Modeling the Age-Hardening Behavior of SiC/Al Metal Matrix Composites

Abstract

A model for the age-hardening behavior of SiC/Al metal matrix composites has been developed to describe the variation of the yield strength with aging time. The model incorporates the heterogeneous nucleation and growth of the precipitates along the dislocations to describe the accelerated aging behavior. It has been shown that the size and volume fraction of the SiC particles as well as aging temperature influence the age-hardening behavior. Increasing the aging temperature accelerates the aging process by increasing the velocities of the total nucleation rate (the sum of the nucleation per unit time) and growth of the precipitates due to the enhanced diffusion velocity of the solute atoms. Decreasing the size and increasing the volume fraction of the SiC particles also accelerate the aging process by enhancing the total nucleation rate due to the increased dislocation density. It was found that the yield strengths have been well predicted by the model for both SiC-reinforced Al-Cu-Mg alloy and Al-Mg-Si alloy, which have plateshaped and needle-shaped precipitates, respectively.

Experimental and Modeling of the Coupled Influences of Variously Sized Particles on the Tensile Ductility of SiC p /Al Metal Matrix Composites

“…Based on that conclusion, the tensile ductility as a function of the aging time and aging temperature can be calculated, if we can calculate the volume fraction and size of the precipitates as a function of the aging time and temperature. A previous work [29] developed a model for quantifying the aging-hardening behavior of the SiC p /Al metal matrix composites, and the model predictions are in reasonable agreement with the experimental data for both SiC p /Al-Cu-Mg and SiC p /Al-Mg-Si composites. Detailed information about the model can be found in Reference 29.…”

“…[29] Here, both the calculations [29] and experiments have been performed to determine the evolution of both the size and volume fraction of the precipitates. Figure 4 illustrates the model-predicted [29] and experimentally determined data for the size and volume fraction of the precipitates in SiC p /Al-Cu-Mg composites as a function of the aging time and aging temperature. Before aging, all the specimens are subjected to ELF treatment, to eliminate the effect of the formation of the constituents on the evolution of the precipitates.…”

“…The underestimation at the underaged stage is due to the growth velocity of the precipitates. In the aging-hardening model, [29] the growth rate of the precipitates has been supposed to remain constant with the aging time when the strengthening mechanism is cutting the precipitates through dislocation. However, in practice, the precipitation velocities have the highest values at the very beginning of aging and then start to decrease with aging time until a balance between the precipitation and the dissolution of the precipitates is reached.…”

Effects of TiB2 particles on aging behavior of in-situ TiB2/Al–Cu–Mg composites

“…For Zone I, there is a high dislocation density, which can serve as the nucleation sites for the precipitates, thus the precipitation is accelerated to form such a zone abundant in a large amount of precipitates [9,[21][22][23][24][25].…”

Evaluation of strain caused by coherent precipitates in an Al alloy using TEM techniques

“…On the other hand, there have been also some attempts to quantify elastic strains which are caused by coherent ordered precipitates and ceramic reinforcements in metallic alloys [3,4]. The elastic strain gradient's importance relies on the possibility of including them in the mechanical properties predictions that some theoretical models have, mainly due to alteration of aging kinetics as well as dislocations mobility [5,6]. One alloy on which aging produces nanoscale precipitates as well as strain fields (due to the different lattice parameter values) is the 2024 Al alloy used in aeronautic applications [7].…”