The influences of multiscale-sized second-phase particles on ductility of aged aluminum alloys

Abstract

Commercially aged aluminum alloys commonly contain second-phase particles of three class sizes, and all contribute appreciably to the mechanical properties observed at the macroscopic scale. In this article, a multiscale model was constructed to describe the individual and coupling influences of the three types of second-phase particles on tensile ductility. The nonlinear relationships between the parameters of particles, including volume fraction, size, aspect ratio, shape, and ductility, were then quantitatively established and experimentally validated by the measured results from disc-shaped precipitate containing Al-Cu-Mg alloys and needle-shaped precipitate containing Al-Mg-Si alloys, as well as by using other researchers' previously published results. In addition, we discuss extending this model to predict the fracture toughness of aluminum alloys.

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

“…For simplicity, inner cracks are supposed to be particulate and distributed periodically in the form of cubical structure, while the precipitates and dispersoids are distributed uniformly and in orderly fashion within the ligaments, connecting two neighboring inner microcracks. [9][10][11][12] The schematic of the distribution is shown in Figure 2. [9][10][11][12] For simplicity, we assume that the size and interspacing of two neighboring microcracks are 2a and k, respectively.…”

“…[9][10][11][12] The schematic of the distribution is shown in Figure 2. [9][10][11][12] For simplicity, we assume that the size and interspacing of two neighboring microcracks are 2a and k, respectively. Thus, at a distance, r (r is the distance between two neighboring microcracks), the strain tensor TEM.…”

“…[6][7][8] Coarse ellipse/sphere-shaped constituents are~1 to 10 lm in diameter, intermediate sphere-shaped dispersoids are~50 to 500 nm, and fine disk/plate-shaped (for a 2XXX aluminum alloy), rod/ needle-shaped (for a 6XXX aluminum alloy), or sphereshaped (for a 7XXX aluminum alloy) precipitates are tens and hundreds of nanometers in diameter or length. [9] Previous studies [9][10][11][12] indicated that all three of these types of in-situ second-phase particles have important influences on the tensile ductility and fracture toughness of the aluminum alloys. The coarse constituents are brittle and initiate microcracks at low strain during deformation.…”

“…[13] Thus, to model the ductility and toughness of an aluminum alloy, the influences of these three types of in-situ second-phase particles should be included. Based on these three types of multiscaled in-situ second-phase particles distributed in the aluminum alloy, Liu et al [9][10][11][12] developed models for the tensile ductility and fracture toughness of Al alloys by taking constituents as inner cracks and deducing the specific expression of the microscopic plastic strain of the ligament. The model has been successfully used on 2XXX and 6XXX aluminum alloys.…”

“…The effects of the solution treatment, quenching, and aging procedures (which affect the sizes and volume fractions of the constituents and precipitates) on the tensile ductility and fracture toughness can be determined based on the models. [9][10][11][12] For SiC/Al metal matrix composites, four classes of particles, including SiC, and three types of in-situ second-phase particles (constituents, dispersoids, and precipitates) exist in the Al matrix. Figures 1(a) and (b) show the four classes of multiscaled particles in a typical SiC p /Al-Cu-Mg metal matrix composite.…”