锻态奥氏体基低密度钢的低温高速冲击力学行为

Mechanical behavior of an as-forged austenite-based low-density steel under high-speed impact loading at cryogenic temperature

为了评价锻态奥氏体基低密度钢在低温环境下抵抗高速冲击能力的大小,采用分离式霍普金森压杆(SHPB)试验装置对尺寸为φ3.94 mm×2.88 mm的锻态奥氏体基低密度钢Fe-28.13Mn-10.04Al-1.05C(Mn28Al10)试样在-50℃下进行了工程应变速率约为4 300s^(-1)的低温高速冲击压缩试验,研究了该钢在上述试验条件下的低温高速冲击力学行为。试验结果表明,被冲试样在低温高速冲击过程中先后经历了约18μs的压缩弹性变形、约110μs的压缩塑性变形、约20μs的拉伸塑性变形和断裂。被冲试样断裂前所吸收的塑性功约为1 558J/cm^(3),绝热温升约为178℃。被冲试样的应力-应变曲线呈现出典型的应变强化特征,绝热温升的存在使得应力-应变曲线出现了波浪形起伏现象。低温高速冲击试样被冲断成以压缩塑性变形所致断裂和拉伸塑性变形所致断裂的3个断块,断口呈现出明显的压缩区和拉伸区,均属于以韧窝为特征的韧性断裂。压缩区和拉伸区附近的亚结构均为高密度可动位错,压缩变形区的位错密度比拉伸变形区低,而压缩变形区的高密度位错区的长度和宽度比拉伸变形区大。锻态Mn28Al10低密度钢在-50℃和工程应变率约4 300s-1下的变形机制是位错滑移。

In order to evaluate the ability of the as-forged austenite-based low-density steel to resist high-speed impact loading at low temperature,a low-temperature and high-speed impact test using a Split Hopkinson Pressure Bar(SHPB)apparatus at -50℃and engineering strain rate of about 4 300 s^(-1) was carried out on an as-forged austenite-based low-density steel sample of Fe-28.13Mn-10.04Al-1.05C(Mn28Al10)with dimensions of φ3.94 mm×2.88 mm.The mechanical behavior of the steel at low-temperature and high-speed impact loading was studied.The result showed that,the impacted sample experienced elastic deformation of about 18μs,compression plastic deformation of about 110μs,tensile plastic deformation of about 20μs and fracture under the above-mentioned experimental process.The plastic energy and the adiabatic temperature rise of the impacted sample before fracture were about 1 558 J/cm3 and 178 ℃,respectively.The stress-strain curve of the impacted sample showing a typical strainstrengthening characteristic,and the existence of adiabatic temperature rise made the stress-strain curve showed fluctuation phenomenon.The impacted sample was broken down into three fragments,which were induced mainly by compression plastic deformation and tensile plastic deformation.The fracture showed compression zone and tensile zone,both of which belong to ductile fracture characterized by the dimple.The substructures of the deformation zone near the compression zone and the tensile zone were all high-density movable dislocations.The dislocation density of the compression deformation zone is lower than that of the tension deformation zone,and the length and width of the high-density dislocation in the compression deformation zone were larger than that in the tension deformation zone.The deformation mechanism of the as-forged austenite-based low-density steel of Mn28Al10 at -50℃and engineering strain rate of about 4 300 s-1 was dislocation slip.