Ye Hengqiang

Investigation on quenching at a high-angle Cu grain boundary on an atomic scale

We have performed molecular dynamics simulations of structural changes due to quenching the melting interface at a Cu Σ5(310)/[001] symmetrical tilt grain boundary. The simulation results suggest that the grain boundary structures due to quenching are different from those due to heating up to the same temperature. The calculated atom density profiles show that the grain boundary structures can be significantly changed as they are quenched to quite low temperatures.

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF LAVES PHASE STRENGTHENING NiAl BASE COMPOSITE FABRICATED BY RAPID SOLIDIFICATION

The Laves phase strengthening NiAl base composite was fabricated by conventionally casting and rapid solidification,and their microstructnre and mechanical properties were investigated together.The results exhibit that the Laves phase in the conventional cast alloy is relative coarse and distributes along the NiAl phase boundary.Moreover,small stick like Laves phase precipitates in the NiAl phase.Due to the segregation of Ni and Al in Laves phase,it still keeps the C14 crystal structure.The rapid solidification refines the NiAl and Laves phase greatly and promotes the formation of NiAl/Laves phase eutectic structure,which surrounds the NiAl phase and forms the cell like structure. However,the rapid solidification can not handicap the precipitation of needle-like Laves phase in the NiAl phase.But,the rapid solidification restrains the formation of α Cr phase.The compression tests show that the cell-like Laves phase strengthening NiAl base composite has better mechanical properties at ambient and elevated temperature,compared with the conventional cast alloy.The improvement of mechanical properties should be attributed to the cell-like Laves phase and the nanocrystallization of the cell-like Laves phase during high-temperature deformation.