超高温度梯度快速定向凝固的Cu-Mn合金胞晶间距  

Cellular spacing of Cu-Mn alloy under ultrahigh temperature gradient and rapid directional solidification

作　　者：杨森[1] 黄卫东[2] 张庆茂[1] 刘文今[1] 周尧和[2] 

机构地区：[1]清华大学机械系,北京100084 [2]西北工业大学凝固技术国家重点实验室,西安710072

出　　处：《中国有色金属学报》2001年第z2期243-247,共5页The Chinese Journal of Nonferrous Metals

基　　金：国家自然科学基金资助项目 (5 97710 5 4);清华大学 985重点资助项目

摘　　要：利用 5kWCWCO2 激光器对Cu 31.4 %Mn合金进行了一系列表面重熔实验 ,就激光束扫描速度对重熔区微观组织生长方向的影响和超高温度梯度快速定向凝固条件下胞晶间距选择规律进行了研究。实验结果表明 :熔池中微观组织的生长方向强烈地受激光工艺参数 (激光输出功率和扫描速度 )的影响。通过采用本实验的工艺 ,实现了与Bridgman法类似的超高温度梯度快速定向凝固 ,其温度梯度可高达10 6K/m ,速度可高达 2 4 .1mm/s。Cu 31.4 %Mn在超高温度梯度快速凝固条件下的胞晶间距存在一个分布范围。随生长速度的增大 ,胞晶间距减小。胞晶间距与生长速度的关系为 :λmax=1.2 5v-0 .61b ,λmin=4 .4 7v-0 .52b ,λ— =9.0 9v-0 .62b 。实验结果与快速凝固条件下枝晶生长模型 (Hunt Lu模型 )吻合。Detailed laser surface remelting experiments of Cu 31.4% Mn alloy on a 5?kW CW CO 2 laser were carried out to study the effects of processing parameters (scanning velocity, laser output power) on the growth direction of microstructure in the molten pool and cellular spacing selection under ultrahigh temperature gradient and rapid directional solidification conditions. The experimental results show that growth direction of microstructure is strongly affected by laser processing parameters. Ultra high temperature gradient directional solidification can be realized on the surface of samples during laser surface remelting by controlling laser processing parameters, whose temperature gradient can reach 10 6 K/m and growth velocity can reach 24.1?mm/s, and the solidification microstructure grows along the laser beam scanning direction. There exists a distribution range in cellular spacing under laser rapid solidification condition, the average spacing decrease with increase of the growth rate. The maximum, λ max , minimum, λ min , and average primary spacing, λ- , as functions of growth rate v b, can be given by λ max = 1.25 ? v -0.61 b , λ min = 4.47 ? v -0.52 b , λ- = 9.09 ? v -0.62 b , respectively. The experimental results are compared with the current Hunt Lu model for rapid cellular/dendritic growth, and a good agreement is found.

关 键 词：激光表面熔凝 超高温度梯度 定向凝固 胞晶间距 

分 类 号：TG111[金属学及工艺—物理冶金]