Effects of prior microstructures and deformation parameters on the ultra-refining uniformity of Ti-Mo ferritic steel
Effects of prior microstructures and deformation parameters on the ultra-refining uniformity of Ti-Mo ferritic steel
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DOI：
10.1016/j.msea.2018.07.006
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发表时间：
2018-08
期刊：
影响因子：
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通讯作者：
Lei Cheng;Wei Yu;Q. Cai;J. Lv;H. Miura
中科院分区：
文献类型：
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作者：
Lei Cheng;Wei Yu;Q. Cai;J. Lv;H. Miura
将具有准多边形铁素体（QPF）基体和多边形铁素体（PF）基体两种不同微观结构的样品，以不同的应变速率在500 ℃下进行压缩。在小应变速率下，QPF基体的微观组织更倾向于压缩细化，而PF基体则相反。将变形温度分别提高到600 ℃和700 ℃，说明cDRX过程中，几何必要边界（gnb）的扩展增加了流变应力，而几何必要位错（GNDs）的重排是导致软化现象的主要原因。此外，先前晶粒中gnb的延伸首先促进了织构强度在某些取向上的增加，然后随着连续动态再结晶（cDRX）过程的进一步进行，织构强度降低，在此过程中，亚晶粒主要沿< 001 > //SD或< 111 > //SD旋转，使纤维织构内的取向分布更加随机。600 ℃变形的细化效果较好，平均晶粒尺寸可细化到亚微米级，而700 ℃变形的超细化均匀性较好，超细化区面积分数可达94.8%，平均晶粒尺寸为1.1 µm。TEM观察表明，随着变形温度的升高，低角度晶界（LABs）将取代位错壁，对原有晶粒进行划分，并表现出更好的扩展能力。cDRX反应的活化能约为768 KJ/mol。
Samples with different prior microstructures, quasi-polygonal ferritic (QPF) matrix and polygonal ferritic (PF) matrix, were compressed at 500 ℃ with different strain rates. As for the QPF matrix, its microstructure more tend to be compressed and refined under small strain rate, while it is opposite for the PF matrix. Increase of deformation temperature to 600 ℃ and 700 ℃ illustrates that during cDRX process, extending of geometric necessary boundaries (GNBs) increases the flow stress whereas the rearrangement of geometric necessary dislocations (GNDs) mainly causes the softening phenomenon. Additionally, extending of GNBs in prior grains firstly facilitates the increase of texture intensity on certain orientations, then the texture intensity decreases with further conduct of continuous dynamic recrystallization (cDRX) process, during which the subgrains mainly rotate along < 001 > //SD or < 111 > //SD and make orientations distributed more randomly within fiber textures. Deformation at 600 ℃ shows better refining effect and the average grain size can be refined to submicron scale, however, deformation at 700 ℃ presents better ultra-refining uniformity that the area fraction of ultra-refined regions can reach 94.8% with an average grain size of 1.1 µm. TEM observation clarifies that with the increase of deformation temperature, low angle boundaries (LABs) will replace dislocation walls dividing the prior grains and show better extending ability. Activation energy of the cDRX process also been estimated and it is about 768 KJ/mol.