Metals and alloys form one of the most important classes of engineering materials that affect various industries such as energy production and distribution, transportation, civil infrastructure, and national defense. In view of the large role these industries play in the economy, there is a great need in the scientific and engineering community for improving the efficiency and reliability of structural and material design. This requires the development of robust predictive models of the mechanical deformation and failure behavior of these materials that can be used in conjunction with quantitative methods of structural and material design, and safety and reliability assessment. The proposed effort will delve into material characterization and modeling through the combined use of quantitative microscopy and numerical simulation techniques. The research will leverage on recently developed experimental tools for characterization of material behavior at multiple length scales and combine them with computational models to advance greatly our ability to predict mechanical deformation and failure in materials used in engineering applications. This research will also influence education and human resource development in the STEM areas through the involvement of students; one graduate student will work towards a doctoral degree while one or two undergraduate students will be introduced to materials research as part of the program.
The proposed research will integrate quantitative multiscale experimental characterization of deformation and damage in metallic materials with modeling and simulation. The main hypothesis of the proposed investigation is the following: deformation in polycrystalline materials occurs through heterogeneous deformation (discrete slip) at the subgrain scale; we postulate that the persisting (and evolving) heterogeneities - i.e., the fluctuations in the deformation rather than the mean-field deformation - dictate the deformation and particularly failure of these materials. Hence, the research effort is aimed at developing a mechanistic understanding of deformation and failure coupled with quantitative measurements on the one hand, and developing microstructurally motivated models on the other hand. The main tasks of the research project are as follows: (i) to perform in situ SEM experiments on selected metallic materials and alloys to identify, understand, and quantify the deformation and failure mechanisms. (ii) to develop/calibrate macroscale phenomenological as well as mechanistic models based on continuum plasticity, representative volume models, and discrete dislocation dynamics based heterogeneous models. Towards this end, the behavior of two pure metals (copper and tantalum) and two engineering alloys (Al 5083, Ti6Al4V) will be investigated.
