| Abstract: | The effect of pure La and mischmetal(RE) on underside
shrinkage of ZA27 alloy with cooling rate of 32 min-1 was investigated. The results show that
the volumes of the underside shrinkage and the total shrinkage(underside shrinkage plus
internal shrinkage) of the alloy decrease as the content of La or RE increases. When the
contents of La and RE exceed 03%(mass fraction) respectively, the underside shrinkage is
eliminated and the internal shrinkage moves upwards gradually. The mechanism that the
underside shrinkage is eliminated is the falling of La and RE compounds and their
accumulation on the bottom of the ZA27 alloy sample. Since La and RE can not effectively
prevent phases(Al base solid solution) in the alloy from rising, the internal shrinkage is still
close to the bottom of the ZA27 sample. |
