The production of ultrafine ferrite during hot torsion testing of a 0.11 wt pct C steel
The production of ultrafine ferrite during hot torsion testing of a 0.11 wt pct C steel
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DOI：
10.1007/s11661-002-0283-2
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发表时间：
2002-09
期刊：
影响因子：
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通讯作者：
P. Hurley;B. C. Muddle;P. Hodgson
中科院分区：
文献类型：
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作者：
P. Hurley;B. C. Muddle;P. Hodgson
0.11C-1.6Mn-0.2Si钢经1250°C空冷后，在675°C等温扭转试验中获得了超细铁素体晶粒度。铁素体的晶内形成超过了约0.7~0.8的von Mise等效拉应变，且晶内铁素体的数量随应变水平的增加而继续增加。铁素体形核形成平行且紧密间隔的线性阵列或由许多离散的超细铁素体颗粒组成的“筏”。结果表明，在奥氏体内平行于宏观剪切方向发展的缺陷的变形过程中，铁素体形核(即动态应变诱发相变)。用一种模型奥氏体型Ni-30Fe合金研究了奥氏体亚结构在类似于诱发晶内铁素体的试验条件下的发展。结果表明，在测试过程中形成的最普遍的特征是微带。结果表明，在较低应变下，相交微带周围的高能弯曲区为铁素体的形核提供了潜在的形核位置，而在较高应变下，微带的壁也可能起到形核的作用。
Ultrafine ferrite grain sizes were produced in a 0.11C-1.6Mn-0.2Si steel by torsion testing isothermally at 675 °C after air cooling from 1250 °C. The ferrite was observed to form intragranularly beyond a von Mises equivalent tensile strain of approximately 0.7 to 0.8 and the number fraction of intragranular ferrite grains continued to increase as the strain level increased. Ferrite nucleated to form parallel and closely spaced linear arrays or “rafts” of many discrete ultrafine ferrite grains. It is shown that ferrite nucleates during deformation on defects developed within the austenite parallel to the macroscopic shear direction (i.e., dynamic strain-induced transformation). A model austenitic Ni-30Fe alloy was used to study the substructure developed in the austenite under similar test conditions as that used to induce intragranular ferrite in the steel. It is shown that the most prevalent features developed during testing are microbands. It is proposed that high-energy jogged regions surrounding intersecting microbands provide potential sites for ferrite nucleation at lower strains, while at higher strains, the walls of the microbands may also act as nucleation sites.