【摘要】 本文对ZG25铸钢以不同的加热温度和不同的冷却速度形成魏氏组织的规律进行了研究。结果表明,无论是细小的9号奥氏体品粒还是粗大的1号奥氏体晶粒,只要冷却速度适宜都可以产生魏氏组织。这说明魏氏组织是一种正常的组织转变产物。而不是过热的标志。也探讨了魏氏组织对钢的力学性能的影响,认为在相同奥氏体晶粒度下有魏氏组织的退火组织比无魏氏组织的具有较高的综合力学性能,主要表现在强度和冲击韧性的提高及韧脆转变温度下降。作者队为,韧性的提高是由于伴随魏氏组织的产生,有效地细化铁素体晶粒和珠光体晶团的结果;相反地,退火组织的晶粒粗大及沿铁素体晶界析出碳化物导致其脆性增加。同时初步探讨了等轴铁素体和针状铁素体的亚结构,结果表明,两者的位错组态无本质区别,只是位错密度不同而已。更多还原

【Abstract】 This paper deals with the study on the law of the formation of the Widmanstatten structure in ZG25 steel, which was tested in different heating temperatures and different cooling rates. The results denoted that, whether the austenitic grain size is small (grain size number 9)or large(grain size number 1), the Widmanstatten structure can be produced in all undercooling austenite with proper rate of cooling.This shows that the Widmanstatten structure is not the indication of overheating, but rather a kind of normal structural transformation product, and the influences of the Widmanstatten structure on mechanical properties were also analysed. The results show that as the structures with the Widmanstatten structure compared with the annealing structures without the Widmanstatten structure, the former have better mechanical properties, mainly, the strength and toughness being increased as well as the ductility to brittle transition temperature being lowered. The auther suggests that the increase of toughness is due to the ferritic grain size and the pearlitic sphere size were effectively refined with the formation of the Widmanstatten structure. Conversely, The large grain size of the annealing structures and the carbide precipitation along the ferritic grain boundary lead to the increase of the brittleness. The sub structures of the mass ferrite and the needle ferrite were studied. The result shows that two types of ferrite have no substantial difference in the dislocation state but only in the dislocation density.更多还原