The influences of multiscale-sized second-phase particles on ductility of aged aluminum alloys
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6/5/04
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The Influences of Multiscale-Sized Second-Phase Particles on Ductility of Aged Aluminum Alloys G. LIU, G.J. ZHANG, X.D. DING, J. SUN, and K.H. CHEN 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.
I.
INTRODUCTION
IN many materials, the microstructure often contains features at length scales ranging from nanometers to millimeters. The mechanical properties of materials observed at the macroscopic scale are correspondingly a type of homogenization of phenomena operating at these multilength lower scales. For the sake of quantitatively understanding how the multiscale microstructural features exert coupling effects on the mechanical properties, it is necessary to bring the detailed physics of the lower length scales up to the continuum models. This requires bridging the gaps that exist among the models and simulations at microscopic, mesoscopic, and continuum-length scales. This motivated the early multiscale material modeling that initially aimed to simulate the effects of interfaces on the macroscopic behavior of materials.[1] Subsequently, more and more interest has been focused on multiscale modeling. The areas of interest and the concerned subjects are simulating the plasticity and fracture of materials that deform and fracture at local microstructural inhomogeneity.[2,3,4] The microstructural inhomogeneity is mainly associated with the existence of void and second phase such as particles, fibers, whiskers, and so on, which, being commonly present in many materials, play very important roles in triggering the fracture process and then in determining the mechanical responses. As the primary materials of choice for application such as in aircraft, commercially aged aluminum alloys typically show the microstructural inhomogeneity by containing three types of differently sized second-phase particles, i.e., coarse ellipse-shaped constituents (from 5 to 30 m in diameter), intermediate sphere-shaped dispersoids (from 0.02 to 0.5 m in diameter), and fine disc- or needle-shaped strengthening precipitates (being smaller than 20 nm in the short axis).[5,6] G. LIU and G.J. ZHANG, Doctoral Students, X.D. DING, Associate Professor, and J. SUN, Professor and Director, are with the State Key Labor
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