was able to predict both the precipitation parameters and the tensile yield strength of all tempers and materials with a reasonable degree of accuracy, except in one case. In this case, the inhomogeneous precipitation in the material is too complex to be captured by the inherent precipitation model in NaMo. Due to the lower yield strength and higher work-hardening rate after air-cooling, the failure strain is increased for the smooth and V-notch tensile tests. The crack propagation energy, calculated from the Kahn tear tests, is markedly affected by the quench rate and the effect is different depending on the grain structure and plastic anisotropy, caused by the crystallographic texture. The anisotropic porous plasticity model used in the finite element simulations is able to precisely capture the fracture initiation in all the specimen geometries of the considered alloy, whereas the crack propagation energies of the Kahn tear tests are slightly overestimated.

时效硬化铝合金的屈服，塑性流动和断裂取决于在高温下固溶热处理之后和人工时效之前的室温淬火速率。我们通过实验研究了三种具有不同晶粒结构和晶体织构的AlMgSi合金，以确定淬火速率（水淬或空冷）对析出物微观结构和力学性能（即屈服应力，加工硬化和延展性）的影响。进行光滑和V型缺口试样的拉伸试验以及Kahn撕裂试验，以研究应力状态对塑性流动和断裂的影响。此外，对一种合金进行了力学测试的有限元模拟，以研究将Gurson模型扩展到高指数各向异性塑性的有效性。透射电子显微镜研究表明，淬火速率对合金及其沉淀微观结构的影响不同。这三种合金的共同点是，空冷后与水淬后相比，弥散体和晶界周围的无沉淀区变大，合金的屈服强度变低。修改了NaMo纳米结构模型以解决无沉淀区的问题，除了一种情况外，它能够以合理的准确度预测所有回火和材料的沉淀参数和拉伸屈服强度。在这种情况下，材料中的不均匀沉淀太复杂，无法用NaMo中的固有沉淀模型捕获。由于空冷后屈服强度较低，加工硬化率较高，因此在平滑和V型缺口拉伸试验中，破坏应变会增加。根据卡恩撕裂试验计算出的裂纹扩展能量受淬火速度的影响很大，其影响因晶体组织和晶粒结构和塑性各向异性而异。有限元模拟中使用的各向异性多孔塑性模型能够精确地捕获所考虑合金的所有试样几何形状中的断裂起点，而卡恩撕裂试验的裂纹扩展能却被高估了一点。