1 Introduction
2 Experimental Methods
2.1 Material, Heat Treatments, and Hardness Measurements
C | Si | Mn | Cr | Ni | Nb | S | P | Al | Cu | Fe |
---|---|---|---|---|---|---|---|---|---|---|
0.61 | 0.21 | 0.36 | 0.10 | 0.90 | max 0.05 | 0.0007 | 0.0090 | 0.0040 | 0.01 | bal. |
2.2 Microscopy
2.3 XRD
2.4 Thermodynamic Calculations and Kinetic Simulations
3 Results and Discussion
3.1 Grain Boundary Strengthening
Sample | Number of Grains Measured | Total Number of Images | Measured Thickness [nm] | t [nm], from Eq. [1] |
---|---|---|---|---|
10 min | 321 | 48 | 104±33 | 66 |
24 h | 355 | 40 | 101±24 | 64 |
3.2 Softening Due to Retained Austenite
3.3 Precipitation Strengthening
Sample | Number | Length (nm) | Width (nm) | d (nm) |
---|---|---|---|---|
10 min | 298 | 91±46 | 39±13 | 65 |
24 h | 277 | 85±34 | 40±16 | 63 |
3.4 Solid Solution Strengthening
3.4.1 Substitutional alloying elements
3.4.2 Interstitial alloying elements
Average Carbon Content | Atom Probe Tomography | X-ray Analysis | ||||
---|---|---|---|---|---|---|
Ferrite | Ferrite | Austenite | ||||
At Pct | Wt Pct | At Pct | Wt Pct | At Pct | Wt Pct | |
10 min | 0.53 ± 0.31 | 0.12 ± 0.07 | 0.29 ± 0.23 | 0.065 ± 0.05 | 11.3 ± 0.57 | 2.66 ± 0.18 |
24 h | 0.48 ± 0.13 0.20 ± 0.13 | 0.11 ± 0.03 0.04 ± 0.03 | 0.08 ± 0.14 | 0.017 ± 0.03 | 10.6 ± 0.19 | 2.49 ± 0.05 |
3.5 Effect of Dislocations and Internal Stresses on Hardness
Temperature (°C) | Dislocation Density (m−2) | Material | Author |
---|---|---|---|
300 | 6.30 × 1015 | EN 24 medium carbon | Fondekar[41] |
360 | 4.66 × 1015 | EN 24 medium carbon | Fondekar[41] |
400 | 4.06 × 1015 | EN 24 medium carbon | Fondekar[41] |
200 | 6.72 × 1015 | 0.80C, 1.59Si, 2.01Mn, 1Cr1.51Co | Garcia-Mateo[10] |
250 | 4.84 × 1015 | 0.80C, 1.59Si, 2.01Mn, 1Cr1.51Co | Garcia-Mateo[10] |
300 | 3.22 × 1015 | 0.80C, 1.59Si, 2.01Mn, 1Cr1.51Co | Garcia-Mateo[10] |
200 | 5.89 × 1015 | 0.79C, 1.56Si, 1.98Mn, 1.01Cr1.51Co, 1.01Al | Garcia-Mateo[10] |
250 | 4.84 × 1015 | 0.79C, 1.56Si, 1.98Mn, 1.01Cr1.51Co, 1.01Al | Garcia-Mateo[10] |
300 | 2.28 × 1015 | 0.79C, 1.56Si, 1.98Mn, 1.01Cr1.51Co, 1.01Al | Garcia-Mateo[10] |
10 min 300 | 1.35 × 1016 | 0.61C, 0.21Si, 0.36Mn, 0.9Ni, 0.10Cr | this work |
2 h 300 | 7.75 × 1015 | 0.61C, 0.21Si, 0.36Mn, 0.9Ni, 0.10Cr | this work |
10 h 300 | 6.23 × 1015 | 0.61C, 0.21Si, 0.36Mn, 0.9Ni, 0.10Cr | this work |
24 h 300 | 5.23 × 1015 | 0.61C, 0.21Si, 0.36Mn, 0.9Ni, 0.10Cr | this work |
300 | 7.41 × 1015 | theoretical estimation | Peet[6] |
500 | 1.2 × 1014 | 0.25C, 2.07Mn, 0.021Al | He[42] |
400 | 6.5 × 1014 | 0.25C,2.07Mn, 0.021Al | He[42] |
400 | 1.0 × 1015 | 0.25C, 2.07Mn, 0.053Al | He[42] |