生长速率对NiAl-7.8Mo亚共晶合金定向凝固组织及界面形态的影响  

Effect of Growth Rate on Microstructure and Interface Morphology of Directionally Solidified NiAl-7.8Mo Hypoeutectic Alloy

作　　者：张建飞[1,2] 沈军[1] 商昭[1] 冯周荣[1] 傅恒志[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072 [2]内蒙古科技大学,内蒙古包头014010

出　　处：《稀有金属材料与工程》2013年第2期263-267,共5页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(51074128);航空科学基金(2007ZF53067);陕西省自然科学基金(2010JM6002)

摘　　要：采用高温度梯度定向凝固装置制备了NiAl-7.8Mo亚共晶合金,系统研究了生长速率对合金凝固时界面形态、枝晶生长及初生相析出的影响。随生长速率的增大,固液界面依次呈现平、胞枝、枝的形貌转变,初生β相的一次枝晶间距λ1在胞晶生长阶段逐渐增大,而在枝晶生长阶段λ1又逐渐减小;二次枝晶间距λ2随生长速率的增加一直减小。初生β相的析出量随生长速率的增加而增加。分析结果表明:生长速率增加导致熔体过冷度增加,使得NiAl初生相形核率增加,最终导致初生β相的析出量随生长速率的增加而增加。The alloy with composition Ni-45.61Al-7.8Mo （at%） has been directionally solidified by liquid metal cooling （LMC） process. The effect of growth rate on the solidified microstructure such as interface morphology, dendrite growth and primary β phase precipitation, was experimentally investigated. The interface morphology of the β phase undergoes the evolution from plane front, cellular, thick dendrite to thin dendrite with increasing of growth rate for a given temperature gradient. The first dendrite spacing λ1 of the primary β phase increases gradually during the cellular growth, and decreases during the dendrite growth, while the second dendrite spacing λ2 decreases with increasing of the growth rate. The amount of primary β phase increases with the growth rate. And the analysis results show that the varieties of nucleation rate of NiAl caused by melt undercooling variation with different growth rates are responsible for the phenomenon.

关 键 词：定向凝固 NiAl-Mo合金 生长速率 界面形态 

分 类 号：TG146.15[一般工业技术—材料科学与工程]