铸造工艺参数和细化剂对K4169高温合金铸态组织的影响Ⅰ.晶粒组织及晶粒细化机理

研究了K4169高温合金在各种工艺条件下及向熔体中加入复合细化剂时的晶粒组织。结果表明，降低浇注温度和加入复合细化剂可以明显细化冷凝后基体的晶粒和提高铸件断面等轴晶的比例。在通常的浇注温度1400℃下加入复合细化剂。对合金熔体进行或不进行过热处理时，可使圆柱锭的晶粒分别细化至ASTM1.7级和ASTM3.2级；断面等轴晶的比例分别达96％和99％以上。当浇注温度为1420℃、加入复合细化剂并对合金熔体进行过热处理时。可使圆柱锭晶粒细化至ASTM M10.5级，断面等轴晶的比例达90％以上。提出了晶粒细化的机理并对晶粒细化后断面等轴晶比例增大的现象进行了分析。

EFFECTS OF FOUNDRY VARIABLES AND REFINERS ON CAST STRUCTURES OF SUPERALLOY K4169 Ⅰ.Grain Structures and Grain Refinement Mechanisms

Grain structures of cast superalloy K4169 have been investigated under various casting conditions together with the addition of mixed refiners. It is found that lowering pouring temperature and adding mixed refiners to the melt can lead to grain refinement of matrix and improve the proportion of equiaxed grains at cross-section. While adding mixed refiners, at a conventional pouring temperature of 1400 . the average size of equiaxed grains (r) could be refined to the order of ASTM 1.7, the proportion of equiaxed grains at traverse cross-section (p) could be improved from 56% to 96% with the melt superheating treatment. Furthermore, r could be refined to 0.1158 mm, i.e. to ASTM 3.2, and p has been increased to 99% without the melt superheating treatment. When the pouring temperature is 1420. r has been refined to the order of ASTM M10.5, and p could be increased to 90% by the addition of mixed refiners and the melt superheating treatment. Additionally, the mechanisms of grain refinement were proposed and the phenomenon that p was improved after grain refinement has been analyzed.