Metals

Research

Jump to: Review

10 pages, 4083 KiB

Open AccessArticle

Kinetics of HCP-BCC Phase Transition Boundary in Magnesium at High Pressure

by Nitin P. Daphalapurkar

Metals 2024, 14(6), 609; https://doi.org/10.3390/met14060609 - 22 May 2024

Viewed by 507

Abstract

Under high pressures, many crystalline metals undergo solid–solid phase transformations. In order to accurately model the behavior of materials under extreme loading conditions, it is essential to understand the kinetics of phase transition. Using molecular dynamics simulations, this work demonstrates the feasibility of [...] Read more.

Under high pressures, many crystalline metals undergo solid–solid phase transformations. In order to accurately model the behavior of materials under extreme loading conditions, it is essential to understand the kinetics of phase transition. Using molecular dynamics simulations, this work demonstrates the feasibility of characterizing the speeds of a moving phase boundary using atomistic simulations employing a suitable empirical potential for single-crystal magnesium. The model can provide temperature- and tensorial stress-dependent velocity of a moving phase boundary as a rate-limiting contribution to the kinetics of phase transformation in continuum codes. Results demonstrate that a nonlinear interaction exists between plasticity and phase transition, facilitating a jump in the velocity of a moving phase boundary, facilitated by activated plastic deformation mechanisms. Full article

(This article belongs to the Special Issue Dynamic Response of Metals under Extreme Conditions)

► Show Figures

Figure 1

17 pages, 30600 KiB

Open AccessArticle

Spall Failure of ECAE Mg-Al Alloys at Extreme Strain Rates: Influence of a Refined Precipitate and Grain Microstructure

by Christopher S. DiMarco, Peter Lim, Debjoy Mallick, Laszlo Kecskes, Timothy P. Weihs and K. T. Ramesh

Metals 2023, 13(3), 454; https://doi.org/10.3390/met13030454 - 22 Feb 2023

Cited by 2 | Viewed by 1500

Abstract

The development of advanced materials for extreme dynamic environments requires an understanding of the links between the microstructure and the response of the material (i.e., Materials-by-Design). Spall failure significantly limits material performance at high strain rates, but our understanding of the influence of [...] Read more.

The development of advanced materials for extreme dynamic environments requires an understanding of the links between the microstructure and the response of the material (i.e., Materials-by-Design). Spall failure significantly limits material performance at high strain rates, but our understanding of the influence of microstructure on spall strength is limited. While models suggest that increasing the static yield strength by adding precipitates or refining grain size can improve the spall strength, it is possible that the associated increase in nucleation sites may have deleterious effects on spall performance. Herein, we examine spall failure of a Magnesium-Aluminum system with precipitation and grain size strengthening through novel high-throughput laser-driven micro-flyer (LDMF) impact experiments. Six microstructures are investigated, four with grain sizes around 2–3 μm and precipitates around 0.5–1 μm, and two that are precipitate-free with grain sizes around 500 μm at six and nine percent Aluminum contents. The LDMF method allows us to detect differences in spall strength with relatively small changes in microstructure. The spall strength is observed to be strongly affected by varying levels of precipitates and consistently shows a notable reduction in average spall strength around 8–19% with the addition of precipitates, with values ranging from 1.22–1.50 GPa. The spall strength is also seen to decrease with the refinement of grain size independent of composition. However, this decrease is small compared to the hundred-fold grain size reduction. While ductile void growth is observed across all samples, greater variability and a further decrease in strength are seen with an increasing numbers of non-uniformly dispersed precipitates. Full article

(This article belongs to the Special Issue Dynamic Response of Metals under Extreme Conditions)

► Show Figures

Figure 1

17 pages, 5849 KiB

Open AccessFeature PaperArticle

The Challenges of Modeling Defect Behavior and Plasticity across Spatial and Temporal Scales: A Case Study of Metal Bilayer Impact

by Leah Granger, Muh-Jang Chen, Donald Brenner and Mohammed Zikry

Metals 2022, 12(12), 2036; https://doi.org/10.3390/met12122036 - 26 Nov 2022

Cited by 2 | Viewed by 1112

Abstract

Atomistic molecular dynamics (MD) and a microstructural dislocation density-based crystalline plasticity (DCP) framework were used together across time scales varying from picoseconds to nanoseconds and length scales spanning from angstroms to micrometers to model a buried copper–nickel interface subjected to high strain rates. [...] Read more.

