ISSN:
1662-9779
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Physics
Notes:
Using molecular dynamics (MD) simulation, we have investigated the mechanicalproperties and the microstructural evolution of nanocrystalline tantalum (NC-Ta, grain size from 3.25nm to ~13.0 nm) under uniaxial tension. The results show the flow stress at a given offset straindecreases as the grain size is decreased within the grain size regime studied, implying an inverseHall-Petch effect. A strain rate sensitivity of ~0.14, more than triple that of coarse-grain Ta, is derivedfrom the simulation results. Twinning is regarded to be a secondary deformation mechanism based onthe simulations. Similar to nanocrystalline iron, stress-induced phase transitions from body-centeredcubic (BCC) to face-centered cubic (FCC) and hexagonal close-packed (HCP) structures take placelocally during the deformation process, The maximum fraction of FCC atoms varies linearly with thetensile strength. We can thus conclude that a critical stress exists for the phase transition to occur. It isalso observed that the higher the imposed strain rate, the further delayed is the phase transition. Suchphase transitions are found to occur only at relatively low simulation temperatures, and are reversiblewith respect to stress
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.139.83.pdf
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