Liu Jiabin, Jin Yongbin, Fang Xiaoyang, Chen Chenxu, Feng Qiong, Liu Xiaowei, Chen Yuzeng, Suo Tao, Zhao Feng, Huang Tianlin, Wang Hongtao, Wang Xi, Fang Youtong, Wei Yujie, Meng Liang, Lu Jian, Yang Wei
State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an 710049, China.
College of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
Sci Rep. 2016 Oct 14;6:35345. doi: 10.1038/srep35345.
Strength and ductility are mutually exclusive if they are manifested as consequence of the coupling between strengthening and toughening mechanisms. One notable example is dislocation strengthening in metals, which invariably leads to reduced ductility. However, this trend is averted in metastable austenitic steels. A one-step thermal mechanical treatment (TMT), i.e. hot rolling, can effectively enhance the yielding strength of the metastable austenitic steel from 322 ± 18 MPa to 675 ± 15 MPa, while retaining both the formability and hardenability. It is noted that no boundaries are introduced in the optimized TMT process and all strengthening effect originates from dislocations with inherited thermal stability. The success of this method relies on the decoupled strengthening and toughening mechanisms in metastable austenitic steels, in which yield strength is controlled by initial dislocation density while ductility is retained by the capability to nucleate new dislocations to carry plastic deformation. Especially, the simplicity in processing enables scaling and industrial applications to meet the challenging requirements of emissions reduction. On the other hand, the complexity in the underlying mechanism of dislocation strengthening in this case may shed light on a different route of material strengthening by stimulating dislocation activities, rather than impeding motion of dislocations.
如果强度和延展性是由强化和增韧机制之间的耦合所导致的，那么它们是相互排斥的。一个显著的例子是金属中的位错强化，这总是会导致延展性降低。然而，在亚稳态奥氏体钢中这种趋势得以避免。一步热机械处理（TMT），即热轧，能够有效地将亚稳态奥氏体钢的屈服强度从322±18MPa提高到675±15MPa，同时保持其成形性和淬透性。需要注意的是，在优化的TMT过程中没有引入晶界，所有的强化效果都源于具有继承热稳定性的位错。这种方法的成功依赖于亚稳态奥氏体钢中解耦的强化和增韧机制，其中屈服强度由初始位错密度控制，而延展性则通过形核新位错以承载塑性变形的能力得以保留。特别是，加工过程的简单性使得规模化和工业应用成为可能，以满足减排的挑战性要求。另一方面，这种情况下位错强化的潜在机制的复杂性可能会通过刺激位错活动而不是阻碍位错运动，为材料强化的不同途径提供启示。
