含镍合金球墨铸铁的拉伸断裂行为分析

用扫描电镜研究了含镍合金球铁的拉伸断口特性，根据其延伸率可判断其断裂属于脆性断裂，微观断裂机理是准解理加少部分剪断（有韧窝），韧窝主要分布在石墨球周围的基体中；贝氏体或马氏体针片的细化程度和残奥对主裂纹的扩展有较大影响。用层磨断口及深腐蚀技术，研究了二次裂纹的起裂特点，发现了二次裂纹的萌生有三种方式，用振动汽蚀机测定了合金球铁的抗汽蚀性，指出贝氏体或马氏体针愈细小，分布愈散乱，其抗汽蚀性愈好。还用ＳＥＭ分析了汽蚀裂纹的起裂和扩展特性。

Analysis of Tensile Fracture of Alloying Ductile Cast Iron Containing Ni and Its Cavitation Erosion Resistance

The fractured surface of the alloying ductile cast iron containing elements of Ni,Mo,Cu,B are investigated by using SEM,The fracture of the alloying ductile irons be-longes to brittle fracture according to their elongations. It is found that the microsfracture isquasi-cleavage as the majority shear fracture as the minority(the dimples are existed).Thedimples are distributed in matrix near the nodular graphite. The fine degree of bainitic ormartenitic needles and remained austenite greatly affect the propagation of main crack.Thefracture characteristics of secondary crack is investigated by using the technique of polishingalayer of fractured surface and deep corrosion. The three modes of inoculating secondarycrack are found. The cavitation erosion of several kinds of alloying nodular iron is measuredby using vibration cavitation simulating device. It is found that the finer the needles the bai-nite or martensite are,the better the cavitation erosion of alloying nodular iron is. The prop-erties of inoculation and propagation of cavitation crack is also observed by SEM.