Abstract
The size effect of α' martensite constituents before annealing on the microstructure and tensile properties of intercritically annealed medium Mn steel was systematically investigated. The cold-rolled Fe-9Mn-0.05C (wt%) steel was austenized at three different temperatures, water-quenched to room temperature to vary the sizes of the martensite constituents, and then annealed at 640°C for 10min. When the austenizing temperature increased, the sizes of the prior austenite (γ) grains and of the packets and blocks of α' martensite increased; however, the width of the laths changed only insignificantly. The annealed specimens had a dual-phase microstructure with lath-shaped ferrite (α) and retained γ (γR) phases. The volume fraction of γR decreased with increasing austenizing temperature because the specimen austenized at the higher temperature underwent a slower reverse transformation in the early stage of intercritical annealing. The slowed kinetics of the reverse transformation with increasing austenizing temperature was attributed to the reduction in area of block boundaries which provide nucleation sites for the reverted γ. The widths of the α and γR laths were almost independent of the austenizing temperature. The partitioning of Mn and C atoms from α into γR laths became active with increasing austenizing temperature, resulting in a more stable γR. The specimen austenized at higher temperature exhibited a lower strain hardening rate (SHR) due to the less active transformation-induced plasticity (TRIP) in γR with the higher phase stability. The ultimate tensile strength decreased with increasing austenizing temperature because the SHR was lowered by the less active TRIP with increasing austenizing temperature. The uniform elongation increased with increasing austenizing temperature due to delayed necking caused primarily by the flow stress, which dropped with increasing austenizing temperature.
| Original language | English |
|---|---|
| Pages (from-to) | 9-16 |
| Number of pages | 8 |
| Journal | Materials Science and Engineering A |
| Volume | 633 |
| DOIs | |
| Publication status | Published - 2015 May 1 |
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All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
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The size effect of initial martensite constituents on the microstructure and tensile properties of intercritically annealed Fe-9Mn-0.05C steel. / Han, Jeongho; Lee, Seung Joon; Lee, Chan Young; Lee, Sukjin; Jo, Seo Yeon; Lee, Young-Kook.
In: Materials Science and Engineering A, Vol. 633, 01.05.2015, p. 9-16.Research output: Contribution to journal › Article
TY - JOUR
T1 - The size effect of initial martensite constituents on the microstructure and tensile properties of intercritically annealed Fe-9Mn-0.05C steel
AU - Han, Jeongho
AU - Lee, Seung Joon
AU - Lee, Chan Young
AU - Lee, Sukjin
AU - Jo, Seo Yeon
AU - Lee, Young-Kook
PY - 2015/5/1
Y1 - 2015/5/1
N2 - The size effect of α' martensite constituents before annealing on the microstructure and tensile properties of intercritically annealed medium Mn steel was systematically investigated. The cold-rolled Fe-9Mn-0.05C (wt%) steel was austenized at three different temperatures, water-quenched to room temperature to vary the sizes of the martensite constituents, and then annealed at 640°C for 10min. When the austenizing temperature increased, the sizes of the prior austenite (γ) grains and of the packets and blocks of α' martensite increased; however, the width of the laths changed only insignificantly. The annealed specimens had a dual-phase microstructure with lath-shaped ferrite (α) and retained γ (γR) phases. The volume fraction of γR decreased with increasing austenizing temperature because the specimen austenized at the higher temperature underwent a slower reverse transformation in the early stage of intercritical annealing. The slowed kinetics of the reverse transformation with increasing austenizing temperature was attributed to the reduction in area of block boundaries which provide nucleation sites for the reverted γ. The widths of the α and γR laths were almost independent of the austenizing temperature. The partitioning of Mn and C atoms from α into γR laths became active with increasing austenizing temperature, resulting in a more stable γR. The specimen austenized at higher temperature exhibited a lower strain hardening rate (SHR) due to the less active transformation-induced plasticity (TRIP) in γR with the higher phase stability. The ultimate tensile strength decreased with increasing austenizing temperature because the SHR was lowered by the less active TRIP with increasing austenizing temperature. The uniform elongation increased with increasing austenizing temperature due to delayed necking caused primarily by the flow stress, which dropped with increasing austenizing temperature.
AB - The size effect of α' martensite constituents before annealing on the microstructure and tensile properties of intercritically annealed medium Mn steel was systematically investigated. The cold-rolled Fe-9Mn-0.05C (wt%) steel was austenized at three different temperatures, water-quenched to room temperature to vary the sizes of the martensite constituents, and then annealed at 640°C for 10min. When the austenizing temperature increased, the sizes of the prior austenite (γ) grains and of the packets and blocks of α' martensite increased; however, the width of the laths changed only insignificantly. The annealed specimens had a dual-phase microstructure with lath-shaped ferrite (α) and retained γ (γR) phases. The volume fraction of γR decreased with increasing austenizing temperature because the specimen austenized at the higher temperature underwent a slower reverse transformation in the early stage of intercritical annealing. The slowed kinetics of the reverse transformation with increasing austenizing temperature was attributed to the reduction in area of block boundaries which provide nucleation sites for the reverted γ. The widths of the α and γR laths were almost independent of the austenizing temperature. The partitioning of Mn and C atoms from α into γR laths became active with increasing austenizing temperature, resulting in a more stable γR. The specimen austenized at higher temperature exhibited a lower strain hardening rate (SHR) due to the less active transformation-induced plasticity (TRIP) in γR with the higher phase stability. The ultimate tensile strength decreased with increasing austenizing temperature because the SHR was lowered by the less active TRIP with increasing austenizing temperature. The uniform elongation increased with increasing austenizing temperature due to delayed necking caused primarily by the flow stress, which dropped with increasing austenizing temperature.
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U2 - 10.1016/j.msea.2015.02.075
DO - 10.1016/j.msea.2015.02.075
M3 - Article
VL - 633
SP - 9
EP - 16
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
SN - 0921-5093
ER -