TY - JOUR
T1 - Growth kinetics of cellular precipitation in a Mg-8.5Al-0.5Zn-0.2Mn (wt.%) alloy
AU - Contreras-Piedras, Edgar
AU - Esquivel-Gonzalez, Ramón
AU - López-Hirata, Víctor M.
AU - Saucedo-Muñoz, M. L.
AU - Paniagua-Mercado, Ana M.
AU - Dorantes-Rosales, Héctor J.
PY - 2010/11/15
Y1 - 2010/11/15
N2 - Microstructural evolution and growth kinetics were studied in an isothermally aged Mg-8.5Al-0.5Zn-0.2Mn (wt.%) alloy by means of X-ray diffraction, scanning electron microscopy, Vickers hardness measurements and transmission electron microscopy. Specimens were solution-treated and then aged at 373, 473 and 573K for different time period. The characterization results indicated the presence of both continuous and discontinuous precipitations of the Mg17Al12-γ phase in a Mg-rich matrix. The discontinuous or cellular precipitation was present with a lamellar structure, and the growth kinetics was evaluated using the Johnson-Mehl-Avrami-Kolmogorov equation analysis, which gives a time exponent close to 1. This value confirms that cellular precipitation takes place on the saturation sites corresponding to grain boundaries. In addition, the activation energy for cellular precipitation was determined to be about 64.6kJmol-1. This also indicates a grain boundary diffusion process. The variation of cellular spacing with temperature follows the behavior expected by Turnbull theory. The highest hardness peak corresponded to the lowest aging temperature and it is associated with a fine continuous precipitation; while the lowest hardness peak was detected at the highest aging temperature and it is attributed to the rapid coarsening process of both precipitations.
AB - Microstructural evolution and growth kinetics were studied in an isothermally aged Mg-8.5Al-0.5Zn-0.2Mn (wt.%) alloy by means of X-ray diffraction, scanning electron microscopy, Vickers hardness measurements and transmission electron microscopy. Specimens were solution-treated and then aged at 373, 473 and 573K for different time period. The characterization results indicated the presence of both continuous and discontinuous precipitations of the Mg17Al12-γ phase in a Mg-rich matrix. The discontinuous or cellular precipitation was present with a lamellar structure, and the growth kinetics was evaluated using the Johnson-Mehl-Avrami-Kolmogorov equation analysis, which gives a time exponent close to 1. This value confirms that cellular precipitation takes place on the saturation sites corresponding to grain boundaries. In addition, the activation energy for cellular precipitation was determined to be about 64.6kJmol-1. This also indicates a grain boundary diffusion process. The variation of cellular spacing with temperature follows the behavior expected by Turnbull theory. The highest hardness peak corresponded to the lowest aging temperature and it is associated with a fine continuous precipitation; while the lowest hardness peak was detected at the highest aging temperature and it is attributed to the rapid coarsening process of both precipitations.
KW - Cellular precipitation
KW - Growth kinetics
KW - Mg-Al-Zn alloys
UR - http://www.scopus.com/inward/record.url?scp=77957678758&partnerID=8YFLogxK
U2 - 10.1016/j.msea.2010.08.052
DO - 10.1016/j.msea.2010.08.052
M3 - Artículo
SN - 0921-5093
VL - 527
SP - 7775
EP - 7778
JO - Materials Science and Engineering A
JF - Materials Science and Engineering A
IS - 29-30
ER -