一种新的断口金相技术被用来测定低循环疲劳试验断口,材料取自蒸汽轮机转子的镗孔区。1950年以来,发现大量蒸汽轮机的转子带有内部缺陷,包括夹杂、显微收缩空穴等。在研究高应力低循环疲劳状态下裂纹的起始和扩展方面,逐渐发展了这种有价值的加热着色断口金相技术。它可以根据断口的不同色区,明确地判断出各种断裂机理。 收缩缺陷保持银白色,疲劳条带为综色,塑性断口为蓝色,解理面为金黄至紫色。据此可以推断出转子试样的裂纹起始和扩展过程,并与扫描电镜断口照片对比加以证实。此外还可以测定裂纹稳定增长和裂纹过载区的相对缺陷面积,并与金相试片上缺陷面积率比较。 这种着色断口金相的原理如下。当一块金属在空气中加热时,形成氧化物的厚度取决于氧化速率、温 A new fracture metallurgical technique was used to determine the low-cycle fatigue test fracture taken from the borehole area of ​​the steam turbine rotor. Since 1950, a large number of steam turbine rotors have been found to have internal defects including inclusions, microscopic shrinkage cavities and the like. In the study of the onset and propagation of cracks under high-stress, low-cycle fatigue, this valuable technique of hot-colored fracture metallurgy was developed. It can be based on the fracture of the different color areas, clearly determine the fracture mechanism. Shrinkage defects remain silver, fatigue bands for synthetic color, plastic fracture blue, cleavage surface is golden to purple. From this it can be deduced that the crack initiation and propagation process of the rotor specimen is confirmed by comparison with the scanning electron microscope fracture photograph. In addition, the relative crack growth area and crack overburden area relative flaw area can be measured and compared with the defect area ratio on the metallographic specimen. The principle of this colored fracture fracture is as follows. When a piece of metal is heated in the air, the thickness of the oxide formed depends on the oxidation rate, the temperature