The effect of matrix microstructure on the tensile and fatigue behavior of SiC particle-reinforced 2080 Al matrix composites

Abstract

The effect of matrix microstructure on the stress-controlled fatigue behavior of a 2080 Al alloy reinforced with 30 pct SiC particles was investigated. A thermomechanical heat treatment (T8) produced a fine and homogeneous distribution of SЈ precipitates, while a thermal heat treatment (T6) resulted in coarser and inhomogeneously distributed SЈ precipitates. The cyclic and monotonic strength, as well as the cyclic stress-strain response, were found to be significantly affected by the microstructure of the matrix. Because of the finer and more-closely spaced precipitates, the composite given the T8 treatment exhibited higher yield strengths than the T6 materials. Despite its lower yield strength, the T6 matrix composite exhibited higher fatigue resistance than the T8 matrix composite. The cyclic deformation behavior of the composites is compared to monotonic deformation behavior and is explained in terms of microstructural instabilities that cause cyclic hardening or softening. The effect of precipitate spacing and size has a significant effect on fatigue behavior and is discussed. The interactive role of matrix strength and SiC reinforcement on stress within "rogue" inclusions was quantified using a finite-element analysis (FEA) unit-cell model.

Fatigue crack growth in SiC particle reinforced Al alloy matrix composites at high and low R-ratios by in situ X-ray synchrotron tomography

“…Furthermore, MMCs exhibit improved fatigue resistance over monolithic alloys. This fatigue resistance depends on a variety of factors, such as reinforcement particle volume fraction, particle size, matrix and interfacial microstructure, processinginduced inclusions or defects, and testing environment [2][3][4][5][6][7][8].…”

Temperature and Particle Size Influence on the High Cycle Fatigue Behavior of the SiC Reinforced 2124 Aluminum Alloy

“…The lower matrix strength, due to the overaging during testing, causes a general reduction in fatigue strength for all of the tested conditions at 180 • C [12]. Fatigue crack initiation in the matrix is the primary failure mechanism [7,20,23,36].…”

“…Further, dispersion strengthening occurs, which leads to two main mechanisms. Dislocation generation and the high dislocation density due to the difference in the thermal expansion coefficient of the matrix and the SiC particle [31], as well as the impediment of the dislocation movement due to the high dislocation density and the reinforcement component [4,12] act as strengthening mechanisms. An increase in particle volume fraction and a decrease in particle size lead to an enhancement of this effect, and therefore to a further increase in strength and a decrease in ductility [1,32].…”

“…Composites processed by powder metallurgy, as used in this study, exhibit a homogeneous particle distribution, and therefore superior mechanical properties and an outstanding fatigue performance when compared to other manufacturing processes [11]. Tensile strength and fatigue resistance of the composites are also strongly influenced by the aging condition and the matrix microstructure [12,13]. Particle shape [14,15], particle size, and volume fraction [16][17][18][19][20] are critical factors for the mechanical properties and fatigue behavior of the AMCs.…”

“…Therefore, the probability of particle failure increases [21,24]. Larger particles provide a minor resistance against particle failure [4,15,25] and fatigue cracks initiate preferably at them due to the higher local stress concentration [12,17,26]. In contrast, for composites with smaller particles, the stress distribution is more homogeneous due to minor local stress concentrations and smaller interparticle spacing [27].…”