Influence of elastic inclusion morphology and matrix hardening behavior on bauschinger effect in metal matrix composites
- PDF / 212,699 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 88 Downloads / 207 Views
I. INTRODUCTION
AS any ductile solid, if the metal matrix composites (MMCs) composed of elastic particles or fibers embedded in a ductile metal matrix are initially deformed in tension or compression, the initial flow stress drop during reverse loading is remarkable, which is widely known as the Bauschinger effect (BE). Two main kinds of microscopic mechanism have been advanced to explain the BE.[1,2] One of the first is the theory of the long-range internal stress, which is created by dislocation pileup at barriers, Orowan loops, and the plastic incompatibility among grains and between particles and matrices. Another mechanism is the theory of the short-range internal stress, which is related to Orowan’s idea of the anisotropy in the resistance to dislocation motion. It is easier to move dislocations in the reverse than in the forward direction following prestrain. The shortrange internal stress can induce BE, even in superpure metal crystals. The BE in ductile two-phase materials has been widely investigated, both experimentally[3–9] and numerically.[8,9] It has been recognized that the BE in two-phase materials is much more pronounced than that in single-phase materials. This was ascribed to the fact that the long-range internal stress produced by the interaction between soft and hard phases is much higher than that over the scale of grain size in single-phase materials. It is therefore believed that the BE in MMCs is remarkable,[10–16] because the interaction between elastic particle and the soft matrix should be stronger than that in ductile two-phase materials. Numerical models[10,15] have been developed to show that even without considering the intrinsic BE of the matrix material, a significant BE exists in the corresponding composites reinforced with ceramic particles, such as SiC. A number of numerical simulations showed that the model ZHONGHUA LI, Professor, is with the School of Civil Engineering and Mechanics, Shanghai Jiaotong University, 200240, Shanghai Minhang, People’s Republic of China. S. SCHMAUDER, Professor, is with the Staatliche Materialpru¨fungsanstalt (MPA), University of Stuttgart, D-70569 Stuttgart, Germany. A. WANNER, Doctor, is with the Max-Planck Institute fu¨r Metallforschung, D-70174 Stuttgart, Germany. Manuscript submitted July 30, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
based on finite element (FE) analyses of a unit cell is a powerful method on relating the flow behavior of the composites to the inclusion volume fraction,[17,18,19] residual stress,[18] reinforcement shape[17,19] and matrix hardening.[17–20] However, relatively little attention has been paid to relate the BE of MMCs to its microstructures and the properties of the component phases. An axisymmetrical cell was first used by Llorca et al.[10] to predict the BE in a 2124 aluminum reinforced with 13.2 vol pct of SiC whiskers. Shi and Arsenault[15] employed a two-dimensional plane strain unit cell to analyze the BE in a 20 pct SiC whisker-reinforced 6061 Al composite, where the thermal residual stress accounts
Data Loading...
