冲击载荷下低屈服比高强钢板的拉伸性能

通过室温下的仪器化冲击试验和静态拉伸试验,研究一种低屈服比高强度钢板在冲击载荷下的力学性能和断裂机理.结果表明:试验钢的组织由细小岛状马氏体与针状铁素体为主构成,马氏体体积分数为27.6%.与静态拉伸性能相比,在名义应变速率为100 s-1的冲击载荷作用下,试验用钢屈服强度提高31.6%,延伸率不降低.在静态和动态载荷下,该钢均以显微空洞长大聚集的方式发生韧性断裂,但显微空洞的形核和长大方式不同.在静态载荷下,显微空洞形核于颈缩区的铁素体晶粒内部或铁素体-马氏体两相界面处,空洞主要通过两相界面的脱开而形成长大;在动态载荷下,显微空洞主要形核于颈缩区的两相界面处,空洞主要通过马氏体粒子的开裂而形成长大.

Tensile Properties of High Strength Steel Sheet with Low Yield Ratio under Impact Loading

Mechanical properties and fracture mechanism of high strength steel sheet with low yield ratio under impact loading have been studied through instrumented impact and quasi-static tensile tests.The results showed that the microstructure of the steel was mainly composed of fine island-like martensite and acicular ferrite,with a 27.6% of martensite volume fraction.Compared to that under quasi-static tensile loading,the yield strength of the steel increased by 31.6% with no reduction of elongation under impact loading at the nominal strain rate of 100s~(-1).The fracture mode was dimple type under both loading conditions.Microvoid mostly formed within the fer- rite grains or at the ferrite-martensite interfaces in the necking vicinity and the void grew up by the decohesion of ferrite-martensite interface under quasi-static tensile loading,while microvoid mainly developed at the ferrite-mar- tensite interfaces in the necked region and the void grew up by the fracture of martensite particles under dynamic loading.