Hengcheng Liao
材料科学技术（英文）
The influence of addition of boron (B) on eutectic solidification in a near-eutectic Al-13.0%Si alloy modified with strontium (Sr) was investigated using thermal analysis and macro/microstructure observation. Addition of B in the Sr-modified alloy leads to a considerable increase in nucleation temperature (TN, the minimum temperature prior to recalescence (TM) and growth temperature (TG). In the Sr-modified alloy, nucleation of eutectic might originate at the heterogeneous sites on the mold wall or in the melt near the wall, and eutectic solidification proceeds gradually towards the center, controlled by undercooling of melt. However, with addition of B in the Sr-modified alloy, undercooling required for eutectic nucleation became small, and hence eutectic solidification might occur almost simultaneously within whole casting, controlled by amount of heterogeneous sites. With excessive addition of B in the Sr-modified alloy, nucleation of eutectic grains was explosive within the whole casting and the power of Sr on eutectic solidification was completely poisoned.
关键词:
Al-Si alloys
王长久
,
董蒙
,
刘铁
,
高鹏飞
,
牛书秀
,
苑轶
材料导报
doi:10.11896/j.issn.1005-023X.2016.02.021
采用超导强磁场装置研究了磁场强度对有、无细化剂颗粒Al-7％Si(质量分数)合金凝固组织的作用效果.研究发现,施加强磁场使无细化剂颗粒合金中的初生α-Al枝晶转变为发达枝晶形貌,二次枝晶生长充分,三次枝晶分支明显,枝晶尖端清晰可见;晶粒细化,且枝晶主轴与磁场方向呈30°规则排列.施加强磁场后初生α-Al枝晶数量和Si在α-Al中的溶解度都有少量增加.强磁场抑制添加细化剂合金熔体中的对流,加剧了Ti的重力偏析,使初生α-Al相出现明显枝晶化趋势,方向性增强,枝晶臂粗化明显.
关键词:
强磁场
,
Al-Si合金
,
凝固
,
枝晶
