Study on deformation mechanism of aluminum alloys containing the second-phase particles via crystal plasticity simulation

Abstract

Hard second-phase particles (SPPs) are ubiquitously present in aluminum alloys. However, in numerical simulations of their forming processes, these alloys are often treated as ideal homogeneous materials, which can lead to significant calculation errors. To address this issue, a three-dimensional (3D) mesoscopic crystal plasticity finite element (CPFE) model is developed for the 2219 aluminum alloy. This model takes into account the heterogeneity arising from different grain orientations and the presence of SPPs. The CPFE calculations are carried out by using the Abaqus software with a user material subroutine (UMAT). Additionally, the grain morphology and orientation obtained from experimental results are discretized and incorporated into the CPFE model. The consistency between the stress-strain curves and texture evolutions predicted by the CPFE model and those obtained from experimental tests validates the reliability of the model. Moreover, a comparison between the results of the CPFE model and those of the traditionally used Macro-FE model highlights the necessity of the CPFE model. Furthermore, based on the CPFE model, a comprehensive study is conducted on the influence of various factors on the deformation mechanism of the alloy. These factors include the loading direction, deformation mode, initial texture of the matrix aluminum, and the size, density, morphology of the SPPs. The results reveal that both grain orientation and the SPPs significantly enhance the inhomogeneity of the alloy's stress and strain distributions during deformation. Under the same deformation degree (5%), the relative standard deviation (RSD) of stress and strain calculated by the CPFE model with SPPs is 17.4% and 15.6% separately higher than that calculated by the homogeneous Macro-FE model. The deformation mode, loading direction, initial matrix texture, particle size and density, as well as particle morphology, all have pronounced effects on the deformation behavior of the alloys. In addition, the presence of SPPs causes a substantial change in the stress state of the matrix material. For instance, during uniaxial tension, stress triaxiality in the matrix aluminum in front of, above, behind, and below the circular SPP is separately 0.65, 0, 0.73, 0.35, which deviates significantly from the theoretical value of 0.33. Thus, the SPPs can also remarkably alter the stress state of the surrounding matrix material, potentially changing the alloy's failure mechanism. In order to conduct precise numerical simulations of the plastic forming processes for these alloys, it is necessary to take the impact of the SPPs on their deformation behavior into account.