Patent ID: 8323425
Filing Date: 2012-12-04
Classification: C22C,C22F

Abstract:
1. A method for non-isothermally aging an aluminum alloy comprising: heating an aluminum alloy at a first ramp-up rate to a maximum temperature below a precipitate solvus; when the aluminum alloy reaches the maximum temperature, cooling the alloy at a first cooling rate sufficient to produce a maximum number of primary precipitates wherein the first cooling rate is obtained by optimizing a precipitation growth rate and a nucleation rate using the following two equations: where N is the precipitate density number (number of precipitates per unit volume), N is the precipitation growth rate, D is the diffusion constant, r eq is the precipitate radius (also called precipitate size), r 0 is the value of C 0 is the mean solute concentration by atom percentage in the alloy matrix, C eq is the mean solute concentration by atom percentage in equilibrium precipitate-matrix interface, and α is the aspect ratio of precipitates, wherein the optimization is characterized by the maximization of and the minimization of after cooling the alloy at the first cooling rate, cooling the alloy at a second cooling rate until a minimum temperature is reached wherein the growth rate of primary precipitates is equal to or substantially zero, the second cooling rate being higher than the first cooling rate; and when the minimum temperature is reached, heating the alloy at a second ramp-up rate to a temperature sufficient to produce a maximum number of secondary precipitates; the first ramp-up rate, the first cooling rate, the second cooling rate, and the second ramp-up rate causing non-isothermal aging in which an aging temperature varies continuously with time.