title: Drastic influence of minor Fe or Co additions on the glass forming ability, martensitic transformations and mechanical properties of shape memory Zr-Cu-Al bulk metallic glass composites.
abstract: The microstructure and mechanical properties of Zr48Cu48 -xAl4Mx(M ≡ Fe or Co,x= 0, 0.5, 1 at.%) metallic glass (MG) composites are highly dependent on the amount of Fe or Co added as microalloying elements in the parent Zr48Cu48Al4material. Addition of Fe and Co promotes the transformation from austenite to martensite during the course of nanoindentation or compression experiments, resulting in an enhancement of plasticity. However, the presence of Fe or Co also reduces the glass forming ability, ultimately causing a worsening of the mechanical properties. Owing to the interplay between these two effects, the compressive plasticity for alloys withx= 0.5 (5.5% in Zr48Cu47.5Al4Co0.5and 6.2% in Zr48Cu47.5Al4Fe0.5) is considerably larger than for Zr48Cu48Al4or the alloys withx= 1. Slight variations in the Young's modulus (around 5-10%) and significant changes in the yield stress (up to 25%) are also observed depending on the composition. The different microstructural factors that have an influence on the mechanical behavior of these composites are investigated in detail: (i) co-existence of amorphous and crystalline phases in the as-cast state, (ii) nature of the crystalline phases (austenite versus martensite content), and (iii) propensity for the austenite to undergo a mechanically-driven martensitic transformation during plastic deformation. Evidence for intragranular nanotwins likely generated in the course of the austenite-martensite transformation is provided by transmission electron microscopy. Our results reveal that fine-tuning of the composition of the Zr-Cu-Al-(Fe,Co) system is crucial in order to optimize the mechanical performance of these bulk MG composites, to make them suitable materials for structural applications.
authors.affiliation: Departament de Física, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: González
authors.affiliation: Departamento de Metalurgia Física, Centro Nacional de Investigaciones Metalúrgicas, CENIM, CSIC, Avda. Gregorio del Amo 8, E-28040 Madrid, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Pérez
authors.affiliation: Servei de Microscòpia, Universitat Autònoma de Barcelona, E-08193 Bellaterra Spain.
authors.forename: Emma
authors.initials: E
authors.lastname: Rossinyol
authors.affiliation: Departament de Física, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Suriñach
authors.affiliation: Departament de Física, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Dolors Baró
authors.affiliation: Departament de Física, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Pellicer
authors.affiliation: Institució Catalana de Recerca i Estudis Avançats (ICREA) and Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Sort
keywords: Cu–Zr–Al–(Fe, Co); composite; martensitic transformation; metallic glass; nanoindentation; plasticity; shape memory alloy