Microstructure control of ferrous martensite by defects inherited from austenite

（1）基体位错的遗传和马氏体的析出在Fe-20%Ni-5.5%Mn的奥氏体板条马氏体中，引入奥氏体中的位错以Bain对应方式遗传到马氏体中。Fe-31%Ni-10 Co-3 Ti奥氏体中析出的Ni 3Al相继承为薄板马氏体。当由于短时效而具有更细尺寸的“α”通过相变剪切改变其结构时，在冷却中形成热弹性马氏体。当γ'尺寸随时效时间的延长而增大时，γ'的组织没有发生变化，在冷却过程中形成非热马氏体。（2）沉淀细化板条马氏体Fe-（1.5，2）Mn-0.2C合金中板条马氏体团/块的细化是通过减小奥氏体晶粒尺寸实现的。在晶粒尺寸约为2μm的奥氏体中，合金碳化物钉扎后，获得了1μm的块状晶粒。淬火后马氏体的强度随着块体尺寸的增加而呈Hall-Petch型关系。细分散的V（C，N）颗粒能够细化板条马氏体组织。（3）马氏体/贝氏体亚结构随继承位错的变化在透镜状马氏体中，亚结构由孪晶转变为位错。在马氏体/奥氏体界面附近，由于相变应变的塑性调节，奥氏体包含缠结位错。在马氏体中也观察到类似的缠结位错，导致界面附近的局部晶格取向。可以得出结论，这些位错是从周围的奥氏体中继承的。结果表明，在Fe-Ni合金中，奥氏体变形细化了板条马氏体组织，但导致上贝氏体组织粗化。

(1)Inheritance of matrix dislocation and precipitate into martensiteIn ausformed lath martensite in Fe-20%Ni-5.5%Mn, dislocations introduced in the austenite are inherited into martensite with the Bain correspondence. γ'-Ni3Al precipitated in the austenite of Fe-31%Ni-10Co-3Ti is inherited into thin-plate martensite. When γ', which has a finer size due to a short aging, changes its structure by transformation shear, thermally elastic martensite is formed in the cooling. When the γ' size gets larger by prolonged aging, no structure change occurs for γ' and athermal martensite is formed in the cooling.(2)Refinement of lath martensite by precipitationLath martensite packets/blocks are refined by decreasing austenite grain size in Fe-(1.5,2)Mn-0.2C alloys. In the austenite of which grain size is about 2μm with pinning by alloy carbide, a block size of 1μm was obtained. The strength of the as-quenched martensite increases by following a Hall-Petch type relation against the block size. Finely dispersed V(C,N) particles are capable of refining the lath martensite structure.(3)The change of martensite/bainite substructure with inherited dislocationsIn lenticular martensite, substructure changes from twinning to dislocations. Near the martensite/austenite interface, the austenite contains tangled dislocations due to plastic accommodation of transformation strain. Similar tangled dislocations are also observed in the martensite, resulting in local lattice orientation near the interface. It is concluded that those dislocations are inherited from the surrounding austenite. It is observed that the deformation of austenite prior to transformation (ausforming) refines lath martensite structures but results in the coarsening of upper bainite structures in Fe-Ni alloys.