Plasticity improvement of Zr 55 Al 10 Ni 5 Cu 30 bulk metallic glass by remelting master alloy ingots
- PDF / 917,724 Bytes
- 6 Pages / 584.957 x 782.986 pts Page_size
- 79 Downloads / 202 Views
nfu Li,a) Tao Lin, and Yaohe Zhou State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China (Received 5 June 2009; accepted 18 May 2009)
The effect of repeated melting of master alloy ingots on the bending properties of Zr55Al10Ni5Cu30 bulk metallic glass (BMG) was investigated. The bending plasticity of Zr55Al10Ni5Cu30 BMG was found to be improved with the increased remelting times. When the BMG sample cast from the master alloy ingot remelted 10 times is bent, it does not fracture even though the bending angle increases to 100 , but the maximum bending stress and elastic strain remain almost constant. The bending plasticity improvement may be attributed to the fact that the increased remelting times result in more free volume and more disordered and homogeneous microstructure in the BMG, which favors the initial nucleation of profuse shear bands and reduces the probability of catastrophic fracture.
I. INTRODUCTION
Multicomponent metallic glasses with excellent glassforming ability and high thermal stability have attracted much attention in recent years due to the feasibility of obtaining bulk amorphous samples using conventional solidification techniques at cooling rates as low as 1–100 K/s. Bulk metallic glasses (BMGs) possess high strength, hardness, and elastic deformation limit.1–5 However, during compressive or tensile testing at a temperature far below the glass transition temperature, they often break abruptly along a very narrow shear band, and exhibit little global plasticity.3,5 Such a catastrophic fracture greatly limits their application as structural materials, and much attention has been focused on the fracture mechanism and the plasticity improvement of the BMGs.6–11 Zr55Al10Ni5Cu30 BMG has good glass formation ability (maximum glassy rods of 30 mm in diameter)12 without noble metal and toxic elements, exhibiting a good application prospect as structural materials. On the other hand, previous investigations indicated that the as-cast Zr55Al10 Ni5Cu30 is a typical brittle BMG at room temperature, indicated by almost zero plasticity under tension13 and limited plasticity under compression.14–16 Furthermore, when it was bent no distinct plasticity was observed.17 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0430
3590
http://journals.cambridge.org
J. Mater. Res., Vol. 24, No. 12, Dec 2009 Downloaded: 13 Mar 2015
Meanwhile, some research has suggested that the plasticity of Zr55Al10Ni5Cu30 BMG could be improved by controlling the microstructure. For example, the compressive plasticity was enhanced by nanocrystals introduced into the matrix by injection casting with the low casting temperature18 or a nanoscale inhomogeneous microstructure introduced by low-temperature annealing,19 and bending plasticity was improved by fine homogeneously dispersed shear bands introduced by cold rolling.20 These results indicate that the microstructure plays
Data Loading...
