Shock-induced omega phase in tantalum
- Lawrence Livermore National Lab., CA (United States)
The deformation substructure developed within polycrystalline tantalum under a high shock pressure (45 GPa) with a 1.8 {micro}s duration has been examined using transmission electron microscopy. A shock-induced {beta} (bcc) {yields} {omega} (hexagonal) displacive transformation is observed for the first time within tantalum. Needle- or plate-like {omega} phase is found to form accompanied with the {l_brace}112{r_brace} type deformation twins within shock-recovered tantalum. The orientation relationships between the shock-induced {omega} and parent {beta} phases are determined to be {l_brace}10{bar 1}0{r_brace}{sub {omega}} {parallel} {l_brace}211{r_brace}{sub {beta}}, [0001]{sub {omega}} {parallel} <111>{sub {beta}} and <1{bar 2}10>{sub {omega}} {parallel} [0{bar 1}1]{sub {beta}}. The lattice parameters of {omega} phase are a{sub {omega}} = ({radical}2a{sub {beta}}) = 0.468 nm and c{sub {omega}} = ({radical}3/2) a{sub {beta}} = 0.286 nm (c/a = 0.611). Both deformation twins and shock-induced {omega} phase are primarily formed along the {l_brace}211{r_brace}{sub {beta}} slip planes with high resolved shear stresses, and have a common habit plane [i.e. the {l_brace}211{r_brace} plane] with the parent {beta} matrix. It is suggested that shear deformation on the {l_brace}211{r_brace} planes is the major cause for the formation of shock-induced {omega} phase within tantalum.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 619488
- Journal Information:
- Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 9 Vol. 38; ISSN SCMAF7; ISSN 1359-6462
- Country of Publication:
- United States
- Language:
- English
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