Bulk nanostructured Zr-based multiphase alloys with high strength and good ductility

Abstract

IFW Dresden, P.O. Box 27 00 16, D-01171 Dresden, Germany(Received August 21, 2000)(Accepted in revised form December 25, 2000)Keywords: Casting; Metallic glasses; Crystallization; Bulk nanostructured alloys; MechanicalpropertiesIntroductionAn increase in strength along with good ductility has recently been observed for a number of alloys withmultiphase nanoscale microstructures (1–4). In particular, partial crystallization of bulk metallicglass-forming alloys is a promising way for producing new bulk nanophase materials with outstandingmechanical properties at room temperature (5,6). Already homogeneous glassy alloys exhibit abeneficial combination of high yield strength, microplasticity on the order of about 1–2%, rather lowYoung’s moduli and high fracture toughness values as well as high wear resistance (7–9). Partialnanocrystallization can further improve these properties (1–4) and allows to obtain bulk nanostructuredalloys with promising potential as new engineering materials. As an example, this work reports on thesynthesis of bulk nanostructured (Zr/Ti)-Cu-Al-Ni alloys through devitrification of cast bulk glassyspecimens, and presents results for their mechanical properties at room and elevated temperatures.ExperimentalRods with 3 mm diameter and 50 mm length were prepared by arc-melting pure elements under argonatmosphere and casting into a copper mold. In order to restrict the oxygen content of the alloys to lessthan 0.2 at.% oxygen high purity starting materials (99.99% purity) were used and the casting wasperfomed under an argon atmosphere of 99.9999% purity. This gave fully amorphous specimens aftercasting. The samples were characterized by x-ray diffraction (XRD, Co Ka radiation), transmissionelectron microscopy (TEM) and differential scanning calorimetry (DSC) using a heating rate of 20Kmin