Atomistic molecular dynamics (MD) and a microstructural dislocation density-based crystalline plasticity (DCP) framework were used together across time scales varying from picoseconds to nanoseconds and length scales spanning from angstroms to micrometers to model a buried copper–nickel interface subjected to high strain rates. The nucleation and evolution of defects, such as dislocations and stacking faults, as well as large inelastic strain accumulations and wave-induced stress reflections were physically represented in both approaches. Both methods showed similar qualitative behavior, such as defects originating along the impactor edges, a dominance of Shockley partial dislocations, and non-continuous dislocation distributions across the buried interface. The favorable comparison between methods justifies assumptions used in both, to model phenomena, such as the nucleation and interactions of single defects and partials with reflected tensile waves, based on MD predictions, which are consistent with the evolution of perfect and partial dislocation densities as predicted by DCP. This substantiates how the nanoscale as modeled by MD is representative of microstructural behavior as modeled by DCP. Full article

(This article belongs to the Special Issue Dynamic Response of Metals under Extreme Conditions)

► Show Figures

Figure 1

17 pages, 2924 KiB

Open AccessArticle

A Multi-Phase Modeling Framework Suitable for Dynamic Applications

by Nathan R. Barton, Darby J. Luscher, Corbett Battaile, Justin L. Brown, Miles Buechler, Leonid Burakovsky, Scott Crockett, Carl Greeff, Ann E. Mattsson, Michael B. Prime and William J. Schill

Metals 2022, 12(11), 1844; https://doi.org/10.3390/met12111844 - 28 Oct 2022

Cited by 2 | Viewed by 1412

Abstract

Under dynamic loading conditions and the associated extreme conditions many metals will undergo phase transformations. The change in crystal structure associated with solid–solid phase transformations can significantly alter the subsequent mechanical response of the material. For the interpretation of experiments involving dynamic loading [...] Read more.

Under dynamic loading conditions and the associated extreme conditions many metals will undergo phase transformations. The change in crystal structure associated with solid–solid phase transformations can significantly alter the subsequent mechanical response of the material. For the interpretation of experiments involving dynamic loading it is beneficial to have a modeling framework that captures key features of the material response while remaining relatively simple. We introduce a candidate framework and apply it to the metal tin to highlight a range of behaviors that are captured by the model. We also discuss potential extensions to capture additional behaviors that could be important for certain materials and loading scenarios. The model is useful for analysis of results from dynamic experiments and offers a point of departure for more complex model formulations. Full article

(This article belongs to the Special Issue Dynamic Response of Metals under Extreme Conditions)

► Show Figures

Figure 1

11 pages, 1916 KiB

Open AccessArticle

Miniature Beryllium Split-Hopkinson Pressure Bars for Extending the Range of Achievable Strain-Rates

by Bryan Zuanetti, Kyle J. Ramos, Carl M. Cady, Chris S. Meredith, Daniel T. Casem, Adam Golder and Cynthia A. Bolme

Metals 2022, 12(11), 1834; https://doi.org/10.3390/met12111834 - 28 Oct 2022

Cited by 2 | Viewed by 1343

Abstract

Conventional Split Hopkinson Pressure Bars (SHPB) or “Kolsky” bars are often used for determining the high-rate compressive yield and failure strength of materials. However, for experiments generating very high strain-rates (>10³/s) miniaturization of the setup is often required for minimizing the [...] Read more.

