| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 107 === Lightweighting is an important technology trend in the automotive industry. To this end, aluminum alloys have now emerged as a strong candidate of lightweight materials for the industry. For 6000-series aluminum alloys, both microstructural controls and warm forming techniques are the key issues to be resolved in the automotive application. Crystal plasticity finite element method (CPFEM) that links slip activities with mechanical properties is a natural choice to study these issues.
The objective of this study is to incorporate proper precipitate hardening and temperature effects into CPFEM. It is well-known that in the physical-based CPFEM (or implicit model), the effect of geometrically necessary dislocation (GND) is averaged in the constitutive law. This study also extends the implicit model with different precipitate geometries (aka, explicit model) and investigate their effects on texture and mechanical behavior.
The constitutive model is implemented in Abaqus UMAT. Geometries of precipitate such as shape, size, distribution and volume fraction are considered by Dream.3D. In contrast with the implicit model, the local dislocation density, stress concentration and misorientation around precipitate can be predicted by the explicit model. Moreover, the activating slip systems are analyzed under various crystal orientations and types of precipitate.
Finally, we apply CPFEM to study surface roughening effects and texture under plane stain tensile loading. We find that texture band causes surface roughening and higher temperature increases surface roughening effect. In addition, deformation incompatibility between precipitate and crystal limit grain rotation. A 6000 series aluminum alloy, AA6016-T4P, is analyzed under tensile loading. Dislocation density accumulated around precipitate and grain boundary was successfully predicted. Grain orientations after deformation are found to be preferable in <100>//RD.
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