定向凝固NiAl-9Mo共晶合金的凝固组织特性

采用液态金属冷却法在恒定温度梯度GL=334 K/cm，大生长速率范围内（2~300μm/s）对Ni-45.5Al-9Mo （摩尔分数，%）共晶合金进行定向凝固制备。研究生长速率（v）对纤维间距（λ）、纤维直径（d）和纤维体积分数的影响。在实验中发现平界面和胞界面两类共晶生长界面。在平界面和胞界面组织中，生长速率（v）与纤维间距（λ）和纤维直径（d）的关系经回归分析分别为：λv1/2=5.90μm·μm1/2·s1/2和 dv1/2=2.18μm·μm1/2·s1/2。Mo纤维的体积分数可在一定的范围内随生长速率进行调整，这是由生长过程中界面前沿过冷度的增加及共晶组织中各组成相的生长特性引起的。

Directional solidification and characterization of NiAl-9Mo eutectic alloy

Ni-45.5Al-9Mo （mole fraction,%） alloy was directionally solidified with a constant temperature gradient （GL=334 K/cm） and growth rates ranging from 2 to 300 μm/s using a Bridgman type crystal growing facility with liquid metal cooling （LMC） technique. The effect of growth rate （v） on the solidified microstructures such as rod spacing （λ）, rod size （d） and rod volume fraction was experimentally investigated. Two types of the solidified interfaces, planar and cellular, were identified. On the condition of both planar and cellular eutectic microstructures, the relationships between λ, d and v were given as： λv1/2=5.90 μm·μm1/2·s1/2 and dv1/2=2.18μm·μm1/2·s1/2, respectively. It was observed that the volume fraction of Mo phase could be adjusted in a certain range. The variation of phase volume fraction was attributed to undercooling increase and the growth characteristics of the individual constituent phases during the eutectic growth.