Conventional Split Hopkinson Pressure Bars (SHPB) or “Kolsky” bars are often used for determining the high-rate compressive yield and failure strength of materials. However, for experiments generating very high strain-rates (>10³/s) miniaturization of the setup is often required for minimizing the effects of elastic wave dispersion in order to enable the inference of decreasingly short loading events from the data. Miniature aluminum and steel bars are often sufficient for meeting these requirements. However, for high enough strain-rates, miniaturization of steel or aluminum Kolsky bars may require prohibitively small diameter bars and test specimens that could become inappropriate for inferring representative properties of materials with large grain size relative to the test specimen size. The use of a beryllium Kolsky bar setup is expected to enable high rates to be accessible with larger diameter bars/specimen combinations due to the inherent physical properties of beryllium, which are expected to minimize the effects of elastic wave dispersion. For this reason, a series of beryllium Kolsky bars have been developed, and, in this paper, the dispersion characteristics of these bars are measured and compare the data with those of similarly sized 7075-T6 aluminum and C350 maraging steel. The results, which agree well with the theory, show no appreciable frequency dependence of the elastic wavespeed in the data from the beryllium bars, demonstrating its advantage over aluminum and steel in application to Kolsky bars. Full article

(This article belongs to the Special Issue Dynamic Response of Metals under Extreme Conditions)

► Show Figures

Figure 1

14 pages, 5183 KiB

Open AccessArticle

Shock Hugoniot of Forged and Additively Manufactured 304L Stainless Steel

by Sarah A. Thomas, Michelle C. Hawkins, Robert S. Hixson, Ramon M. Martinez, George T. Gray III, Darby J. Luscher and Saryu J. Fensin

Metals 2022, 12(10), 1661; https://doi.org/10.3390/met12101661 - 2 Oct 2022

Cited by 4 | Viewed by 1417

Abstract

The purpose of this research was to measure the equation of state for additively manufactured (AM) and forged 304L stainless steel using a novel experimental technique. An understanding of the dynamic behavior of AM metals is integral to their timely adoption into various [...] Read more.

The purpose of this research was to measure the equation of state for additively manufactured (AM) and forged 304L stainless steel using a novel experimental technique. An understanding of the dynamic behavior of AM metals is integral to their timely adoption into various applications. The Hugoniot of the AM 304L was compared to that of the forged 304L at particle velocities where the material retains a two-wave structure. This comparison enabled us to determine the sensitivity of the equation of state to microstructure as varied due to processing. Our results showed that there was a measurable difference in the measured shock velocity between the AM and forged 304L. The shock wave velocities for the AM 304L were found to be ~3% slower than those for the forged 304L at similar particle velocities. To understand these differences, properties such as densities, sound speeds, and texture were measured and compared between the forged and AM materials. Our results showed that no measurable difference was found in these properties. Additionally, it is possible that differing elastic wave amplitudes may influence shock velocity Full article

(This article belongs to the Special Issue Dynamic Response of Metals under Extreme Conditions)

► Show Figures

Figure 1

13 pages, 6667 KiB

Open AccessArticle

Effect of Grain Boundary Misorientation on Spall Strength in Ta via Shock-Free Simulations with Relatively Few Atoms

by Jo Caulkins, Carlisle Fauver, Sara Adibi and Justin Wilkerson

Metals 2022, 12(10), 1586; https://doi.org/10.3390/met12101586 - 23 Sep 2022

Viewed by 1455

Abstract

A suite of 37 molecular dynamics simulations is conducted at two system sizes to systematically characterize the role of grain boundary (GB) misorientation on spall strength in pure BCC tantalum (Ta). The systems studied consist of bicrystals with a single [110] symmetric tilt [...] Read more.

A suite of 37 molecular dynamics simulations is conducted at two system sizes to systematically characterize the role of grain boundary (GB) misorientation on spall strength in pure BCC tantalum (Ta). The systems studied consist of bicrystals with a single [110] symmetric tilt grain boundary. Two loading conditions are compared: (i) homogeneous extension under uniaxial strain simulated in this study and (ii) piston/flyer impact of sample, which induces heterogeneous deformation via shockwave propagation along the length of the sample. The piston/flyer impact is taken from the literature and run on the same set of GB misorientation angles using LAMMPS. The major finding here is that both methods result in similar spall strength predictions, but the homogeneous extension method generally requires two to three orders of magnitude fewer atoms and similar reductions in computational costs. Spall strength results systematically overpredict using this method, by about 10% for the dataset three orders of magnitude smaller than piston/flyer simulations, and 5% for the dataset two orders of magnitude smaller. Lastly, the effect of system size and pre-compression magnitude on spall strength is systematically characterized. Full article

