The Grain Structure of Castings

铸件的晶粒结构

• 批准号: 9521875
• 负责人: Angus Hellawell
• 金额: $ 15.99万
• 依托单位: Michigan Technological University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-01-01 至 1998-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9521875&HistoricalAwards=false
• 关键词: Grain; Structure; Castings

9521875 Hellawell This two-year renewal provides for completion of research on the development of equiaxed grains in metal castings. The initial source for the grain solidification is thought to be dendrite fragments that have become detached within the earlier mushy region of the casting. The fragments are transported out into the bulk liquid by thermo-solutal convection. Surviving fragments grow, sink, and eventually block columnar grains. The steps in modeling the process have been identified and analyzed in some detail, and it is recognized that the conditions that promote dendrite arm detachment are associated with transient growth conditions. These conditions mirror those in a casting, where columnar dendritic growth front is decelerating continuously and the temperature gradient is falling simultaneously. This critical step in the process is examined analytically and experimentally using transparent analogues and selected metal alloys. %%% This topic addresses a major gap in understanding the development of the microstructure of alloy castings. This complex process should be clarified by the experimental and theoretical work proposed. ***

小行星9521875 这项为期两年的更新规定完成对金属铸件中等轴晶粒发展的研究。 晶粒凝固的初始来源被认为是在铸件的早期糊状区域内已经分离的枝晶碎片。 碎片被运送到 散装 液体通过热溶质对流。 残存的碎片生长、下沉，并最终阻塞柱状晶粒。 在建模的过程中的步骤已被确定和分析的一些细节，它是公认的，促进枝晶臂脱离的条件与瞬态生长条件。 这些条件反映了铸件中的条件， 柱状 树突状 增长 前 是 连续减速 和 的 温度 梯度 是 同时下降。 这个过程中的关键步骤进行了检查分析和实验使用透明的类似物和选定的金属合金。 本主题解决了在理解合金铸件微观结构发展方面的一个主要空白。 这一复杂的过程应通过所提出的实验和理论工作加以阐明。 ***