Effect of High-pressure Quenching on Pure-iron Martensite Transformation and Its Strengthening Mechanism

Industrial pure iron samples were austenitized and quenched (6°C/s cooling to room temperature) under hydrostatic pressure of 3–5 GPa. The morphology, phase transformation strengthening mechanism high-pressure martensite are analyzed by the method SEM, XRD, EBSD, TEM. Lath with hierarchical packet-block-lath structure is induced in industrial high pressure, which keeps Kurdjumov-Sachs (K-S) orientation relationship face-center-cubic (FCC) phase. Pressure refines size prior austenite depressing mobility grain boundaries, leading decrease type variants. increment dislocation density increases gradually (2.04×1013 3.14×1014 m−2) blocks refined from 3.3 0.9 µm. In addition, an enormous number twin boundaries high-density dislocations observed 5 GPa-samples, fairly rare lath low carbon steels. Superior tensile performances obtained iron, especially GPa-sample ultra-high yield strength 700 MPa excellent ductility 27%. quantitatively Olson’s model, results show that both Hall-Petch enhances increase pressure. Based on above findings, can be effectively controlled extends knowledge into martensitic offers a new avenue for developing performance metal materials.