TY - JOUR
T1 - Formation process of unique microstructure in rapidly solidified Mg97Zn1Y2 alloy
AU - Nishida, Minoru
AU - Kawamura, Yoshihito
AU - Yamamuro, Takateru
N1 - Funding Information:
This work was supported by Grant-in-Aid for Scientific Research on Priority Areas (B) of “The Priority Group of Platform Science and Technology for Advanced Magnesium Alloys”, Ministry of Education, Science, Sports and Culture, Japan (Grant #11225203). The authors would like to their sincere appreciation to M/s. E. Aoyagi and Y. Hayasaka of HVEM Laboratory of Tohoku University, for their skillful support in TEM specimen preparation of RS powder.
PY - 2004/7
Y1 - 2004/7
N2 - The formation process of 6H-phase in rapidly solidified powder metallurgy (RS P/M) Mg97Zn1Y2 alloy has been investigated by transmission electron microscopy (TEM) observations. The initial microstructure of RS powder consists of equiaxed grains about 1μm in average diameter which is surrounded by Y and Zn rich amorphous grain boundaries. The 6H-phase was observed at grain boundaries in the RS ribbon prepared at circumferential speed of 42m/s. By lowering the circumferential speed, the 6H-phase at grain boundary in the RS ribbon changes to amorphous phase. The amount of Y and Zn segregation at the grain boundary in RS Mg97Zn1Y2 alloy increases with decreasing the cooling rate. In other words, the amorphization of grain boundary phase in RS alloy was promoted by the enrichment of Y and Zn. The growth of 6H-phase starts from grain boundary in the RS ribbon annealed at 573K for 1.2ks. It can be concluded that the 6H-phase in RS P/M Mg97Zn1Y2 alloy crystallizes in the Y and Zn rich amorphous phase at grain boundary and then grows into grain interior during extrusion. In order to clarify the stability of 6H-phase with heat treatment, microstructure changes in RS ribbon are also described.
AB - The formation process of 6H-phase in rapidly solidified powder metallurgy (RS P/M) Mg97Zn1Y2 alloy has been investigated by transmission electron microscopy (TEM) observations. The initial microstructure of RS powder consists of equiaxed grains about 1μm in average diameter which is surrounded by Y and Zn rich amorphous grain boundaries. The 6H-phase was observed at grain boundaries in the RS ribbon prepared at circumferential speed of 42m/s. By lowering the circumferential speed, the 6H-phase at grain boundary in the RS ribbon changes to amorphous phase. The amount of Y and Zn segregation at the grain boundary in RS Mg97Zn1Y2 alloy increases with decreasing the cooling rate. In other words, the amorphization of grain boundary phase in RS alloy was promoted by the enrichment of Y and Zn. The growth of 6H-phase starts from grain boundary in the RS ribbon annealed at 573K for 1.2ks. It can be concluded that the 6H-phase in RS P/M Mg97Zn1Y2 alloy crystallizes in the Y and Zn rich amorphous phase at grain boundary and then grows into grain interior during extrusion. In order to clarify the stability of 6H-phase with heat treatment, microstructure changes in RS ribbon are also described.
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U2 - 10.1016/j.msea.2003.10.145
DO - 10.1016/j.msea.2003.10.145
M3 - Article
AN - SCOPUS:3142696337
SN - 0921-5093
VL - 375-377
SP - 1217
EP - 1223
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
IS - 1-2 SPEC. ISS.
ER -