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:
The effect of equal-channel angular extrusion (ECAE) on mechanical properties of anAA2017 produced by powder metallurgy is investigated. Special attention is given to the influenceof heat treatment, processing temperature and backpressure on the workability for achieving highstrength and moderate ductility. This is of special interest, since it is often reported that Al-Cualloys have low ductility and therefore are prone to cracking during severe plastic deformation. It isshown that ECAE at high temperatures (〉220°C) does not necessitate backpressure to ensurehomogeneous deformation but leads to a significant sacrifice in strength due to in-situ precipitation.Thus, most of the extrusions are done at considerably low temperatures. Performing roomtemperature-extrusion is most effective in achieving high strengths but also requires highbackpressures. Due to severe strain hardening during processing, the strength increase is combinedwith a reduction in ductility. Recently it was reported that a post-ECAE aging of pre-ECAE solutiontreated material is effective in enhancing the ductility of aluminium alloys. This approach wassuccessfully transferred to the current alloy. A high-temperature, short-time aging after only oneextrusion, for example, doubles the failure strain to a value of ~13%. Compared to the naturallyaged condition with coarse grains that serves as reference (T4), an increase of 15 % in yield stress(YS) was obtained while retaining the ultimate tensile stress (UTS). Another effective approach isthe combination of a pre-ECAE solution treatment with subsequent under-aging prior to ECAE. It isshown that performing ECAE at medium temperatures (160-180°C) enables a better workability andadditionally gives higher strengths and better ductility compared to the processing in the waterquenched condition. A remarkable YS of 530 MPa and an UTS of 580 MPa combined with amoderate failure strain of 11.6 % were achieved
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.584-586.685.pdf
