TY - JOUR
T1 - Homogeneous and heterogeneous precipitation mechanisms in a binary Mg-Nd alloy
AU - Choudhuri, D.
AU - Dendge, N.
AU - Nag, S.
AU - Meher, S.
AU - Alam, T.
AU - Gibson, M. A.
AU - Banerjee, R.
N1 - Funding Information:
Acknowledgement The authors gratefully acknowledge the Center for Advanced Research and Technology (CART) at the University of North Texas. CAST Cooperative Research Centre (CAST CRC) was established under, and is supported in part by, the Australian Government’s Cooperative Research Centres scheme. MAG would like to acknowledge the technical assistance of Mrs. M. Gershenzon and Mr. A. Yob in the HPDC of the samples used in this work.
PY - 2014/10
Y1 - 2014/10
N2 - Parallel modes of precipitation mechanisms in an Mg-Nd alloy were revealed by examining an isothermally annealed high pressure die cast alloy at 177 &Deg;C for up to 100 h. Broadly, precipitate evolution was observed to occur concurrently on dislocations and within the surrounding α-Mg matrix. However, it was observed that the presence of dislocation accelerated the precipitate formation kinetics significantly. In contrast to the accepted precipitation pathway in the Mg-Nd system, i.e., SSSS → GP zones → β'' → β' → β1 → β → βe, dislocations were found to preferentially facilitate the formation of β' and β1 precipitates even at the very early stages (5 h) of annealing. Within the same time frame, a homogeneous distribution of Nd-rich pockets was observed throughout the α-Mg matrix, along with the β' and β1 precipitates decorating dislocation lines. Results further indicate that these Nd-rich regions initiated precipitation within the parent α-Mg matrix. The formation of these Nd-rich pockets was explained on the basis of a miscibility gap in the α-Mg phase at 177 &Deg;C. Our results demonstrate that the presence of dislocations influence strongly the phase-transformation pathways in Mg-rare earth alloys by facilitating the formation of selective precipitate phases.
AB - Parallel modes of precipitation mechanisms in an Mg-Nd alloy were revealed by examining an isothermally annealed high pressure die cast alloy at 177 &Deg;C for up to 100 h. Broadly, precipitate evolution was observed to occur concurrently on dislocations and within the surrounding α-Mg matrix. However, it was observed that the presence of dislocation accelerated the precipitate formation kinetics significantly. In contrast to the accepted precipitation pathway in the Mg-Nd system, i.e., SSSS → GP zones → β'' → β' → β1 → β → βe, dislocations were found to preferentially facilitate the formation of β' and β1 precipitates even at the very early stages (5 h) of annealing. Within the same time frame, a homogeneous distribution of Nd-rich pockets was observed throughout the α-Mg matrix, along with the β' and β1 precipitates decorating dislocation lines. Results further indicate that these Nd-rich regions initiated precipitation within the parent α-Mg matrix. The formation of these Nd-rich pockets was explained on the basis of a miscibility gap in the α-Mg phase at 177 &Deg;C. Our results demonstrate that the presence of dislocations influence strongly the phase-transformation pathways in Mg-rare earth alloys by facilitating the formation of selective precipitate phases.
UR - https://www.scopus.com/pages/publications/84905659037
U2 - 10.1007/s10853-014-8404-z
DO - 10.1007/s10853-014-8404-z
M3 - Article
AN - SCOPUS:84905659037
SN - 0022-2461
VL - 49
SP - 6986
EP - 7003
JO - Journal of Materials Science
JF - Journal of Materials Science
IS - 20
ER -