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Proton radiography peers into metal solidification.

Clarke A, Imhoff S, Gibbs P, Cooley J, Morris C, Merrill F, Hollander B, Mariam F, Ott T, Barker M, Tucker T, Lee WK, Fezzaa K, Deriy A, Patterson B, Clarke K, Montalvo J, Field R, Thoma D, Smith J, Teter D - Sci Rep (2013)

Bottom Line: Understanding the link between processing and structure is important because structure profoundly affects the properties of engineering materials.We also show complementary x-ray results from a small volume (<1 mm(3)), bridging four orders of magnitude.Real-time imaging will enable efficient process development and the control of structure evolution to make materials with intended properties; it will also permit the development of experimentally informed, predictive structure and process models.

View Article: PubMed Central - PubMed

Affiliation: Los Alamos National Laboratory, Los Alamos, NM 87545, USA. aclarke@lanl.gov

ABSTRACT
Historically, metals are cut up and polished to see the structure and to infer how processing influences the evolution. We can now peer into a metal during processing without destroying it using proton radiography. Understanding the link between processing and structure is important because structure profoundly affects the properties of engineering materials. Synchrotron x-ray radiography has enabled real-time glimpses into metal solidification. However, x-ray energies favor the examination of small volumes and low density metals. Here we use high energy proton radiography for the first time to image a large metal volume (>10,000 mm(3)) during melting and solidification. We also show complementary x-ray results from a small volume (<1 mm(3)), bridging four orders of magnitude. Real-time imaging will enable efficient process development and the control of structure evolution to make materials with intended properties; it will also permit the development of experimentally informed, predictive structure and process models.

No MeSH data available.


(a) A proton radiography image (Figure 2) of the solidification structure and (b,c) corresponding post-mortem scanning electron microscopy of the indicated regions that highlight the In-rich boundaries and regions that exist within the colonies of the solidified structure.In (a), the higher density In-rich boundaries appear dark, whereas the In-rich boundaries and regions appear bright in (b,c). The In-rich boundaries and regions in (b) and (c) contain a fine-scale Al-rich (dark) phase.
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f3: (a) A proton radiography image (Figure 2) of the solidification structure and (b,c) corresponding post-mortem scanning electron microscopy of the indicated regions that highlight the In-rich boundaries and regions that exist within the colonies of the solidified structure.In (a), the higher density In-rich boundaries appear dark, whereas the In-rich boundaries and regions appear bright in (b,c). The In-rich boundaries and regions in (b) and (c) contain a fine-scale Al-rich (dark) phase.

Mentions: Advancement of the solid-liquid interface is shown in the representative solidification sequence images. The solid-liquid interface advances at an average growth velocity of approximately 200 μm/s in the vertical direction (antiparallel to the global heat flow direction). The growth velocity actually varies somewhat from the edge to the center of the field of view due to heat extraction from the edges of the crucible, which is reflected in the interface shape. These images also highlight the monotectic reaction during solidification and reveal the spatial distribution of meso-scale monotectic colonies. The darker streaks observed in the pRad images (Figure 2) correspond to a projection through colony boundaries that contain a higher volume fraction of indium. Although we selected a 6 mm thick section for our pRad study, pRad also affords the flexibility to examine thinner, constrained sections. This might reduce potential projection issues associated with thicker sections, but if three-dimensional information is required for a particular study, proton tomography42 (like x-ray tomography2329303233) is possible. If only some three-dimensional information is desired, additional radiographs taken at select rotations would afford construction of a stereo image. Microstructural features observed during microscopic examination of ex-situ serial sections from our pRad field of view are consistent with those we observe in pRad images, suggesting that through-thickness projection is not a major concern in our study aimed at monitoring macro- and mesoscale fluid flow. An area containing representative In-rich boundaries in a pRad image is highlighted in Figure 3(a); a higher magnification post-mortem scanning electron microscopy image of that region is shown in Figure 3(b), along with an even higher magnification image in Figure 3(c). Here, the In-rich boundaries and regions within the colonies appear bright and exist in two size classes – either as high aspect ratio fibers or as low aspect ratio droplets. These regions contain a fine-scale Al-rich phase, presumably associated with solute separation as aluminum solubility in L2 decreases during cooling from the monotectic reaction (the invariant reaction at 636.5°C). The images in Figure 3 reflect the coupled complexities of structure evolution that transpired at a variety of length scales in this alloy system.


