等温淬火球铁的微观组织与力学性能

Microstructure and Mechanical Properties of Isothermally-Quenched (Austempered) Ductile Iron

等温淬火球铁的显微组织由奥氏体加针状铁素体的混合组织组成。其每一束针状铁素体由许多位相相同,厚度大约200纳米的薄铁素体片组成。其奥氏体有两种形态:一种是存在于针状铁素体之间的近似于等轴形的块状奥氏体;一种是存在于针状铁素体之内的薄片形奥氏体。从晶粒尺寸数量级来说,针状铁素体的厚度约为200纳米,而铁素体内奥氏体的厚度仅为几到10纳米数量级。金属强化的几种主要方式:细晶强化,位错强化,晶界与亚结构强化,第二相强化,固溶强化,细晶强化以及TRIP强化等都在等温淬火球铁中得到了体现。正是由于等温淬火球铁这种特有的微观组织使其具有了优越的力学性能。

The microstructure of isothermally-quenched ductile iron （ADI） is a mixture structure consisting of austenite plus acicular ferrite. Every its bunch ferrite consists of many phase-equal ferrite thin slices with thickness of about 200nm. Its austenite has two types of morphologies： one type is the austenite which is existing between the acicular ferrite and has approximately equiaxial block shape; another type is the austenite which is existing inside the＇acicular ferrite and has thin slice shape. So far as the grain size order of magnitude is concerned, the thickness of the acicular ferrite is about 200nm, while the thickness of the austenite existing inside the ferrite is only several nm to 10 nm. All main ways of metal strengthening including grain refining strengthening, dislocation strengthening, grain boundary and substructure strengthening, second phase strengthening, solid solution strengthening, as well as TRIP strengthening and so on, have totally found expression in the ADI. And just such peculiar microstructure is the very contributing factor that causes ADI to have excellent properties.