Uncovering the mechanism of dislocation interaction with nanoscale (<4 nm) interphase precipitates in microalloyed ferritic steels

Figures & data

Figure 1. Interphase precipitation in the steel after thermo-mechanical processing: a. Bright field image and (b) associated selected area diffraction pattern with zone axis $[011{]}_{\alpha }||[010{]}_{\text{VC}}$. The additional unindexed diffraction spots originate from (Nb,V)C particles formed in austenite; c. Dark field image taken using the ${200}_{\text{VC}}$ reflection in b. d HR-STEM micrograph showing rows of interphase precipitates marked with red ovals; e. V EDS map showing two rows of VC marked with red ovals. f. A representative HAADF-STEM atomically resolved micrograph of carbide particle in bcc matrix down the $[011{]}_{\alpha }$ zone axis. Carbide particle is outlined by the dash lines.

Figure 2. DFT simulation of the a. (100)_α||(100)_VC, [011]_α||[010]_VC interface and b. (011)_α||(010)_VC, [100]_α||[100]_VC interface. c. Bright Field (BF)-STEM image with overlay $\left[011\right]$_α||[010]_VC zone axis view of the model (upper black box) and the corresponding simulated BF-STEM image from the DFT model in (b) (lower red box). The intensity profiles originate from the arrows within the images with their respective colour (bottom). Fe atoms- green, V- blue and C-red.

Figure 3. STEM-HAADF images of VC after deformation: a., b. and c. Ex-situ uniaxial tensile test and d. In-situ compression of pillars. Arrows indicate the steps at the particle/matrix interfaces. The matrix is imaged down the $[011{]}_{\alpha }$ zone axis.

Figure 4. DFT simulation results of $(100{)}_{\alpha }||{\left(100\right)}_{\text{VC}},{\left[0\overline{1}1\right]}_{\alpha }||[001{]}_{\text{VC}}$ interfaces after imposed shear ${\overrightarrow{b}}_{\alpha }:\frac{a_{\alpha }}{2}\left[\overline{1}11\right]$ on the $\alpha$ matrix and VC precipitate: a. before relaxation, b. after relaxation and c. electron density state after relaxation. The in-plane component of the shear is $\overrightarrow{b_{\alpha }^{\ast }}:\frac{a_{\alpha }}{2}$$\left[\overline{1}00\right]$ and the out-of-plane component is $\frac{a_{\alpha }}{2}\left[011\right]$. Fe atoms- green, V atoms- blue and C atoms- red.