Proton radiography peers into metal solidification.

Clarke A, Imhoff S, Gibbs P, Cooley J, Morris C, Merrill F, Hollander B, Mariam F, Ott T, Barker M, Tucker T, Lee WK, Fezzaa K, Deriy A, Patterson B, Clarke K, Montalvo J, Field R, Thoma D, Smith J, Teter D - Sci Rep (2013)

(a) A proton radiography image (Figure 2) of the solidification structure and (b,c) corresponding post-mortem scanning electron microscopy of the indicated regions that highlight the In-rich boundaries and regions that exist within the colonies of the solidified structure.In (a), the higher density In-rich boundaries appear dark, whereas the In-rich boundaries and regions appear bright in (b,c). The In-rich boundaries and regions in (b) and (c) contain a fine-scale Al-rich (dark) phase.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3686777&req=5

f3: (a) A proton radiography image (Figure 2) of the solidification structure and (b,c) corresponding post-mortem scanning electron microscopy of the indicated regions that highlight the In-rich boundaries and regions that exist within the colonies of the solidified structure.In (a), the higher density In-rich boundaries appear dark, whereas the In-rich boundaries and regions appear bright in (b,c). The In-rich boundaries and regions in (b) and (c) contain a fine-scale Al-rich (dark) phase.
Mentions: Advancement of the solid-liquid interface is shown in the representative solidification sequence images. The solid-liquid interface advances at an average growth velocity of approximately 200 μm/s in the vertical direction (antiparallel to the global heat flow direction). The growth velocity actually varies somewhat from the edge to the center of the field of view due to heat extraction from the edges of the crucible, which is reflected in the interface shape. These images also highlight the monotectic reaction during solidification and reveal the spatial distribution of meso-scale monotectic colonies. The darker streaks observed in the pRad images (Figure 2) correspond to a projection through colony boundaries that contain a higher volume fraction of indium. Although we selected a 6 mm thick section for our pRad study, pRad also affords the flexibility to examine thinner, constrained sections. This might reduce potential projection issues associated with thicker sections, but if three-dimensional information is required for a particular study, proton tomography42 (like x-ray tomography2329303233) is possible. If only some three-dimensional information is desired, additional radiographs taken at select rotations would afford construction of a stereo image. Microstructural features observed during microscopic examination of ex-situ serial sections from our pRad field of view are consistent with those we observe in pRad images, suggesting that through-thickness projection is not a major concern in our study aimed at monitoring macro- and mesoscale fluid flow. An area containing representative In-rich boundaries in a pRad image is highlighted in Figure 3(a); a higher magnification post-mortem scanning electron microscopy image of that region is shown in Figure 3(b), along with an even higher magnification image in Figure 3(c). Here, the In-rich boundaries and regions within the colonies appear bright and exist in two size classes – either as high aspect ratio fibers or as low aspect ratio droplets. These regions contain a fine-scale Al-rich phase, presumably associated with solute separation as aluminum solubility in L2 decreases during cooling from the monotectic reaction (the invariant reaction at 636.5°C). The images in Figure 3 reflect the coupled complexities of structure evolution that transpired at a variety of length scales in this alloy system.

Bottom Line: Understanding the link between processing and structure is important because structure profoundly affects the properties of engineering materials.We also show complementary x-ray results from a small volume (<1 mm(3)), bridging four orders of magnitude.Real-time imaging will enable efficient process development and the control of structure evolution to make materials with intended properties; it will also permit the development of experimentally informed, predictive structure and process models.

View Article: PubMed Central - PubMed

Affiliation: Los Alamos National Laboratory, Los Alamos, NM 87545, USA. aclarke@lanl.gov

ABSTRACT
Historically, metals are cut up and polished to see the structure and to infer how processing influences the evolution. We can now peer into a metal during processing without destroying it using proton radiography. Understanding the link between processing and structure is important because structure profoundly affects the properties of engineering materials. Synchrotron x-ray radiography has enabled real-time glimpses into metal solidification. However, x-ray energies favor the examination of small volumes and low density metals. Here we use high energy proton radiography for the first time to image a large metal volume (>10,000 mm(3)) during melting and solidification. We also show complementary x-ray results from a small volume (<1 mm(3)), bridging four orders of magnitude. Real-time imaging will enable efficient process development and the control of structure evolution to make materials with intended properties; it will also permit the development of experimentally informed, predictive structure and process models.

No MeSH data available.