利用5kW CW CO2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106K/m, 速度可高达24.1mm/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=1.25v-0.61b, λmin=4.47v-0.52b, λ-=9.09v-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.
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