Abstract
The strengthening mechanism of microalloyed vanadium (V) on eutectoid pearlite steel was investigated from the perspectives of nano-precipitation and lattice strain. The 0.2% proof stress of specimens, isothermally transformed at 873 K, increased by about 160–170 MPa with the addition of 0.1% V. However, the interphase precipitation of vanadium carbide (VC), regarded as the principal strengthening factor, was detected neither by transmission electron microscopy nor by 3D atom probe microscopy (3D-AP). A lattice strain in lamellar ferrite, analyzed by broadening of the X-ray diffraction peak, has been experimentally estimated to understand the strengthening mechanisms by V-addition. The lattice strain data of 0.1% V-added pearlite specimens were plotted on the same correlation line as those of the V-free specimens with proof stress. In addition, the elemental map obtained by 3D-AP showed that V atoms concentrate in lamellar cementite rather than ferrite, which could change the cementite lattice parameters and gain ferrite/cementite misfit, causing lattice strain increment. These results revealed that microalloyed V influences not only VC precipitation in lamellar ferrite but also the lattice strain increment in pearlite lamellar. In the case of pearlite steels containing at most 0.1% V, lattice strain was considered the major factor of their yield behaviors. Furthermore, 0.1% V addition did not enhance work-hardening behavior as notably as that estimated by Ashby’s work-hardening theory of dispersion-hardened crystals. Therefore, VC precipitation is not necessary for the V strengthening effect on pearlite steel.
Original language | English |
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Pages (from-to) | 1810-1818 |
Number of pages | 9 |
Journal | Isij International |
Volume | 60 |
Issue number | 8 |
DOIs | |
Publication status | Published - 2020 Aug 15 |
Externally published | Yes |
Keywords
- Microalloyed steel
- Pearlite
- Precipitation strengthening
- Vanadium
ASJC Scopus subject areas
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry