研究了激光重熔工艺参数对三种不同成分的Cu-Mn合金重熔区微观组织生长方向的影响.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)和合金成分的影响.通过选择合适的工艺参数,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106 K/m,速度可高达24 mm/s.利用激光表面熔凝技术实现超高温度梯度快速定向凝固的关键在于:1) 在激光熔池内获得与激光扫描速度方向一致的温度梯度;2) 根据合金凝固特性选择适当的激光工艺参数以获得胞晶组织.

Detailed laser surface remelting experiments of three kinds of Cu Mn alloys were carried out to study the effects of technology parameters (scanning velocity, laser output power) on the growth direction of microstructure in the molten pool. The experimental results show that growth direction of microstructure are strongly affected by laser technology parameters and alloy composition. Ultra high temperature gradient directional solidification can be realized on the surface of samples by laser surface remelting, whose temperature gradient can reach 10 6 K/m and growth velocity can reach 24 mm/s, and the solidification microstructure grows along the laser beam scanning direction. In order to obtain ultra high temperature gradient and rapid directional solidification with laser surface remelting, the key problems are: 1) to ensure temperature gradient in the molten pool parallel to laser beam scanning direction; 2) to select adequate technology parameters to ensure cellular growth.