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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.


Related in: MedlinePlus

Selected images from a synchrotron x-ray radiography sequence of solidification in a 0.2 mm thick Al-10 at.% In section, highlighting In-rich L2 liquid phase (dark) along the solid-liquid interface and In-rich L2 channel development.In addition to the solidification progression, the corresponding video (Supplementary Information Video S2) reveals In-rich droplet motion and coarsening within the majority L1 liquid phase.
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f4: Selected images from a synchrotron x-ray radiography sequence of solidification in a 0.2 mm thick Al-10 at.% In section, highlighting In-rich L2 liquid phase (dark) along the solid-liquid interface and In-rich L2 channel development.In addition to the solidification progression, the corresponding video (Supplementary Information Video S2) reveals In-rich droplet motion and coarsening within the majority L1 liquid phase.

Mentions: Macroscopic fluid currents exist in the alloy melt, as evidenced by sedimentation during melting in Figure 2, in concert with meso- and micro-scale flows that are influenced by external fields (i.e. gravity, thermo-capillarity, or Stokes drag forces acting on second phase droplets2122). These flows affect morphological evolution during solidification. To reveal dynamic processes occurring in Al-10 at.% In during melting and solidification at smaller length scales, we performed complementary synchrotron x-ray radiography, imaging approximately a 1.4 × 1.74 mm field of view in a 0.2 mm thick section, at the Sector 32-Insertion Device beamline at Argonne National Laboratory's Advanced Photon Source. It is important to reiterate that the sample volume interrogated using x-rays is over four orders of magnitude smaller than that probed using protons at pRad. A series of images from an x-ray solidification sequence is shown in Figure 4. An accompanying video (see Supplementary Information Video S2) highlights L1/L2 fluid flow, including the formation, coarsening (ripening and coalescence), and complex collective motion of In-rich L2 droplets within the majority L1 liquid phase at elevated temperatures. In a constant but small thermal gradient, the droplet motion is highly irregular, with larger scale convective currents sweeping in and out of the field of view. Once the monotectic front approaches the field of view, more organized motion begins to dominate. During solidification, L2 droplets are on a trajectory toward the advancing solid-liquid interface (see Figure 4 and the accompanying Supplementary Information Video S2). These L2 droplets accumulate at the solid-liquid interface and are either pushed along that interface, or are engulfed in the solidifying Al matrix, creating In-rich channels (Figure 4). The same physics observed by Schaffer et al.21 in an x-ray study of the Al-Bi system apply to droplet motion in our study; however, more chaotic convection currents appear to exist in our samples during cooling. The solid-liquid interface advances at a growth velocity of approximately 145 μm/s. The x-ray images also suggest that indium wets the crucible walls in some instances, which promotes the formation of In-rich channels at these locations. Hydrodynamic effects of the L2 liquid phase exist at the micro-, meso-, and macro- length scales in this hypermonotectic alloy and substantially influence the resulting solidification structure. Improved understanding of micro- and meso-scale L2 droplet motion may provide a methodology to advantageously control alloy melt flows in these alloys to offset macro-scale sedimentation and improve casting quality2122.


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)

Selected images from a synchrotron x-ray radiography sequence of solidification in a 0.2 mm thick Al-10 at.% In section, highlighting In-rich L2 liquid phase (dark) along the solid-liquid interface and In-rich L2 channel development.In addition to the solidification progression, the corresponding video (Supplementary Information Video S2) reveals In-rich droplet motion and coarsening within the majority L1 liquid phase.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Selected images from a synchrotron x-ray radiography sequence of solidification in a 0.2 mm thick Al-10 at.% In section, highlighting In-rich L2 liquid phase (dark) along the solid-liquid interface and In-rich L2 channel development.In addition to the solidification progression, the corresponding video (Supplementary Information Video S2) reveals In-rich droplet motion and coarsening within the majority L1 liquid phase.
Mentions: Macroscopic fluid currents exist in the alloy melt, as evidenced by sedimentation during melting in Figure 2, in concert with meso- and micro-scale flows that are influenced by external fields (i.e. gravity, thermo-capillarity, or Stokes drag forces acting on second phase droplets2122). These flows affect morphological evolution during solidification. To reveal dynamic processes occurring in Al-10 at.% In during melting and solidification at smaller length scales, we performed complementary synchrotron x-ray radiography, imaging approximately a 1.4 × 1.74 mm field of view in a 0.2 mm thick section, at the Sector 32-Insertion Device beamline at Argonne National Laboratory's Advanced Photon Source. It is important to reiterate that the sample volume interrogated using x-rays is over four orders of magnitude smaller than that probed using protons at pRad. A series of images from an x-ray solidification sequence is shown in Figure 4. An accompanying video (see Supplementary Information Video S2) highlights L1/L2 fluid flow, including the formation, coarsening (ripening and coalescence), and complex collective motion of In-rich L2 droplets within the majority L1 liquid phase at elevated temperatures. In a constant but small thermal gradient, the droplet motion is highly irregular, with larger scale convective currents sweeping in and out of the field of view. Once the monotectic front approaches the field of view, more organized motion begins to dominate. During solidification, L2 droplets are on a trajectory toward the advancing solid-liquid interface (see Figure 4 and the accompanying Supplementary Information Video S2). These L2 droplets accumulate at the solid-liquid interface and are either pushed along that interface, or are engulfed in the solidifying Al matrix, creating In-rich channels (Figure 4). The same physics observed by Schaffer et al.21 in an x-ray study of the Al-Bi system apply to droplet motion in our study; however, more chaotic convection currents appear to exist in our samples during cooling. The solid-liquid interface advances at a growth velocity of approximately 145 μm/s. The x-ray images also suggest that indium wets the crucible walls in some instances, which promotes the formation of In-rich channels at these locations. Hydrodynamic effects of the L2 liquid phase exist at the micro-, meso-, and macro- length scales in this hypermonotectic alloy and substantially influence the resulting solidification structure. Improved understanding of micro- and meso-scale L2 droplet motion may provide a methodology to advantageously control alloy melt flows in these alloys to offset macro-scale sedimentation and improve casting quality2122.

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.


Related in: MedlinePlus