Characterization of the Interface Between the Bulk Glass Forming Alloy Zr 41 Ti 14 Cu 12 Ni 10 Be 23 with Pure Metals an
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Konrad Samwer I. Physikalisches Institut, Universita¨t Go¨ttingen, 37075 Go¨ttingen, Germany
Frigyes Szuecs and William L. Johnson Keck Laboratory of Engineering Materials, California Institute of Technology, Pasadena, California 91125 (Received 20 December 1999; accepted 28 April 2000)
The reaction of the bulk glass forming alloy Zr41Ti14Cu12Ni10Be23 (Vit 1) with W, Ta, Mo, AlN, Al2O3, Si, graphite, and amorphous carbon was investigated. Vit 1 samples were melted and subsequently solidified after different processing times on discs of the different materials. Sessile drop examinations of the macroscopic wetting of Vit 1 on the discs as a function of temperature were carried out in situ with a digital optical camera. The reactions at the interfaces between the Vit 1 sample and the different disc materials were investigated with an electron microprobe. The structure and thermal stability of the processed Vit 1 samples were examined by x-ray diffraction and differential scanning calorimetry. The results are discussed in terms of possible applications for composite materials.
I. INTRODUCTION
In recent years there has been a considerable scientific and industrial interest in metal matrix composites as a way to improve mechanical properties compared to the unreinforced alloys.1–3 For matrix materials pure metals like, e.g., aluminum4 and titanium5 and recently bulk metallic glass (BMG) forming alloys,6–8 have been studied. BMGs have a high glass forming ability so that cooling rates of less than a 100 K/s are sufficient to circumvent crystallization. They have high yield strength and a high elastic strain limit combined with a good corrosion resistance and relatively high fracture toughness.9–12 However, the lack of tensile ductility can be a drawback in many applications. By the addition of particles to the BMG, an improved tensile ductility is expected because the particles encourage the formation of multiple shear bands and hinder the propagation of a single critical shear band. The properties of a composite are not only defined by the properties of the matrix and the reinforcement material but essentially by the chemical reaction of both. For
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 15, No. 7, Jul 2000
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particulate-reinforced BMG composites a strong reaction can lead to a dissolution of the particles, which can affect the glass forming ability of the BMG–matrix. On the other hand, a necessary condition for infiltration casting of composites is that the melt wets the particles. Additionally to the wetting condition, an optimized interfacial strength is essential to improve mechanical properties. For example, by the introduction of SiC particles in the bulk metallic glass former Cu 47 Ti 34 Zr 11 Ni 8 and Zr57Nb5Al10Cu15.4Ni12.6, it was found that the thermal stability was increased compared to the unreinforced material but no enhancement of the ductility was achieved because the interface bet
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