等温淬火球铁(ADI)的微观组织与力学性能

Microstructure and Mechanical Properties of Austempered Ductile Iron(ADI)

ADI的显微组织由奥氏体加上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 nm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内的薄条形奥氏体。从晶粒尺寸数量级来说,针状铁素体的厚度约为200 nm,而铁素体内奥氏体的厚度仅为几到10 nm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、固溶强化等都在ADI得到了体现。正是由于ADI这种特有的微观组织使其具有了优越的力学性能。

The microstructure of ADI is a mixture of austenite and acicular ferrite. Each ＂sheaf＂ of acicular ferrite platelets consists of fine ferrite plates with thickness of about 200 nm, There are two types of austenite in ADI： （1） block austenite with equiaxed shape between non-parallel acicular structures, and （2） the thin films of austenite between the individual ferrite platelets in the acicular structure. From the scale of grain size, the thickness of the fine ferrite plates is about 200 nm, whereas the thickness of austenite inside ferrite platelets is only from several nm to 10 nm. All the strengthening mechanisms such as fine grain strengthening, grain boundary strengthening, dislocation strengthening, solid solution strengthening, second phase strengthening and phase transformation strengthening play their roles in enhancing the properties of ADI. It is the unique microstructure that makes ADI have excellent properties.