Phase stability and consolidation of glassy/nanostructured Al 85 Ni 9 Nd 4 Co 2 alloys
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M. Calin Fachgebiet Physikalische Metallkunde, Fachbereich 11-Material- und Geowissenschaften, Technische Universität Darmstadt, D-64287 Darmstadt, Germany; and Materials Science and Engineering Faculty, University “Politehnica” of Bucharest, R-060032 Bucharest, Romania
M. Branzei Materials Science and Engineering Faculty, University “Politehnica” of Bucharest, R-060032 Bucharest, Romania
L. Schultz Institut für Metallische Werkstoffe, IFW Dresden, D-01171 Dresden, Germany
J. Eckertb) Fachgebiet Physikalische Metallkunde, Fachbereich 11-Material- und Geowissenschaften, Technische Universität Darmstadt, D-64287 Darmstadt, Germany; and Institut für Komplexe Materialien, IFW Dresden, D-01171 Dresden, Germany (Received 3 June 2006; accepted 2 August 2006)
Al85Ni9Nd4Co2 metallic glass/nanostructured ribbons and powders were used as starting materials for producing bulk amorphous/nanostructured Al-based alloys. Glassy ribbons were obtained by melt spinning at wheel surface velocities ranging from 5 to 37 m/s. The amorphous ribbons exhibited a supercooled liquid region of ∼20 K, a reduced glass transition temperature of ∼0.47 and ␥ ∼ 0.328. Mechanical alloying of the elemental powder mixture did not lead to amorphization. However, amorphous powders obtained by milling the glassy ribbons for 9 h exhibited a thermal stability similar to the initial ribbons. Isothermal differential scanning calorimetry measurements were used to determine the consolidation parameters of the glassy powders. Consolidation at 513 K by uniaxial hot pressing and hot extrusion indicated that the former method leads to bulk glassy samples, whereas the latter one yields nanostructured ␣-Al/glassy matrix composites. I. INTRODUCTION
The development of lightweight alloys is of great importance for meeting new requirements in various fields, i.e., for transportation systems and energy consumption. In this context, aluminum- and titanium-based alloys have achieved major importance for advanced structural applications due to their high specific strength combined with good corrosion resistance.1,2 On the other hand, bulk metallic glasses (BMGs) have potential for applications as new high-strength structural materials due to a)
Address all correspondence to this author. e-mail address: [email protected] and [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www. mrs.org/jmr_policy. DOI: 10.1557/JMR.2007.0156 J. Mater. Res., Vol. 22, No. 5, May 2007
their excellent mechanical properties such as high elastic modulus and strength in comparison with their corresponding crystalline counterparts.3,4 The achievement of BMG formation3,4 and new types of marginal glassforming systems such as Al-TM-RE alloys (TM ⳱ transition metal, RE ⳱ rare-earth metal)5–9 has extended the understanding of some of the basic factors underlying glass formation. A remarkable characteristic of these aluminum-based alloy syst
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