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研究了无镍高氮奥氏体不锈钢的脆韧转变(BDT)。在176 K、273 K和336 K进行的落锤试验结果表明,尽管Fe-25Cr-1.1N(质量分数,%)是面心立方结构的奥氏体合金钢,但仍展现出显著的脆韧转变现象。对冲击试验试样的塑性变形观察表明,BDT是由于低温下差的延展性所致,这与铁素体钢的情况是一致的。为了测量BDT的激活能,利用4点弯曲试验研究了应变速率与BDT温度的关系。研究发现,BDT温度与应变速率之间的依赖关系不显著,且BDT温度对应变率的Arrhenius曲线表明Fe-25Cr-1.1N钢BDT的激活能比低碳铁素体钢的高得多。从滑移位错与溶质氮原子发生交互作用导致低温下位错可动性降低这一角度,本文探讨了高氮钢特有的BDT及其高激活能的本质原因。
Brittle-ductile transition (BDT) of nickel-free high-nitrogen austenitic stainless steel was investigated. The drop weight test at 176 K, 273 K and 336 K showed that although Fe-25Cr-1.1N (mass fraction,%) was a face-centered cubic austenitic alloy steel, it still showed significant brittleness and toughness Change the phenomenon. The plastic deformation observation of the impact test specimen shows that BDT is due to poor ductility at low temperatures, which is consistent with the case of ferritic steels. In order to measure the activation energy of BDT, the relationship between strain rate and BDT temperature was investigated using a 4-point bending test. The dependence of BDT temperature on strain rate is not significant, and the Arrhenius curve of BDT temperature versus strain rate shows that BDT activation energy of Fe-25Cr-1.1N steel is much higher than that of low-carbon ferritic steel. From the perspective of the interaction between slip dislocations and solute nitrogen atoms leading to the decrease of dislocation mobility at low temperature, this paper explores the intrinsic BDT of high nitrogen steel and the nature of its high activation energy.