TY - JOUR
T1 - Isothermal coarsening of dendritic equiaxial grains in Al15.6wt.%Cu alloy
AU - Poirier, D. R.
AU - Ganesan, S.
AU - Andrews, M.
AU - Ocansey, P.
N1 - Funding Information:
Two of the authors (S.G. and P.O.) are especially grateful to the Alcoa Technical Center for financial support during their graduate studies. Dr. D. Zipperian, Manager of Buehler Southwest, graciously allowed us to use the Buehler facility in the Arizona Materials Laboratory. The assistance of Ms. L. Poirier in performing some of the quantitative metallography is very much appreciated.
PY - 1991/12/14
Y1 - 1991/12/14
N2 - The isothermal coarsening of equiaxial dendritic grains in Al15.6wt.%Cu alloy at 826 K (5 K above the eutectic temperature) was studied. For very short times (less than 60 s), the structure ripened by the usual increase in the secondary dendrite arm spacing. The secondary arms also coalesced and liquid inclusions formed within the grains. Simultaneously there was some fragmentation, in that the average center-to-center distance λ between grains at first decreased and then, at approximately 400 s, λ increased chth time. For times greater than 900 s, λ increased very slowly, and the morphology of the grains changed from dendritic globular to globular, when the original dendritic structure was no longer discernible. Using the surface-area-to-volume ratio Sv of the solid as the characteristic metric, a kinetic analysis showed that Ostwald ripening could not explain the results. Coalescence was identified as a mechanism, but unlike previous work, a t- 1 3 dependence of Sv on time t was not observed.
AB - The isothermal coarsening of equiaxial dendritic grains in Al15.6wt.%Cu alloy at 826 K (5 K above the eutectic temperature) was studied. For very short times (less than 60 s), the structure ripened by the usual increase in the secondary dendrite arm spacing. The secondary arms also coalesced and liquid inclusions formed within the grains. Simultaneously there was some fragmentation, in that the average center-to-center distance λ between grains at first decreased and then, at approximately 400 s, λ increased chth time. For times greater than 900 s, λ increased very slowly, and the morphology of the grains changed from dendritic globular to globular, when the original dendritic structure was no longer discernible. Using the surface-area-to-volume ratio Sv of the solid as the characteristic metric, a kinetic analysis showed that Ostwald ripening could not explain the results. Coalescence was identified as a mechanism, but unlike previous work, a t- 1 3 dependence of Sv on time t was not observed.
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U2 - 10.1016/0921-5093(91)90831-7
DO - 10.1016/0921-5093(91)90831-7
M3 - Article
AN - SCOPUS:0026397219
SN - 0921-5093
VL - 148
SP - 289
EP - 297
JO - Materials Science and Engineering A
JF - Materials Science and Engineering A
IS - 2
ER -