Abstract: Al-80%TiC and Al-50%TiC grain refiners were directly synthesized by self-propagating high-temperature synthesis (SHS) technology. The phase components and microstructures of the synthesized grain refiners were examined by XRD and SEM, and their grain refining performances for commercially pure aluminum were also evaluated and compared with commonly used Al-5Ti-1B grain refiner. The results show that the SHS grain refiners consist of TiC and α-(Al), and that the size and distribution of TiC particles have significant influence on the grain refining properties of the SHS grain refiners. Al-80%TiC has poor grain refining effect because of coarser size (2～5μm) and agglomeration of the synthesized TiC particles, whereas Al-50%TiC exhibits higher grain refining performance than Al-5Ti-1B . The addition of SHS Al-50%TiC grain refiner to the molten aluminum in the amount of 0.1% might transform the structure of the solidified samples from coarse columnar grains to fine equiaxed grains (average grain size 120μm), and this grain refining effect could be maintained for 90min at 1003K. SEM and TEM examinations show that submicron (0.4～0.9μm) TiC particles in SHS Al-50%TiC grain refiner exhibit high thermodynamic stability in liquid aluminum, thereby affording the grain refiner excellent grain refining performance and high resistance to grain refining fading.
SHS of Al-TiC grain refiners and their grain refining performances for commercially pure aluminum
Abstract：
Al-80%TiC and Al-50%TiC grain refiners were directly synthesized by self-propagating high-temperature synthesis (SHS) technology. The phase components and microstructures of the synthesized grain refiners were examined by XRD and SEM, and their grain refining performances for commercially pure aluminum were also evaluated and compared with commonly used Al-5Ti-1B grain refiner. The results show that the SHS grain refiners consist of TiC and α- (Al) , and that the size and distribution of TiC particles have significant influence on the grain refining properties of the SHS grain refiners. Al-80%TiC has poor grain refining effect because of coarser size (2～5 μm) and agglomeration of the synthesized TiC particles, whereas Al-50%TiC exhibits higher grain refining performance than Al-5Ti-1B . The addition of SHS Al-50%TiC grain refiner to the molten aluminum in the amount of 0.1% might transform the structure of the solidified samples from coarse columnar grains to fine equiaxed grains (average grain size 120 μm) , and this grain refining effect could be maintained for 90 min at 1 003 K. SEM and TEM examinations show that submicron (0.4～0.9 μm) TiC particles in SHS Al-50%TiC grain refiner exhibit high thermodynamic stability in liquid aluminum, thereby affording the grain refiner excellent grain refining performance and high resistance to grain refining fading.
Fig.4 Macrographs of solidified Al samples refined with different grain refiners (refining temperature 1 003 K, holding time 3 min)
图5 细化剂的加入量对试样晶粒尺寸的影响
Fig.5 Effects of additions of grain refiners on average grain sizes of solidified samples (refining temperature 1 003 K, holding time 3 min)
图6 铝液的保温时间对试样的晶粒尺寸的影响
Fig.6 Effects of holding time of liquid aluminum on average grain size of solidified samples refined with different grain refiners (refining temperature 1 003 K)
Fig.7 TEM micrographs of solidified Al samples refined with different grain refiners (refining temperature 1 003 K, holding time 90 min) (a) —Al-5Ti-1B; (b) —SHS Al-50TiC
