Laves相Cr_2Nb-20Ti合金定向凝固组织与取向生长  

Microstructure Evolution and Preferred Growth Direction of Laves Phase Cr_2Nb-20Ti Alloy during Directional Solidification

作　　者：薛云龙[1] 李双明[1] 李克伟[1] 张婷[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

出　　处：《稀有金属材料与工程》2015年第2期375-380,共6页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(51074127)

摘　　要：考察了Cr2Nb-20Ti(原子分数,下同)合金在5,10,20,100μm/s 4种定向凝固速率下的组织演变,研究结果表明:各凝固速率下合金的组织均由C15-Cr2Nb枝晶和枝晶间β-Ti构成,高温相β-Ti的形成是由Cr起到稳定化作用所致。随着凝固速率的增加,C15-Cr2Nb板条枝晶逐渐分裂,形貌由粗大板条转变为不规则多边形,同时凝固速率越大,扰动波长越小,枝晶组织越细,枝晶生长方向越偏向择优取向。实验中C15-Cr2Nb的择优生长晶面为(220),因该晶面有较大的裸露键能,生长时处于优势而淘汰其它生长晶面。The Cr2Nb-20Ti（atomic fraction） prepared by directional solidification with the withdrawal rates of 5, 10, 20, 100 μm/s were investigated to understand the microstructure evolution of the Laves phase Cr2Nb/Ti alloy. OM, XRD, and SEM apparatus were employed to determine the solidified phases and microstructure. The results indicate that the microstructures of directionally solidified Cr2Nb-20 Ti alloy are all consisted of C15-Cr2 Nb dendrite and interdendritic β-Ti. The formation of metastable β-Ti instead of stable α-Ti is induced by the stabilization of Cr element. With the increase in withdrawal rate and perturbation at the liquid/solid interface, the C15-Cr2 Nb dendrites are refined and the dendritic morphology evolves from the petal-like pattern at 5 μm/s to the polygon-like pattern at 100 μm/s;simultaneously, the growth direction of the C15-Cr2 Nb dendrite gradually deviates from the heat flow direction and transits to the preferred growth direction. From the XRD experimental result, it shows that the C15-Cr2 Nb dendrite exhibits the（220） preferred growth plane due to the fact that the plane（220） has the maximal bare bond energy, leading to the fast growth kinetic and elimination of other growth planes.

关 键 词：三元合金 定向凝固 组织演变 Cr2Nb枝晶 择优取向 

分 类 号：TG144[一般工业技术—材料科学与工程]