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Experiments and modeling to characterize microstructure and hardness in 304L

Metallography, Microstructure and Analysis

Deibler, Lisa A.; Brown, Arthur B.; Puskar, J.D.

Drawn 304L stainless steel tubing was subjected to 42 different annealing heat treatments with the goal of initializing a microstructural model to select a heat treatment to soften the tubing from a hardness of 305 Knoop to 225–275 Knoop. The amount of recrystallization and grain size caused by 18 heat treatments were analyzed via optical microscopy and image analysis, revealing the full range of recrystallization from 0 to 100%. The formation of carbides during the longer duration and higher-temperature heat treatments was monitored via transmission electron microscope evaluation. The experimental results informed a model which includes recovery, recrystallization, and grain growth to predict microstructure and hardness. After initialization of the model, it was able to predict hardness with a R2 value of 0.95 and recrystallization with an R2 value of 0.99. As a result, the model was then utilized in the design and testing of a heat treatment to soften the tubing.

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TYPE Journal Article YEAR 2017
DOIOSTI

Investigation of grain-scale microstructural variability in tantalum using crystal plasticity-finite element simulations

Computational Materials Science

Lim, Hojun L.; Dingreville, Remi P.; Deibler, Lisa A.; Buchheit, Thomas E.; Battaile, Corbett C.

In this work, a crystal plasticity-finite element (CP-FE) model is used to investigate the effects of microstructural variability at a notch tip in tantalum single crystals and polycrystals. It is shown that at the macroscopic scale, the mechanical response of single crystals is sensitive to the crystallographic orientation while the response of polycrystals shows relatively small susceptibility to it. However, at the microscopic scale, the local stress and strain fields in the vicinity of the crack tip are completely determined by the local crystallographic orientation at the crack tip for both single and polycrystalline specimens with similar mechanical field distributions. Variability in the local metrics used (maximum von Mises stress and equivalent plastic strain at 3% deformation) for 100 different realizations of polycrystals fluctuates by up to a factor of 2-7 depending on the local crystallographic texture. Comparison with experimental data shows that the CP model captures variability in stress-strain response of polycrystals that can be attributed to the grain-scale microstructural variability. This work provides a convenient approach to investigate fluctuations in the mechanical behavior of polycrystalline materials induced by grain morphology and crystallographic orientations.

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TYPE Journal Article YEAR 2016
DOIOSTIScopus

Process modeling and experiments for forging and welding

Conference Proceedings of the Society for Experimental Mechanics Series

Brown, Arthur B.; Deibler, Lisa A.; Beghini, Lauren L.; Kostka, Timothy D.; Antoun, Bonnie R.

We are developing the capability to track material changes through numerous possible steps of the manufacturing process, such as forging, machining, and welding. In this work, experimental and modeling results are presented for a multiple-step process in which an ingot of stainless steel 304L is forged at high temperature, then machined into a thin slice, and finally subjected to an autogenous GTA weld. The predictions of temperature, yield stress, and recrystallized volume fraction are compared to experimental results.

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TYPE Conference Poster YEAR 2016
OSTIScopus
Results 26–50 of 68
Results 26–50 of 68