Predicting Secondary-Dendrite Arm Spacing of the Al-4.5wt%Cu Alloy During Unidirectional Solidification

Abstract

Mechanical properties and performance of metallic materials depend on their microstructures. In order to develop engineering materials that match prescribed criteria and to enable design with multifunctional materials, it is essential to be able to predict their microstructural patterns, such as size, shape, and spacing of the dendritic structures observed in solidified metals. In the cases of metallic alloys, which present dendritic structure, the mechanical properties of foundry products depend mainly on the primary-and secondary-arm. Therefore, it is important, in a computational simulation of the solidification processes, to use reliable methods to correlate the thermal parameters with secondarydendrite arm spacing. This study presents a numerical model for prediction of secondary-arm spacing as a function of thermal parameters (cooling rates and local solidification time). Spacing of the arms for a binary alloy is numerically predicted using a phase-field model. Secondary dendrites calculated by phase-field model, they are similar to the ones found in experiments investigation of solidification in Al-Cu alloys. Arm spacing predicted in the present work, when compared with the experimental results, showed good agreement. Its estimation takes place at the late stage of growth. The effect of physical properties (partition coefficient (k e ), diffusion in the liquid (D L ) and diffusion in the solid phase (D S )) on secondary-arm spacing is systematically investigated by phase-field model. With the help of numerical results for Al-4.5wt%Cu alloy, the applicability of the phase-field model to the estimation of secondary-dendrite arm spacing during unidirectional solidification is demonstrated.

Experimental Investigation of Ternary Al-Si-Cu Alloy Solidified with Unsteady-State Heat Flow Conditions

“…The solidification thermal parameters have influence on the microstructure and microsegregation andthese, in turn, are key featuresin inducing non-uniformity on the as-cast material mechanical properties. For this reason, the microstructure and microsegregation has been extensively studied both theoretically [1][2][3][4][5][6][7][8][9][10][11] and experimentally [12][13][14][15][16][17][18][19][20][21][22][23][24][25] for the last decades. The Al-1.2wt%Pb and Al-3.2wt%Bi alloys have been chosen by Freitas et al 13 , to study the effect of microstructural parameters on the wear process.…”

“…where C S is the concentration in the solid region, C 0 the initial overall composition and F S the solid fraction. Although the influence of solidification speed (V L ) and cooling rate ( ) on the microstructural characteristics was the focus of many studies [1][2][3][4][12][13][14][15][16] , literature on the influence of these parameters on the microsegregation profiles are still quite limited 21 . Burton et al 9 proposed an equation for effective distribution coefficient (K ef ) as a function of the solidification speed (V L ).…”

Simulation and Experimental Validation of Secondary Dendrite Arm Spacing for AlSi7Mg0.3 Chassis Parts in Low Pressure Die Casting

“…The Solidification time is the time from the start of pouring to the time when the temperature locally falls below the Solidus temperature. The Liquidus to Solidus time is the elapsed time in the local transition from the Liquidus and Solidus temperatures [6,7].…”

An Experimental Study of the Solidification Thermal Parameters Influence upon Microstructure and Mechanical Properties of Al-Si-Cu Alloys

“…Currently a large part of the concepts and methods developed in support of solidification research, which is the main phenomenon that occurs during casting, can be applied on an industrial scale, allowing a visible improvement in the manufactured parts quality, making solidification studies a powerful tool for its economic potential 3 . The microstructure effects on metallic alloys properties has been highlighted in various studies and particularly, the grain size influence and dendrite arm spacing upon the mechanical properties has been reported 1,4 .…”

“…The ternary system (Aluminum, Silicon and Copper) has excellent properties as mechanical strength, low density as compared to ferrous alloys and good flowability. These properties make the system a good choice on automotive and aerospace industry, calling researchers attention 3,6 . Costa et al 7 investigated the influence of silicon on the microstructure comparing directional upward and horizontal solidification for the alloys Al-6wt%Cu-4wt%Si and Al-6wt%Cu, demonstrating that silicon alloying contributes to significant refinement of primary/secondary dendrite arm spacings.…”