Linear sliding wear behavior of aluminium matrix composites reinforced by particulates

Linear sliding wear behavior studied for metal composites. Different types of composites were tested and three different fabrication techniques: two foundry techniques with different volume fraction and particulates size and thermal projection. The results show that the lubrication has a strong effect on the wear rate. The composites did not wear when tested under oil lubrication conditions, while the cable wore rapidly. The opposite phenomena occurred when dry tests were performed: the cable was protected while the specimen wore quickly. The critical volume fraction, i.e. the minimum volume fraction of particulates for protecting the composites, is on the order of 10%, whatever the size of the reinforcement. This minimum volume fraction does not seem to significantly depend on the size of the particulates. Finally, it was observed that the wear rate of the composite is the lowest for composites reinforced by a low percentage of particulates. A mechanical model describes the behavior of both partners (cable and MMC)

Intérêts technologiques et marchés potentiels des composites à matrice métallique : les actes du colloque

Il y a maintenant plus de trois décennies que les Composites à Matrice Métallique (CMM) ont vu le jour. Le développement d'un nouveau matériau passe par des phases différenciées jusqu'aux applications industrielles. Les CMM n'échappent pas à la règle. Dans les années 70-80, les études de prospective citaient de nombreuses applications potentielles pour les CMM. On attendait une révolution; les contraintes économiques et industrielles, associées à la faiblesse fâcheuse de quelques propriétés comme l'usinabilité ou la résistance à la corrosion, ont fait diverger significativement projections et développement réel. Aujourd'hui, l'enthousiasme du début a laissé la place à une maturité plus pragmatique dictée par la réalité industrielle: les applications naissent lentement, trop lentement, souvent hors du contexte des laboratoires de recherche universitaires, par exemple dans les PME. Il devenait nécessaire de préciser l'état de l'art sur les CMM, d'un point de vue scientifique aussi bien qu'industriel, mais surtout de mettre en relief les verrous technologiques, opposant un frein à leur développement, et les marchés potentiels de ces matériaux. Ce fut la vocation affichée de l'atelier franco-canadien qui s'est tenu en septembre 95 au Centre des Matériaux de l'Ecole des Mines de Paris, sous l'égide de la Conférence des Grandes Ecoles et du CNRS, et dont ce livre rassemble les travaux. Ce recueil, rédigé par les meilleurs spécialistes des CMM, permet de se convaincre de la réalité industrielle d'un nombre maintenant significatif d'applications ainsi que du devenir prometteur des CMM. Metallic Matrix Composites (MMC) were first developed more than three decades ago. The development of any new material must inevitably pass through different stages before reaching industrial applications and MMCs have been no exception to this rule. Numerous applications for these materials were foreseen during the 70s and 80s. The revolution which had been predicted however was muted by economic and industrial difficulties, associated with unenviable limitations such as their lack of machineability or their susceptibility to stress corrosion and this meant that their real development was very different from that had been projected. Today the initial enthusiasm has been replaced by a more mature pragmatism dictated by the needs of industry. Applications appear slowly, too slowly, often outside the confines of the university research laboratory, for example in SMEs. It had become necessary to re-examine the state of the art of MMCs, from the scientific as well as the industrial point of view and above all to identify the technological barriers limiting their development and to identify potential markets for these materials. Such were the declared aims of the Franco-Canadian workshop which was held in September 95 at the Centre des Matériaux under the aegis of the Conférence des Grandes Ecoles and the CNRS and which gave rise to these proceedings. This collection of papers, written by the greatest specialists on MMCs reveals the present industrial reality of a significant number of applications as well as the promising future of MMCs