(This article belongs to the Special Issue Dynamic Response of Metals under Extreme Conditions)

► Show Figures

Figure 1

12 pages, 2933 KiB

Open AccessArticle

High-Strain Rate Spall Strength Measurement for CoCrFeMnNi High-Entropy Alloy

by Andrew Ehler, Abhijeet Dhiman, Tyler Dillard, Remi Dingreville, Erin Barrick, Andrew Kustas and Vikas Tomar

Metals 2022, 12(9), 1482; https://doi.org/10.3390/met12091482 - 7 Sep 2022

Cited by 5 | Viewed by 2130

Abstract

In this study, we experimentally investigate the high stain rate and spall behavior of Cantor high-entropy alloy (HEA), CoCrFeMnNi. First, the Hugoniot equations of state (EOS) for the samples are determined using laser-driven CoCrFeMnNi flyers launched into known Lithium Fluoride (LiF) windows. Photon [...] Read more.

In this study, we experimentally investigate the high stain rate and spall behavior of Cantor high-entropy alloy (HEA), CoCrFeMnNi. First, the Hugoniot equations of state (EOS) for the samples are determined using laser-driven CoCrFeMnNi flyers launched into known Lithium Fluoride (LiF) windows. Photon Doppler Velocimetry (PDV) recordings of the velocity profiles find the EOS coefficients using an impedance mismatch technique. Following this set of measurements, laser-driven aluminum flyer plates are accelerated to velocities of 0.5–1.0 km/s using a high-energy pulse laser. Upon impact with CoCrFeMnNi samples, the shock response is found through PDV measurements of the free surface velocities. From this second set of measurements, the spall strength of the alloy is found for pressures up to 5 GPa and strain rates in excess of 10⁶ s⁻¹. Further analysis of the failure mechanisms behind the spallation is conducted using fractography revealing the occurrence of ductile fracture at voids presumed to be caused by chromium oxide deposits created during the manufacturing process. Full article

(This article belongs to the Special Issue Dynamic Response of Metals under Extreme Conditions)

► Show Figures

Figure 1

Review

Jump to: Research

22 pages, 67923 KiB

Open AccessReview

Void Mediated Failure at the Extremes: Spallation in Magnesium and Aluminum

by Cyril Labode Williams

Metals 2022, 12(10), 1667; https://doi.org/10.3390/met12101667 - 5 Oct 2022

Cited by 2 | Viewed by 1313

Abstract

This paper reviews the role of void nucleation, growth, and coalescence on the spall failure process in light metals. Based on the review of the open literature, the preponderance of evidence show that void nucleation, growth, and coalescence are prevalent in light metals [...] Read more.

This paper reviews the role of void nucleation, growth, and coalescence on the spall failure process in light metals. Based on the review of the open literature, the preponderance of evidence show that void nucleation, growth, and coalescence are prevalent in light metals such as HCP magnesium and FCC aluminum alloys. The as-received microstructure and its evolution play a crucial role on how voids nucleate, grow, and coalesce. Nucleation of voids in these light metals and metallic alloys can be either homogeneous and heterogeneous but at high enough stresses, both homogeneous and heterogeneous nucleation can be activated simultaneously. Secondary phase particles and intermetallics can strongly influence spall failure, through matrix-precipitate/intermetallic debonding or precipitate/intermetallic cracking during shock compression. Studying spall failure through modeling has proven to be an invaluable tool in developing a fundamental understanding of void nucleation, growth, coalescence, and consequent spall failure. However, since new alloys are currently been developed, more experimental and modeling research are needed to further understand how spall failure initiate and grow in these new alloys. Full article

(This article belongs to the Special Issue Dynamic Response of Metals under Extreme Conditions)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Dynamic Response of Metals under Extreme Conditions

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (9 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI