Reduction of Annealing Times for Energy Conservation in Aluminum

Carnegie Mellon University was teamed with the Alcoa Technical Center with support from the US Dept. of Energy (Office of Industrial Technology) and the Pennsylvania Technology Investment Authority (PTIA) to make processing of aluminum less costly and more energy efficient. Researchers in the Department of Materials Science and Engineering have investigated how annealing processes in the early stages of aluminum processing affect the structure and properties of the material. Annealing at high temperatures consumes significant amounts of time and energy. By making detailed measurements of the crystallography and morphology of internal structural changes they have generated new information that will provide a scientific basis for shortening processing times and consuming less energy during annealing

Efficient fast Fourier transform-based numerical implementation to simulate large strain behavior of polycrystalline materials

The final publication is available at Elsevier via https://doi.org/10.1016/j.ijplas.2017.07.001 © 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this paper, a new full-field numerical framework is proposed to model large strain phenomena in polycrystals. The proposed framework is based on the elasto-viscoplastic (EVP) fast Fourier transform (FFT) formulation presented by Lebensohn et al. (2012) and the rate dependent crystal plasticity framework developed by Asaro and Needleman (1985). In this implementation, the full-field solutions of micromechanical fields are computed on a regular, voxelized representative volume element (RVE) in which either a single or multiple grid points represent a single grain. The Asaro and Needleman (1985) formulation coupled with a semi-explicit, forward gradient time-integration scheme (Peirce et al., 1983) is used to compute local stresses and the FFT-based method is used to find local strain fluctuations at each grid point. The proposed model is calibrated using experimental uniaxial tensile test results of aluminum alloy (AA) 5754 sheet and then used to predict texture evolution and stress-strain response for balanced biaxial tension and plane-strain tension along rolling (RD) and transverse (TD) directions. The predicted stress-strain and texture results show a good agreement with experimental measurements. The CPU time required by the proposed model is compared with the original EVP-FFT model for two separate cases and the proposed model showed significant improvement in computation time (approximately 100 times faster).Natural Sciences and Engineering Research Council of Canada (NSERC) || 441668-1

A new crystal plasticity framework to simulate the large strain behaviour of aluminum alloys at warm temperatures

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.msea.2018.04.020 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/To improve metal formability, high temperature forming has become a desired manufacturing process. Phenomenological plasticity models are widely used in this application, however lack good predictive capability concerning microstructure evolution during forming. Many crystal plasticity hardening models have been developed to predict deformation phenomena of metals during high temperature forming; however, few have thermodynamic self-hardening formulations based on deformation mechanisms. This work presents a crystal plasticity based analysis with a Taylor polycrystal averaging scheme of warm forming employing a new microstructure and dislocation based strain hardening model to simulate deformation behaviour. The hardening model is derived from energy balance between dislocation storage, dislocation accumulation, and dislocation recovery, based on remobilization of immobile dislocations, due to thermal activation. The constitutive formulation is extended to include alloying effects due to solute strengthening of Mg. The material hardening properties of AA5754 are characterized for a range of temperatures at constant strain-rates. A formulation for the kinematics of dynamic strain aging is presented and employed for room-temperature simulations. The hardening characterization is then used to predict stress-strain behaviour of AA5182 for similar conditions. The model shows excellent predictability of experimental results. An analysis on the microstructural connection between temperature and stress-strain response is presented.Canada (NSERC) [no. APCPJ 441668-12]General Motors of Canad