【作者】 张凯；

【导师】 孔毅；

【作者基本信息】 中南大学 ， 材料科学与工程， 2014， 硕士

【摘要】 摘要：本文以WC-40Vol.％Ni3Al合金和WC-40Vol.％(Ni3A1+Co)合金为研究对象,对比WC-40Vol.％Co合金,通过X射线衍射测试、电子探针显微分析、选区电子衍射分析、高分辨透射电子显微分析及晶体间取向关系矩阵计算,详细研究了这两个含Ni3Al合金的微观组织结构,并结合所测微结构探讨了造成合金宏观力学性能差异的可能原因。研究结果表明：(a)WC-40Vol.％Ni3Al合金的粘结相为含少量W、C固溶原子的Ni3Al相,WC与Ni3A1的取向关系虽具有一定的随机性,但在选区电子衍射和高分辨电子显微图像中均发现了一组优势取向关系,可以表述为：[100]WC//[110]Ni3Al,(001)WC//(001)Ni3A1.在该取向下,(100)WC//(110)Ni3AI,这与XRD衍射中可能具有相干性的一组晶面完全吻合。WC-40Vol.％(Ni3Al+Co)合金的粘结相由γ’((Ni1-xCox)3A1)相和γ((Co1-xNix))相共同组成,γ’相呈方块状,边长约100nm。通过选区电子衍射发现了一组WC与粘结相的取向关系,可以表述为：[011]WC//[112]binder,(122)WC//(220)binder.(b)WC颗粒在Ni3Al中边缘圆钝,远不同于其在纯Co中的刻面状,但WC颗粒在Ni3Al中更为细小,在Co中分布得更均匀。而WC-40Vol.％(Ni3A1+Co)合金中同时存在具有圆钝状形貌的和刻面状形貌的WC颗粒。WC/Ni3Al界面的成分梯度大于WC/CO界面,界面过渡层较薄,而WC/(Ni3Al+Co)界面的成分梯度介于两者之间。(c)WC-40Vol.％Ni3Al合金的硬度高于WC-40Vol.％Co合金,但其横断强度和断裂韧性均小于WC-40Vol.％Co合金,而WC-40Vol.％(Ni3Al+Co)合金的硬度和横向断裂强度均高于其余两合金。图30幅,表13个,参考文献71篇更多还原

【Abstract】 Abstract:Two types of cemented carbides, WC-40vol.%Ni3Al and WC-40vol.%(N13AI+Co), were studied in the present work and the traditional WC-40vol.%Co composites were examined for comparison. Experimental methods including X-ray diffraction (XRD), electron probe microanalysis, selected area electron diffraction (SAED) its simulation, high resolution transmission electron microscopy (HRTEM), and matrix calculation of interfacial orientations were employed to investigate the microstructures of the two metals containing Ni3Al. The possible reasons for the difference in the mechanical properties between the two composites were discussed based on the microstructural results. The conclusions are listed below:The binder phase in the WC-40vol.%Ni3Al composites is the Ni3Al compound with slight solution of W and C. Although WC grains and Ni3Al match each other mainly in random relationships, a preferential orientation relationship between them was repetitively found by SEAD and HRTEM observations. This orientation relation can be descripted as:[100]WC//[110]Ni3Al,(001)wc//(001)Ni3Al, under which, the derived relations (100)WC//(110) Ni3Al consists well with a set of probably coherent planes that were detected from XRD measurements.The binder phase in the WC-40vol.%(Ni3Al+Co) composites was found to be the mixture of y1((Ni1-xCox)3Al) and y ((Co1-xNix)). The ordered γ’ with cubic morphology was dispersed in the disordered y phase, the size of γ’ is about100nm. A set of orientation relationship between WC grains and the binder phase, which can be described as [011]WC//[112]binder,(122)wc//(220)binder, was found via SAED.The edge of WC grains in the WC-40vol.%Ni3Al alloy was found to be round and blunt, which is quite different from those sharp edges found in the WC-40vol.%Co composites; the WC grains in the alloys containing Ni3Al were found to be finer compared with those that only consist of Co; WC grains are more uniformly distributed in the Co binder phases than in the other two. Both round and sharp edges of the WC grains can be observed in the WC-40vol.%(Ni3Al+Co) alloys, and the size of these grains fall in between of the other two alloys. The compositional gradient at the WC/Ni3Al interfaces were larger and resultant transition layers are thinner than those at the WC/Co interfaces, and those of the WC-40vol.%(Ni3Al+Co) alloy again fall in between of the two alloy above.The hardness of the WC-40vol.%Ni3Al composites is higher but its transverse rupture strength and fracture toughness are lower compared to the WC-40vol.%Co alloy. The transverse rupture strength and fracture toughness of the WC-40vol.%(Ni3Al+Co) alloy are the highest among the three alloys.更多还原