【作者】 赵彦杰； 周剑秋；

【Author】 Zhao Yanjie;Zhou Jianqiu;Department of Mechanical and Power Engineering,Nanjing Tech University;Wuhan Institute of Technology,School of Mechanical and Electrical Engineering;

【机构】 南京工业大学机械与动力工程学院； 武汉工程大学机电工程学院；

【摘要】 纳米晶体材料由于其特殊的微观结构使得其具有常规粗晶材料所不具备的一系列优异的力学性能,如较高的屈服强度、硬度及良好的耐磨性能。然而其特殊的微观结构和变形机理也使得材料内部的损伤演化过程与常规粗晶材料有很大不同。本文在充分理解常规粗晶材料中损伤演化过程以及纳米晶体材料变形机理的基础上以铜基纳米晶镍涂层为研究对象,在室温下对涂层进行了拉伸力学性能测试及划痕测试,利用3D数字图像相关法及场发射扫描电镜分析了纳米晶镍涂层试样拉伸过程中涂层的断裂机理及涂层和基体界面失效的情况。研究结果表明:随应变率的增加,试样的延伸率和强度增大。纳米晶镍涂层的断裂主要是由于纳米晶镍涂层中位于界面附近的纳米尺度的晶界裂纹的萌生,并沿着晶界不断地向涂层表面扩展引起的。此外,通过划痕测试得到了纳米晶镍涂层和基体发生失效时的临界应力及失效方式。更多还原

【Abstract】 Nanocrystalline materials show ultra-high yield strengths,superior wear resistance,and enhanced hardness due to their unique microstructure.However,the unique microstructure and plastic deformation mechanism in nanocrystalline materials lead to the different damage evolution process between nanocrystalline materials and coarse-grained materials.On the basis of completely understanding on the damage evolution process in coarse-grained materials as well as the unique deformation mechanism of nanocrystalline materials.The nanocrystalline Ni coating is characterized under the uniaxial tensile tests,the evolution of strain,nucleation and propagation of crack,fracture process and failure of interface between coating and substrate were studied using the 3 D digital image correlation(DIC)as well as the field emission scanning electron microscope(FESEM).The results show that strain rate has an effect on the ductility and strength of the sample at room temperature,and the ductility and strength increase with increasing strain rate.The fracture of coating is caused by the nucleation and propagation of intergranular nano-sized cracks near the interface.Also,the interface failure between coating and substrate was studied using scratch test.更多还原