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Combining Equal-Channel Angular Extrusion (ECAE) and Heat Treatment for Achieving High Strength and Moderate Ductility in an Al-Cu Alloy (2008)

Hockauf, Matthias ; Meyer, Lothar W. ; Krüger, Lutz

s.l. ; Stafa-Zurich, Switzerland

Materials science forum Vol. 584-586 (June 2008), p. 685-690

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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

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Projektstudie zur Steuerung und Überwachung des Heilverfahrens (2000)

Kübke, Rainer A. ; Südkamp, Norbert P. ; Grotz, Josef ; [et al.]

Springer

Trauma und Berufskrankheit 2 (2000), S. S360

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ISSN: 1436-6274

Keywords: Schlüsselwörter Heilverfahrenssteuerung ; Behandlungsqualität ; Arbeitsunfall ; Keywords Occupational accident ; Quality ¶management ; Steering methods

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Description / Table of Contents: Abstract We present the results of a study conducted in collaboration with the German workers’ board to monitor the effectiveness of treatment in 477 cases. The examiners reviewed the charts of patients who had suffered distorsion or luxation of the knee, fractures of the spine with or without neural deficits, calcaneus fractures, rotator cuff lesions and shoulder luxation, and fractures of the acetabulum and pelvis as the result of accidents. A new documentation sheet was desiged to note administrative and medical data. All 477 patients’ charts and X-rays were reviewed by three trauma surgeons, and procedures were monitored in a prospective manner. The study revealed considerable discrepancies between the assumed injuries and those ultimately found to have been sustained, especially in the case of knee injuries. The article reveals the results concerning the validity of the diagnosis and the need for more precisely tailored diagnostic methods for different patient groups. Our final conclusion is that it is necessary to implement new paths of patient management and better steering features to improve both the quality of medical care and the administrative procedures in place.

Notes: Zusammenfassung Die Ergebnisse einer Studie zur Heilverfahrenssteuerung im BG-lichen Behandlungsverfahren für die Kenndiagnosen Distorsionen und Luxationen des Kniegelenks, Frakturen der Wirbelsäule mit und ohne neurologische Ausfälle, Frakturen des Fersenbeins, Rotatorenmanschettenrupturen und Schulterluxationen, Azetabulum- und Beckenfrakturen werden vorgestellt. Nach einem neu entwickelten Dokumentationsbogen wurden zunächst retrospektiv, dann auch prospektiv 477 BG-liche Patientenakten und Röntgenbilder von 3 Untersuchern nachvollzogen bzw. die Verfahren prospektiv begleitet. Die Untersuchung ergab besonders bei den Knieverletzungen erhebliche Abweichungen zwischen der angenommenen und der letztendlich tatsächlich eingetretenen Verletzungsdiagnose. Die prozentualen Aufschlüsselungen auch bezüglich der gerechtfertigten, übertriebenen oder unzureichenden Diagnostik werden diagnosebezogen im Einzelnen dargestellt. Zusammenfassend hat die Studie ergeben, dass sowohl auf ärztlicher Seite als auch in der Verwaltung nach neuen Wegen zur effektiven Heilverfahrenssteuerung gesucht werden muß.