不锈钢0Cr18Ni10Ti焊接头高温、高应变率下的动态力学性能

DYNAMIC MECHANICAL PROPERTIES OF STAINLESS STEEL 0Cr18Ni10Ti WELDED JOINT AT ELEVATED TEMPERATURES AND HIGH STRAIN RATES

利用带有加热装置和同步组装系统的Hopkinson压杆系统对反应堆工程管道材料0Cr18Ni10Ti焊接头的母材和焊缝进行了高温、高应变率下的动态力学性能测试.实验的应变率范围为200—3800 s^(-1),温度范围为25—600℃,得到了材料在不同温度和应变率耦合作用下的应力-应变曲线。着重考察了两种材料塑性流变应力的温度和应变率敏感性,并得到了它们的Johson-Cook(J-C)模型.实验表明,母材和焊缝材料均具有较强的热软化效应及应变强化效应,而应变率强化效应相对较弱,并且这些效应本身也受到温度的影响.温度较高时,材料的塑性流变应力受应变和应变率强化的程度减弱,在一定变形量下甚至出现降低趋势.根据热激活位错运动理论对上述现象的内在机理进行了解释和探讨,并对试样的金相组织进行了观察和分析.

Dynamic mechanical behaviors of base and weld materials for the reactor engineering pipeline material, 0Cr18Ni10Ti, are studied at elevated temperatures and high strain rates with split Hopkinson pressure bar （SHPB）, which is installed with heating and synchro assembly system. The tests are carried out at loading rates ranging from 200 to 3800 s^-1 and temperatures ranging from 25 to 600 ℃, and different stress-strain curves are obtained correspondingly for each condition. Emphasis is put on the study of strain rate and temperature sensitivity of plastic flow stress, and the Johson- Cook （J-C） models are obtained for both the materials. The results show that the base and the weld materials both have evident heat softening effect and strain hardening effect, but the effect of strain rate hardening is comparatively weaker. Meanwhile, these effects are also effected by temperature, and the hardening effects induced by strain and strain rate are weakened at higher temperature. With the increase of strain, the flow stress of both the materials even begin to decrease at a certain deformation. The intrinsic mechanism is discussed according to the thermally activated dislocation motion theory. Optical microstructures of the materials are also observed and analyzed.