Mechanical properties of iron processed by severe plastic deformation
Mechanical properties of iron processed by severe plastic deformation
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DOI：
10.1007/s11661-003-0209-7
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
B. Han;F. Mohamed;E. Lavernia
中科院分区：
文献类型：
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作者：
B. Han;F. Mohamed;E. Lavernia
本文首次研究了室温条件下等通道转角挤压（ECAP）对Fe合金力学性能的影响。退火Fe的晶粒尺寸（初始晶粒尺寸约为200µm）在ECAP过程中急剧减小。经过8次后，晶粒尺寸达到200至400 nm，如通过透射电子显微镜（TEM）所记录的。在压制过程中的显微硬度的值增加3倍以上的起始材料后，第一道次，并在随后的压制过程中稍有增加，为更高纯度的Fe。检查八次通过后的显微硬度值与ECAP后退火温度的函数关系，显示从恢复到再结晶的转变，这一观察结果类似于严重变形金属和合金所报告的行为。研究了复合材料的拉伸和压缩性能。在拉伸，超过最大载荷的工程应力-工程应变曲线中的下降被观察到在退火Fe和ECAP Fe。这种下降与颈部变形有关。用扫描电子显微镜（SEM）观察断裂表面，发现断裂表面有脉纹，这与退火态Fe断裂表面上的韧窝不同。在压缩过程中，观察到的ECAP铁的初始应变硬化区，随后的非应变硬化区。拉伸屈服强度高于压缩屈服强度。讨论了其强化机理和软化行为。
In the present study, the mechanical properties of Fe processedviasevere plastic deformation (equal-channel angular pressing (ECAP)) at room temperature were investigated for the first time. The grain size of annealed Fe, with an initial grain size of about 200µm, was reduced drastically during ECAP. After eight passes, the grain size reaches 200 to 400 nm, as documented by means of transmission electron microscopy (TEM). The value of microhardness during pressing increases 3 times over that of the starting material after the first pass and increases slightly during subsequent pressing for higher-purity Fe. Examination of the value of microhardness after eight passes as a function of post-ECAP annealing temperature shows a transition from recovery to recrystallization, an observation that resembles the behavior reported for heavily deformed metals and alloys. The tensile and compression behaviors were examined. In tension, a drop in the engineering stress-engineering strain curve beyond maximum load was observed both in the annealed Fe and the ECAP Fe. This drop is related to the neck deformation. The fracture surface, examined by scanning electron microscopy (SEM), shows vein patterns, which is different from the dimples found on the fracture surface of annealed Fe. In compression, an initial strain-hardening region followed by a no-strain-hardening region was observed in the ECAP Fe. The yield strength in tension of the ECAP Fe was observed to be higher than that in compression. The strengthening mechanisms and softening behavior are discussed.