Tensile and Fatigue Behavior of Aluminum Oxide Fiber Reinforced Magnesium Composites: Part I. Fiber Fraction and Orienta
- PDF / 2,487,688 Bytes
- 8 Pages / 594 x 774 pts Page_size
- 19 Downloads / 227 Views
I.
INTRODUCTION
THE reinforcement of
metal matrices with high strength and high modulus synthetic fibers to produce a hybrid material possessing attractive structural properties is not a new concept. The combination of recently developed high strength and modulus ceramic fibers with lightweight, ductile metal matrices (principally magnesium and aluminum) has spurred renewed interest in the potential of these materials for applications requiring high specific strength and stiffness, toughness, and fatigue resistance. Implementation of advanced metal matrix composite materials in structural applications has always suffered, however, due to a lack of a quantitative relationship between microstructure and mechanical behavior. Although a great deal of work has been performed on fracture mechanisms in metal matrix composites, ~-4 the resuits to date have been quite contradictory in nature. The inconsistencies arise from the complex interaction of the fiber/matrix interfacial region with various applied states of stress. In addition, the presence of the fiber/matrix interface in these composites introduces several mechanisms of crack propagation in addition to those observed in monolithic materials. 5 Also, standard metallurgical techniques for modifying the properties of the matrix material ( i . e . , alloying, heat treatment, deformation processing, etc'.) affect the metallurgical structure and properties of the interfacial region as well .6.7 Thus, the effects of processing variables on composite behavior through microstructural changes in the matrix are difficult to separate from the effects of those variables on the fiber/matrix interface. A research program was initiated to overcome these difficulties by developing quantitative relationships between matrix microstructure, composition and properties, fiber orientation and volume percent, and fatigue crack growth behavior in these materials through direct observations of the effects of these variables on the strain field at the tip J. E. HACK and R. A. PAGE, Senior Research Metallurgists, and G. R. LEVERANT, Assistant Director, are with the Department of Materials Sciences, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78284. Manuscript submitted September 8, 1983. METALLURGICAL TRANSACTIONS A
of a growing crack. The program is aimed at determining the local sequence of events at the tip of a fatigue crack ( i . e . , matrix failure vs fiber failure vs interfacial decohesion) and the critical strain accumulation required for these events to occur. However, very little data exist on the relationships between microstructure and crack growth resistance in metal matrix composites. Hence, the initial phase of the overall program was designed to characterize the tensile and fatigue behavior of a model material. The results of that characterization will be presented in this paper while the crack tip strain characterizations will be reported at a later date.
II,
EXPERIMENTAL
The model material chosen for this study was commercially pure magnesium re
Data Loading...
