Abstract
The mechanical properties of as-cast metallic materials depend strongly on the size and shape of grains,which are critical microstructural parameters dictated by the interplay of nucleation and growth of crys-talline solids during solidification.In our experiments,the microstructure transition from coarse colum-nar crystals into fine equiaxed crystals for dilute Al-Mn-Si alloys was achieved by using sub-rapid so-lidification with the addition of Al-5Ti-1B grain refiner.The average grain size of Al alloy was reduced from a millimeter size to 73 pm.Through temperature gradient calculation,we found that the acqui-sition of fine equiaxed crystals could be attributed to the existence of a high number density of TiB2,acting as effective nucleation sites with an increase in total undercooling.Furthermore,the curvature su-percooling,constitutional undercooling,thermal undercooling,and kinetic undercooling during sub-rapid solidification were quantitatively determined for given solidification rates.Our results showed that con-stitutional undercooling,rather than thermal undercooling,was primarily responsible for the formation of fine equiaxed grains,with the assistance of Al-5Ti-1B grain refiner.This work provides a new insight into the grain refining mechanism under sub-rapid solidification.
基金项目
National Natural Science Foundation of China(52222409)
National Natural Science Foundation of China(52074132)
National Natural Science Foundation of China(U19A2084)
National Natural Science Foundation of China(U22A20109)
National Key Research and Development Program(2022YFE0122000)
Interdisciplinary Integration and Innovation Project of JLU(JLUXKJC2021ZZ08)
Fundamental Research Funds for the Central Universities,JLU()
NETL
NSTL
万方数据