论文部分内容阅读
应用光学显微镜及电子显微镜对18 CrNiWA钢经不同温度奥氏体化及等温处理所得的组织进行了研究,发现该钢在整个中温转变温度范围内可同时存在块状铁素体及板条状铁素体(即贝氏体铁素体),这是两种不同类型的铁素体组织。提高等温温度或降低奥氏体化温度有利于块状铁素体形成;反之有利于贝氏体铁素体转变;并得出这种中温块状铁素体具有以下的相变特征:(1)无浮凸效应。(2)三维形态呈等抽状或不规则的外形,它是由高密度位错的块状亚结构所组成。(3)可同时在晶内和晶界形核。(4)能跨越原晶界或孪晶界而生长,并仍保留原奥氏体晶界的痕迹,但不继承孪晶组织。(5)形成温度较高时,得到无碳化物析出的块状铁素体包围着的岛状组织,后者含碳量远高于原始的平均成份;形成温度较低时,在块状铁素体中可析出单向或多向分布的碳化物。上述(1)～(4)四种相变特征与块状转变相类似。我们初步认为这种中温块状铁素体的形成是铁原子短程扩散的γ→α转变与碳原子长程扩散的综合结果。
The microstructure and microstructure of 18 CrNiWA steel after austenitizing and isothermal treatment at different temperatures were investigated by optical microscopy and electron microscopy. It was found that the microstructure of the 18 CrNiWA steel coexisted with massive ferrite and slab-like iron The body (ie, bainitic ferrite), which is two different types of ferrite. Increasing the isothermal temperature or decreasing the austenitizing temperature is favorable for the formation of massive ferrite; on the contrary, it is conducive to the transformation of bainitic ferrite; and this intermediate-temperature massive ferrite has the following phase transition characteristics: (1 No embossing effect. (2) The three-dimensional shape is isometric or irregular in shape, which is composed of massive sub-structures of high-density dislocations. (3) Both in the grain and grain boundary nucleation. (4) can grow across the original grain boundary or twin boundaries and still retain the traces of the original austenite grain boundaries, but do not inherit twins. (5) When the formation temperature is higher, the island-like structure surrounded by massive ferrite without carbide precipitation is obtained, the carbon content of which is much higher than the original average composition; when the formation temperature is low, The body can precipitate unidirectional or multi-directional distribution of carbides. The above four kinds of phase transition features (1) to (4) are similar to the bulk transition. We initially consider that the formation of this intermediate-temperature massive ferrite is the result of the γ → α transition of short-range iron atoms and the long-range diffusion of carbon atoms.