Deformation behavior of Zr- and Ni-based bulk glassy alloys
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Yuqiao Zeng and Albertus Deny Heri Setyawan Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
Nobuyuki Nishiyama R&D Institute of Metals and Composites for Future Industries (RIMCOF), Aoba-ku, Sendai 980-8577, Japan
Hidemi Kato Institute for Materials Research, Tohoku University, Aoba-Ku, Sendai 980-8577, Japan
Junji Saida Center for Interdisciplinary Research, Tohoku University, Aramaki, Aoba, Sendai 980-8578, Japan
Akihisa Inoue Institute for Materials Research, Tohoku University, Aoba-Ku, Sendai 980-8577, Japan (Received 6 November 2006; accepted 12 January 2007)
This article presents a comparative study of the deformation-induced structural changes observed within a glassy phase in two different Zr- and Ni-based alloys. Ductile Zr65Al7.5Ni10Pd17.5 bulk glassy alloy, which exhibits dynamic nanocrystallization forming a crystalline cubic phase within shear bands on plastic deformation, is presumed to contain pre-existing nuclei. On the contrary, no obvious dynamic nanocrystallization is observed within the shear bands in the glassy phase of the Ni50Pd30P20 bulk alloy, which, however, contains clear medium-range order zones on the order of 1 nm in size in an as-solidified state. This alloy exhibits nucleation and growth-transformation behavior on heating. At the same time, clear nucleation and growth of the cubic Ni-based phase are observed near the microcrack area in the deformed sample. High energy released at the time of the microcrack propagation caused nanocrystallization and blockage of the crack-tip propagation.
I. INTRODUCTION
At present, glassy alloys are attracting significant attention by materials scientists, owing to their promising physical and functional properties.1–3 These alloys, being metastable, devitrify on heating.4,5 However, it was found that plastic deformation of some Al–RE–TM (where TM stands for transition metals, and RE stands for rare-earth metals) amorphous alloys (e.g., Al90Fe5Gd5, Al90Fe5Ce5, and Al87Ni8.7Y4.3) at room temperature causes the precipitation of ␣-Al particles 7–10 nm in diameter within the shear bands on bending6 or nanoindentation.7 These nanocrystals have been identified as being the same type (cF4 ␣-Al) as those found during heat treatment at elevated temperatures. Under compressive testing, the nanoparticles were a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0126 J. Mater. Res., Vol. 22, No. 4, Apr 2007
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observed to form in the shear bands, while under tensile testing they were observed on the fracture surface only.8 It was shown that high-energy ball milling also produced nanocrystalline ␣-Al particles in the Al-based amorphous alloys.9 The deformation-induced crystallization has been also observed in the Zr65Cu17.9Ni14.6Al10Ti5 alloy under nanoindentation.10 However, one of the most remarkable results was the deformation-induced nanocrystallization of Zr65Al7.5Ni10Pd17.5,11 which caused its dr
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