Microstructure of Al-Cu Alloy in Rapid Solidification by CO_2 Laser

CO_2激光快速凝固Al-Cu合金的显微组织

• 批准号: 06650832
• 负责人: MIYATA Yasunori
• 金额: $ 1.09万
• 依托单位: Nagaoka University of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650832/
• 关键词: rapid solidification; laser; absolute stability; alloy; dendrite; cellular structure; エネルギー吸収率; 冷却速度; ミクロ組織; セル界面; 絶対安定

New microstructure of alloy is expected to be in rapid solidification, when the melt solidify in its growth rate close to the the absolute stability limit. This limiting growth rate is reached if the growth rate approaches to the speed of diffusion of the solute. The purpose of this work is to study the relation between the microstructure and solidification condition in rapid solidification of Al-Cu alloy.Low solute Al-Cu alloy is used in this experiment. It makes easy to realize the absolute stability condition and it also makes easy to cbserve the microstructure, because low colute concentration will result larger microstructure of alloy. High power CO_2 laser (Max. 6KW) is used to melt and solidify rapidly, and rapid solidification with a few meter per second is realized. The temperature distribution in the melt is studied by numerical analysis MARC.In terms of this distribution the temperature gradient and the growth rate at the solid-liquid interface is obtained.Cellular microstructure is found in Al-0.5 mol%Cu alloy, which is solidified with growth rate 1.7 m/sec. This growth rate is very close to the absolutely stable growth rate of this alloy, which is predicted to be 2.4m/sec by the pertubative theory. Other alloys with thjeir solute concentration 1.0 and 4.5mol%Cu alloy do not show cellular structure but dendritic microstructure. The diameter of the primary stem decreases with growth rate by power-1/2.

当熔体在其生长速率接近绝对稳定极限时，合金的新组织有望处于快速凝固状态。如果生长速度接近溶质扩散的速度，就达到了这个极限生长速度。本工作的目的是研究Al-Cu合金快速凝固过程中微观组织与凝固条件之间的关系。它使绝对稳定条件的实现变得容易，也使组织保存变得容易，因为较低的溶质浓度会产生较大的显微组织。高功率CO_2激光器(最大6kW)快速熔凝，实现了每秒几米的快速凝固。利用数值分析软件MARC研究了熔体内的温度分布，得到了固液界面的温度梯度和生长速率。Al-0.5mol%Cu合金以1.7m/s的生长速率凝固后，观察到了胞状组织。这一生长速度非常接近该合金的绝对稳定生长速度，微扰理论预测的绝对稳定生长速度为2.4m/s。溶质浓度为1.0和4.5mol%的铜合金不再形成胞状组织，而是枝晶组织。初生茎粗随生长速度呈1/2次方减小。