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J. Eng. Mater. Technol. 2017;140(2):021001-021001-18. doi:10.1115/1.4037658.

Micro-computed tomography (CT) was used as a tool to investigate the deformation behavior of particulate-filled composite materials. Three different shapes of glass fillers (spherical, flake, and fiber) and filler mass fractions (5%, 10%, and 15%) were introduced to the epoxy resin. Rockwell hardness H scale indentation test was used to deform the composite material. The composite materials were scanned before and after the indentation test by using micro-CT. Displacement field for each filler type and mass fraction were measured through correlation of before and after scan data. The effects of filler type and mass fraction on the internal displacement field were investigated. It was also demonstrated that micro-CT can be used as a tool to create realistic representative volume elements (RVEs) for particulate-filled composite materials instead of randomly distributed particles within the matrix material.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 2017;140(2):021002-021002-11. doi:10.1115/1.4037659.

The authors simulated the industrially used continuous annealing conditions to process dual phase (DP) steels by using a custom designed annealing simulator. Sixty-seven percentage of cold rolled steel sheets was subjected to different processing routes, including the conventional continuous annealing line (CAL), intercritical annealing (ICA), and thermal cycling (TC), to investigate the effect of change in volume fraction, shape, and spatial distribution of martensite on tensile deformation characteristics of DP steels. Annealing parameters were derived using commercial software, including thermo-calc, jmat-pro, and dictra. Through selection of appropriate process parameters, the authors found out possibilities of significantly altering the volume fraction, morphology, and grain size distribution of martensite phase. These constituent variations showed a strong influence on tensile properties of DP steels. It was observed that TC route modified the martensite morphology from the typical lath type to in-grain globular/oblong type and significantly reduced the martensite grain size. This route improved the strength–ductility combination from 590 MPa–33% (obtained through CAL route) to 660 MPa–30%. Finally, the underlying mechanisms of crack initiation/void formation, etc., in different DP microstructures were discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 2017;140(2):021003-021003-8. doi:10.1115/1.4037660.

Grain size control of any engineering metal is very important in the hot upsetting process. Generally, the grain size directly controls the mechanical properties and performance of the material. Al–B4C composite finds extensive applications in nuclear industries, defense, and electronic industries. Therefore, the aim of this work is to study the dynamic recrystallization (DRX) behavior of Al–4 wt % B4C composite during the hot upsetting test. Experimental work was performed on sintered Al–4 wt % B4C preforms at various initial relative density (IRD) values of 80%, 85%, and 90%, and over the temperature range of 300–500 °C and strain rates range of 0.1–0.3 s−1. The DRXed grain size of Al–4 wt % B4C preforms for IRDes, and temperatures and strain rates were evaluated by using an optical microscope. The activation energy (Q) and Zener–Hollomon parameter of sintered Al–4 wt % B4C preforms were calculated for various deformation conditions and IRDes. The mathematical models of DRX were developed as a function of Zener–Hollomon parameter for various IRDes to predict the DRXed grain size. It was found that the DRXed grain size decreases with increasing Zener–Hollomon parameter. Verification tests were done between the measured and predicted DRXed grain size for various IRDes, and absolute and mean absolute error was found to be 9.92% and 8.58%, respectively.

Commentary by Dr. Valentin Fuster

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