Transition of dislocation glide to shear transformation in shocked tantalum

Journal Article · Tue Feb 28 00:00:00 EST 2017 · MRS Advances

DOI:https://doi.org/10.1557/adv.2017.236· OSTI ID:1347662

Hsiung, Luke L. ^[1]; Campbell, Geoffrey H. ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

A TEM study of pure tantalum and tantalum-tungsten alloys explosively shocked at a peak pressure of 30 GPa (strain rate: ~1 x 10⁴ sec^-1) is presented. While no ω (hexagonal) phase was found in shock-recovered pure Ta and Ta-5W that contain mainly a low-energy cellular dislocation structure, shock-induced ω phase was found to form in Ta-10W that contains evenly distributed dislocations with a stored dislocation density higher than 1 x 10¹² cm^-2. The TEM results clearly reveal that shock-induced α (bcc) → ω (hexagonal) shear transformation occurs when dynamic recovery reactions which lead the formation low-energy cellular dislocation structure become largely suppressed in Ta-10W shocked under dynamic (i.e., high strain-rate and high-pressure) conditions. A novel dislocation-based mechanism is proposed to rationalize the transition of dislocation glide to twinning and/or shear transformation in shock-deformed tantalum. Lastly, twinning and/or shear transformation take place as an alternative deformation mechanism to accommodate high-strain-rate straining when the shear stress required for dislocation multiplication exceeds the threshold shear stresses for twinning and/or shear transformation.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1347662
• Report Number(s): LLNL-JRNL-710038; applab
• Journal Information: MRS Advances, Vol. 2, Issue 27; ISSN 2059-8521
• Publisher: Materials Research Society (MRS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE