Dissolution Kinetics of Spheroidal-Shaped Precipitates in Age-Hardenable Aluminum Alloys
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RODUCTION
HEAT-TREATABLE ALUMINUM alloys are widely used in industrial applications due to their high strength gained by various precipitates.[1] However, the presence of precipitated particles in the alloy matrix reduces the ductility of these alloys.[2,3] Solution heat treatment is commonly used to dissolve the particles into the matrix which increases the ductility of these alloys. Also, solution heat treatment may be used to make the supersaturated solid solutions needed for the subsequent age-hardening treatments. The optimum solution treatment schedule may be obtained by considering the kinetics of particle dissolution. In this regard, different studies concerning particle dissolution kinetics have been performed using a variety of analytical and numerical techniques.[4-11] Thomas and Whelan,[4] and Whelan[5] have proposed an analytical model for dissolving spherical-shaped particles during a solution process. In this model, it is assumed that the dissolving particle is located in an unbounded domain, and the dissolution is considered to be approximately the reverse of the precipitation growth. Tanzilli and Heckel[6] have used a numerical model by applying a finite difference method to investigate the dissolution of mono-sized particles in binary
NOZAR ANJABIN is with the Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz, Iran. Contact e-mail: [email protected] MAJID SEYED SALEHI is with the Department of Materials Science and Engineering, K. N. Toosi University of Technology, Tehran, Iran. Manuscript submitted January 15, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
alloys. In this model, diffusion-controlled moving boundaries with planar, cylindrical, and spherical interfaces have been considered during isothermal annealing. Tundal and Ryum[7] investigated the dissolution kinetics of spherical particles with a log-normal particle size distribution in binary alloys using a finite difference model. It was found that a size distribution of particles significantly affects the dissolution kinetics and should be considered in dissolution modeling. Vermolen et al.[8] proposed a numerical method for dissolution of the stoichiometric second phase Mg2Si in a ternary Al-Mg-Si alloy. It was assumed that all particles in the alloy have the same size and are equidistant from each other. Kovacˇevic´ and Sˇarler[9] used the phase-field method to study the kinetics of dissolution phenomena of second phase particles in a binary aluminum alloy during an isothermal homogenization process. Wang and Wang[10] predicted the kinetics of carbonitride dissolution in steels using a numerical method. The model can be applied for dissolution of spherical particles with equal size or having a particular size distribution in a finite austenite matrix at different annealing temperatures and durations. An analytical approach for dissolution kinetics of spherical precipitates in a multi-particle system has been presented by Zuo et al.[11] Their model is based on the combination of the Johnson–Me
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