Abstract
The structural and mechanical response of metals is intimately connected to phase transformations. For instance, the product of a phase transformation (martensite) is responsible for the extraordinary range of strength and toughness of steel, making it a versatile and important structural material. Although abundant in metals and alloys, the discovery of new phase transformations is not currently a common event and often requires a mix of experimentation, predictive computations, and luck. High-energy pulsed lasers enable the exploration of extreme pressures and temperatures, where such discoveries may lie. The formation of a hexagonal (omega) phase was observed in recovered monocrystalline body-centered cubic tantalum of four crystallographic orientations subjected to an extreme regime of pressure, temperature, and strain-rate. This was accomplished using high-energy pulsed lasers. The omega phase and twinning were identified by transmission electron microscopy at 70 GPa (determined by a corresponding VISAR experiment). It is proposed that the shear stresses generated by the uniaxial strain state of shock compression play an essential role in the transformation. Molecular dynamics simulations show the transformation of small nodules from body-centered cubic to a hexagonal close-packed structure under the same stress state (pressure and shear).
Highlights
The structural and mechanical response of metals is intimately connected to phase transformations
It is proposed that the shear stresses generated by the uniaxial strain state of shock compression play an essential role in the transformation
These observations are backed by molecular dynamics simulations, making this a powerful case for a phase transition, nucleated in the extreme regime of high pressure, shear strain, and strain-rate generated by high energy
Summary
The structural and mechanical response of metals is intimately connected to phase transformations. The formation of a hexagonal (omega) phase was observed in recovered monocrystalline body-centered cubic tantalum of four crystallographic orientations subjected to an extreme regime of pressure, temperature, and strain-rate. This was accomplished using highenergy pulsed lasers. The objective of this report is to describe observations of a solid-solid phase transformation in monocrystalline tantalum with different orientations ([001], [110], [111], [123]), shock compressed at very short durations (~3 ns) and high strain rate (~108 s−1) in a uniaxial strain state These observations are backed by molecular dynamics simulations, making this a powerful case for a phase transition, nucleated in the extreme regime of high pressure, shear strain, and strain-rate generated by high energy www.nature.com/scientificreports/. The extreme stress state was created by six simultaneous incident laser pulses generating a pressure wave that penetrated into a capsule where a tantalum specimen was placed (Fig. 1); details are provided in the Methods Section
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
