The mechanism of twin thickening and the elastic strain state of TWIP steel nanotwins
The mechanism of twin thickening and the elastic strain state of TWIP steel nanotwins
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DOI：
10.1016/j.msea.2023.145005
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发表时间：
2022-09
期刊：
影响因子：
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通讯作者：
Twj Kwok;TP McAuliffe;AK Ackerman;B. Savitzky;M. Danaie;C. Ophus;D. Dye
中科院分区：
文献类型：
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作者：
Twj Kwok;TP McAuliffe;AK Ackerman;B. Savitzky;M. Danaie;C. Ophus;D. Dye
将名义成分为Fe-16.4Mn-0.9C-0.5Si-0.05Nb-0.05V的孪生诱发塑性(TWIP)钢变形为6%的工程应变。使用4D-STEM技术绘制了形变孪晶周围的应变图。应变图显示，在平行和垂直于孪晶方向的方向上有大约6%的大的平均弹性应变。然而，大的平均菌株由几个热点组成，甚至更大的菌株高达12%。这些热点可以归因于孪晶界上高密度的固位型Frank位错，并对应于1-1.5 Gpa的剪应力。应变和应力场比其他已知的孪晶材料要大得多，并被认为是导致TWIP钢纳米孪晶早期厚度饱和的原因。保持孪晶极薄的能力有助于改善晶粒破碎，即动态霍尔-佩奇效应，并支持TWIP钢的高延伸率和应变硬化率。
A Twinning Induced Plasticity (TWIP) steel with a nominal composition of Fe-16.4Mn-0.9C-0.5Si-0.05Nb-0.05V was deformed to an engineering strain of 6%. The strain around the deformation twins were mapped using the 4D-STEM technique. Strain mapping showed a large average elastic strain of approximately 6% in the directions parallel and perpendicular to the twinning direction. However, the large average strain comprised of several hot spots of even larger strains of up to 12%. These hot spots could be attributed to a high density of sessile Frank dislocations on the twin boundary and correspond to shear stresses of 1–1.5 GPa. The strain and therefore stress fields are significantly larger than other materials known to twin and are speculated to be responsible for the early thickness saturation of TWIP steel nanotwins. The ability to keep twins extremely thin helps improve grain fragmentation,i.e.the dynamic Hall–Petch effect, and underpins the large elongations and strain hardening rates in TWIP steels.