In situ spherical B2 CuZr phase reinforced ZrCuNiAlNb bulk metallic glass matrix composite
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Haifeng Zhang,a) Huameng Fu, and Zhuang-Qi Hu Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Xiaoguang Yuan School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110870, China (Received 24 December 2009; accepted 23 February 2010)
In situ microlevel spherical B2 CuZr phase reinforced Zr49.5Cu36.45Ni4.05Al9Nb1 bulk metallic glass matrix composite was prepared successfully by the copper mold casting method. It was found that mechanical properties of Zr50.5Cu36.45Ni4.05Al9 alloy were improved largely due to the Nb addition. The room-temperature compressive fracture strength and plastic strain for Zr49.5Cu36.45Ni4.05Al9Nb1 rod with a diameter of 5 mm reaches 2037 MPa and 8%, respectively. The improvements are attributed to the precipitation of the spherical B2 CuZr phase distributed uniformly in amorphous matrix, which effectively hampers the propagation of shear bands by deflecting them at the interface and by a multiplication mechanism. I. INTRODUCTION
Monolithic bulk metallic glasses (BMGs) possess excellent mechanical properties, such as large elastic limit and high strength. However, most BMGs macroscopically exhibit limited plastic strain of 0% to 2% in compression and nearly zero in tension at room temperature, because the catastrophic failure is induced by highly localized shear bands (SBs).1–3 Therefore, more efforts have been made to improve the plasticity of BMGs. Among them, introducing a second phase into the metallic glass matrix is one of the practicable ways to enhance the mechanical properties of BMGs. For example, continuous malleable metal fiber,4,5 discontinuous metal powder,6,7 and refractory ceramic8 were introduced into amorphous matrix, and in situ microlevel9–12 and nanolevel13–15 precipitated phases, especially the ductile dendritic b-phase with body-centered-cubic structure9,10 in metallic glass matrix during solidification. Though in situ composites usually have more improved mechanical properties than ex situ ones, because of the stronger interfacial cohesion and good distribution, to pinpoint the appropriate composition and solidification condition is more difficult. In addition, the properties of the aforea)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0138 J. Mater. Res., Vol. 25, No. 6, Jun 2010
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mentioned BMG composites usually were examined using the small sample with a diameter of less than 3 mm. Recently, it was reported16–20 that the improvements of mechanical properties of the Cu–Zr–Al, Cu–Zr–Ti BMG composites are mainly related to the precipitation of the B2 CuZr phase, which is a ductile intermetallic known as the shape-memory compound.21 However, the critical casting thickness of composites are usually small. Thus, much more attention should be paid to improve the mechanical properties and critical casting thickness compatibly. In this work, a large size
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