生长速率对定向凝固NiAl-43V过共晶合金组织演变和室温断裂韧性的影响  

Effect of Growth Rate on Microstructure Evolution and Room Temperature Fracture Toughness of Directionally Solidified NiAl-43V Hypereutectic Alloy

作　　者：徐鹏飞 张建飞[2] 陈林[2] 金自力[2] 任慧平 Xu Pengfei;Zhang Jianfei;Chen Lin;Jin Zili;Ren Huiping(Inner Mongolia University of Science and Technology,Baotou 014010,China;Key Laboratory of Advanced Metal Materials,Inner Mongolia,Baotou 014010,China)

机构地区：[1]内蒙古科技大学材料与冶金学院,内蒙古包头014010 [2]内蒙古科技大学,内蒙古包头014010 [3]内蒙古新金属材料重点实验室,内蒙古包头014010

出　　处：《稀有金属材料与工程》2020年第4期1415-1421,共7页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(51564041);内蒙古自然科学基金(2018MS05028)。

摘　　要：采用高温度梯度液态金属冷却技术(LMC)制备了Ni-28.5Al-43V(at%)过共晶合金,利用光学显微镜(OM)、扫描电镜(SEM)和三点弯曲(3PB)测试对合金的组织演变和断裂韧性进行了研究。在温度梯度GL=310 K/cm,生长速率V=6~150μm/s的实验条件下,NiAl-43V的凝固组织均为初生V枝晶+共晶组织(NiAl片层+V片层)。硬度测试表明初生V枝晶的硬度高于共晶相的硬度。断裂韧性测试表明NiAl-43V过共晶合金最大室温断裂韧性相比NiAl合金提高了4倍。随着生长速率的增大,室温断裂韧性从6μm/s的22.679 MPa·m^1/2逐渐下降到150μm/s的18.422 MPa·m^1/2。这是因为生长速率增大产生的细晶强化效应弱于初生V枝晶和胞间区域的增加对断裂韧性产生的不良影响。合金的断口形貌分析表明合金断裂为准解理断裂,在裂纹扩展中裂纹钝化、裂纹再形核、裂纹偏转、界面剥离、裂纹桥接和微裂纹键合韧化机制对提高NiAl-43V合金的室温断裂韧性做出了贡献。初生V枝晶的析出一定程度降低了合金的断裂韧性。The Ni-28.5Al-43V(at%)hypereutectic alloy was prepared by liquid metal cooling technology(LMC).The microstructure evolution and mechanical properties of the alloy were investigated by optical microscopy(OM),scanning electron microscopy(SEM)and three-point bending(3PB)test.Under the experimental conditions(temperature gradient GL=310 K/cm,growth rate V=6~150μm/s),the results show that the steady-state growth microstructure of NiAl-43V is composed of primary V dendrites and eutectic structure(NiAl lamellar+V lamellar).Hardness test shows that the hardness of primary V dendrites is higher than that of eutectic phase.3 PB test shows that the maximum room temperature fracture toughness(RTFT)of NiAl-43V hypereutectic alloy is four times higher than that of NiAl alloy.The RTFT decreases from 22.679 MPa·m^1/2 at 6μm/s to 18.422 MPa·m^1/2 at 150μm/s as the growth rate increases.The reason is that the fine-grained strengthening effect caused by the increase of growth rate is weaker than the adverse effect of increased primary V dendrites and inter-cell regions on fracture toughness.Fracture morphology analysis of alloys indicates that alloy fracture is quasi-cleavage fracture.Crack blunting,crack renucleation,crack deflection,interfacial debonding,crack bridging and linkage of microcrack toughening mechanism contribute to the improvement of room temperature fracture toughness of NiAl-43V alloy in crack propagation.The precipitation of primary V dendrites reduces the fracture toughness of the alloy.

关 键 词：NiAl-V过共晶 凝固组织 室温断裂韧性 韧化机制 

分 类 号：TG113.12[金属学及工艺—物理冶金] TG113.254[金属学及工艺—金属学]