ISSN:
1662-9752
Quelle:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Thema:
Maschinenbau
Notizen:
The deformation mechanism in the nanometer grain size range has been basicallyinvestigated from the results of microstructural observation after superplastic deformation in aZn-Al eutectoid alloy in which a reverse grain size dependence of superplasticity was previouslyreported: flow stress increases and elongation decreases with decreasing grain size when grain sizeis markedly reduced to nanometer range. By controlling the aging condition after solution treatmentand subsequent quenching, two specimens are prepared: the as-quenched specimen with ultrafinegrains of 83nm in diameter and aged specimen with normally fine grains of 2.6μm. The elongationis confirmed to be smaller in the as-quenched specimen than in the aged specimen, although theflow stress is lower. As a result of TEM observation on the interior of the grains, dislocations arerare in the as-quenched specimen, while a significant density of dislocations are observed in theaged specimen. This result strongly supports the mechanism previously proposed by Mishra et al.that the accommodation process, i.e., the dislocation glide inside the grains, becomes more difficultwith decreasing grain size in the nanometer grain size range, even though the grain boundary slidingas the major process becomes facilitated. Roughly assessed m-value was in accord with thismechanism
Materialart:
Digitale Medien
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/16/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.551-552.153.pdf
