Optimising the strength-ductility-toughness combination in ultra-high strength quenching and partitioning steels by tailoring martensite matrix and retained austenite
Optimising the strength-ductility-toughness combination in ultra-high strength quenching and partitioning steels by tailoring martensite matrix and retained austenite
复制标题
通过调整马氏体基体和残余奥氏体来优化超高强度淬火和分配钢的强度-塑性-韧性组合
DOI：
10.1016/j.ijplas.2020.102851
复制
发表时间：
2020-11
影响因子：
9.8
通讯作者：
M.X. Huang
中科院分区：
文献类型：
--
作者：
Z. Wang;M.X. Huang
不期望的抗断裂性已经导致超高强度淬火和分配（Q&P）钢中的关键安全问题。本文提出了一种新的热处理方法，即同时剪裁马氏体基体和残余奥氏体，以提高超高强度Q&P钢的断裂抗力，同时保持良好的强度-塑性组合。为此，对具有由不同马氏体基体和残余奥氏体组成的各种显微组织的不同Q&P钢进行常规拉伸试验和预裂拉伸试验。用中子衍射、原子探针层析成像、透射电子显微镜和透射电子显微镜分析了显微结构。对于最佳组织，残余奥氏体的体积分数对提高强度-塑性配合起重要作用，其极限抗拉强度达到1500 MPa，均匀延伸率超过10%。此外，由于位错回复、溶质碳贫化和过渡碳化物向马氏体的转变，最佳组织的马氏体基体中的位错活动性增强。位错活动性的增强降低了流动应力，并导致马氏体基体的本征韧性的改善。此外，在最佳显微组织的晶界处的磷灰石的尺寸是如此之小（几十纳米），从而防止了脆性沿晶断裂。总之，新的热处理方法表明，最佳处理应同时调整马氏体基体和残余奥氏体，以优化超高强度Q&P钢的强度、延展性和抗断裂性组合。
Undesirable fracture resistance has led to critical safety concerns in ultra-high strength quenching and partitioning (Q&P) steels. The present work proposes a new heat treatment method of tailoring simultaneously martensite matrix and retained austenite to enhance the fracture resistance of ultra-high strength Q&P steels, while keeping the good strength-ductility combination. To this end, both conventional and pre-cracked tensile tests are conducted on different Q&P steels with various microstructures consisting of different martensite matrix and retained austenite. Microstructure is analysed by neutron diffraction, atom probe tomography, transmission electron microscopy and dilatometry. For the optimum microstructure, the volume fraction of retained austenite play an important role in enhancing the strength-ductility combination, with an ultimate tensile strength reaching 1500 MPa and uniform elongation over 10%. In addition, the dislocation mobility in the martensite matrix of the optimum microstructure is enhanced due to the dislocation recovery, solute carbon depletion, and the transformation of transition carbides into cementite. The enhanced dislocation mobility reduces the flow stress and results in an improvement of intrinsic toughness of the martensite matrix. Furthermore, the size of cementite at grain boundaries of the optimum microstructure is so small (tens of nanometres) that brittle intergranular fracture is prevented. In summary, the new heat treatment method suggests that the optimal treatment should tailor simultaneously the martensite matrix and the retained austenite to optimise the strength, ductility and fracture resistance combination of ultra-high strength Q&P steels.
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