In some systems, including copper niobium, it has been found that as the scale of the two phases decreases, there is an anomalous increase in strength. Mechanisms of this strengthening have been postulated, but a general theory has yet to be developed. A model system to study the co-deformation of fine scale materials was developed and characterized. An aluminum 18.5at.% zinc alloy was selected and discontinuously precipitated to produce 100% transformation and an interlamellar spacing of 240nm.The material was tested using strain rate jump tests to determine the temperature sensitivity, tensile tested to determine work hardening and the temperature sensitivity, wire drawn to study the effect of large plastic deformation and finally tension compression tested to determine internal stresses. The bulk properties of the two phases are well known allowing for a detailed analysis of the composite properties when combined with the mechanical results. The material showed increased strength above the rule of mixture prediction from bulk properties due to a fine scale microstructure . Although the lamellar material had a much higher strength than the rule of mixtures would predict, the overall strength of the alloy did not approach that of more conventional high strength aluminum alloys. The material was found to be temperature and rate dependent, with an increased work hardening rate as the temperature was decreased. Temperature was found to play a key role in the stress partitioning between the two phases. Temperature dependent relaxation processes lowered the stress partitioning between the hard and soft phases as the temperature was increased. Therefore, stress relaxation must be minimized to maximize the strengthening found in fine scale materials.

In some systems, including copper niobium, it has been found that as the scale of the two phases decreases, there is an anomalous increase in strength. Mechanisms of this strengthening have been postulated, but a general theory has yet to be developed. A model system to study the co-deformation of fine scale materials was developed and characterized. An aluminum 18.5at.% zinc alloy was selected and discontinuously precipitated to produce 100% transformation and an interlamellar spacing of 240nm.The material was tested using strain rate jump tests to determine the temperature sensitivity, tensile tested to determine work hardening and the temperature sensitivity, wire drawn to study the effect of large plastic deformation and finally tension compression tested to determine internal stresses. The bulk properties of the two phases are well known allowing for a detailed analysis of the composite properties when combined with the mechanical results. The material showed increased strength above the rule of mixture prediction from bulk properties due to a fine scale microstructure . Although the lamellar material had a much higher strength than the rule of mixtures would predict, the overall strength of the alloy did not approach that of more conventional high strength aluminum alloys. The material was found to be temperature and rate dependent, with an increased work hardening rate as the temperature was decreased. Temperature was found to play a key role in the stress partitioning between the two phases. Temperature dependent relaxation processes lowered the stress partitioning between the hard and soft phases as the temperature was increased. Therefore, stress relaxation must be minimized to maximize the strengthening found in fine scale materials.

In some systems, including copper niobium, it has been found that as the scale of the two phases decreases, there is an anomalous increase in strength. Mechanisms of this strengthening have been postulated, but a general theory has yet to be developed. A model system to study the co-deformation of fine scale materials was developed and characterized. An aluminum 18.5at.% zinc alloy was selected and discontinuously precipitated to produce 100% transformation and an interlamellar spacing of 240nm.The material was tested using strain rate jump tests to determine the temperature sensitivity, tensile tested to determine work hardening and the temperature sensitivity, wire drawn to study the effect of large plastic deformation and finally tension compression tested to determine internal stresses. The bulk properties of the two phases are well known allowing for a detailed analysis of the composite properties when combined with the mechanical results. The material showed increased strength above the rule of mixture prediction from bulk properties due to a fine scale microstructure . Although the lamellar material had a much higher strength than the rule of mixtures would predict, the overall strength of the alloy did not approach that of more conventional high strength aluminum alloys. The material was found to be temperature and rate dependent, with an increased work hardening rate as the temperature was decreased. Temperature was found to play a key role in the stress partitioning between the two phases. Temperature dependent relaxation processes lowered the stress partitioning between the hard and soft phases as the temperature was increased. Therefore, stress relaxation must be minimized to maximize the strengthening found in fine scale materials. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Les verres métalliques sont des matériaux amorphes, présentant d'excellentes propriétés mécaniques à température ambiante (haute limite d'élasticité, large domaine élastique, dureté élevée, etc.) combinées à une grande capacité de mise en forme au-delà de leur transition vitreuse. Leur domaine d'application est cependant limité par leur relative fragilité à température ambiante. Dans l'optique d'élargir le champ d'application des verres métalliques, l'élaboration par co-déformation à chaud de multi-matériaux alliant verre métallique et alliage léger traditionnel s'avère prometteuse. Dans ce travail, nous nous sommes intéressés à la possibilité d'élaborer par co-pressage à chaud des stratifiés associant un verre métallique base-zirconium à un alliage de magnésium. L'étude des propriétés mécaniques des deux matériaux, et notamment de leur comportement à chaud, a permis de préciser les mécanismes de déformation associés et de sélectionner les conditions optimales de co-pressage. Une caractérisation structurale des matériaux avant et après mise en forme a été réalisée. Les interfaces verre métallique/alliage de magnésium ont été caractérisées, confirmant une bonne adhésion entre les deux matériaux et des essais mécaniques spécifiques ont été mis en œuvre pour quantifier la tenue mécanique en cisaillement des interfaces. Ces résultats ont permis de valider le procédé de co-pressage à chaud comme technique d'élaboration de multi-matériaux verre métallique / alliage léger. / Metallic glasses are amorphous materials displaying very interesting mechanical properties at room temperature (high fracture stresses, large elastic domain, etc.) together with an excellent formability above the glass transition temperature. However the use of these materials is limited by their lack of plasticity at room temperature. In order to extend their applications field, it could be of interest to associate metallic glasses with conventional light alloys. In this work, the feasibility of the elaboration of multilayered materials involving a Zr-based metallic glass and a magnesium alloy by co-pressing at high temperature has been investigated. The selected conditions for co-pressing were chosen from the knowledge of the rheological behavior of both the metallic glass and the light alloy. The structural characterization of the materials before and after the elaboration has been studied. The interfaces metallic glass/magnesium alloy has been characterized, revealing a good bonding between the two materials. In order to evaluate the mechanical strength of the bonding, specific tests have been developed. The results enabled us to valid the co-pressing process as a technique to elaborate multimaterials associating metallic glasses with light alloys.