ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Experiments were conducted on an Al-0.2wt.%Sc alloy to evaluate the effect of equalchannelangular pressing (ECAP) on its creep behaviour. ECAP was conducted at room temperaturewith a die that had an internal angle of 90° between the two parts of the channel. The subsequentextrusion passes were performed by route BC up to 8 ECAP passes. Creep tests in tension wereperformed on the as-pressed samples at 473 K under an applied stress range between 10 to 50 MPa.For comparison purposes, some creep tests were performed also on the unpressed alloy. FollowingECAP and creep testing, samples were prepared for examination by means of transmission electronmicroscopy (TEM) and scanning electron microscopy (SEM) equipped with an electron backscattering diffraction (EBSD) unit. The observation of the surface of the ECAPed samples aftercreep exposure showed the occurrence of mesoscopic shear bands. The EBSD data reveal that thesebands are separated by high angle grain boundaries. The creep resistance of an alloy is a littledecreased after one ECAP pass. However, successive ECAP pressing lead to a noticeable decreaseof the creep properties. Thus, the Al-0.2wt.%Sc alloy processed by 8 ECAP passes exhibited fastercreep rate by about two and/or three orders of magnitude than the unpressed alloy when creeptesting at 473 K and at the same applied stress. The detrimental effect of ECAP on the creepresistance is probably a consequence of a synergetic effect of mesoscopic sliding of groups ofgrains along shear bands, more intensive grain boundary sliding and creep cavitation in creep of theultrafine-grained material
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.584-586.846.pdf
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