To deal with the problem of poor yield strength and hardness in the initial use of high-manganese austenitic steel, we investigated the alloying design, microstructure, precipitates, mechanical properties, and comprehensive strengthening mechanism of high-manganese austenitic steel through two novel heat-treatment processes, namely continuous heating process (CHP) and segmented heat preservation process (SHPP). In this work, austenitic Fe-0.9C-17Mn-0.8Si-2.0Cr-0.3Ni-0.5Cu-0.7Mo steels alloyed with Ti, V, and Nb were designed. The grain size of SHPP steels was smaller than that of CHP steels due to the smaller size of precipitates. The results of mechanical experiments showed that the yield strength and impact toughness of SHPP steel were obviously higher than those of CHP steel, but the Brinell hardness of CHP steel was higher than that of SHPP steel. The higher Brinell hardness and poorer impact toughness of CHP steel were mainly due to the larger-sized precipitates. Finally, solid-solution strengthening played the most effective role of increasing the yield and tensile strengths of the two steels.

In this work, tungsten carbide particles (WC_p, spherical and irregular particles)-reinforced iron matrix composites were manufactured utilizing a liquid sintering technique. The mechanical properties and the fracture mechanism of WC_p/iron matrix composites were investigated theoretically and experimentally. The crack schematic diagram and fracture simulation diagram of WC_p/iron matrix composites were summarized, indicating that the micro-crack was initiated both from the interface for spherical and irregular WC_p/iron matrix composites. However, irregular WC_p had a tendency to form spherical WC_p. The micro-cracks then expanded to a wide macro-crack at the interface, leading to a final failure of the composites. In comparison with the spherical WC_p, the irregular WC_p were prone to break due to the stress concentration resulting in being prone to generating brittle cracking. The study on the fracture mechanisms of WC_p/iron matrix composites might provide a theoretical guidance for the design and engineering application of particle reinforced composites.

Herein, the effects of height-diameter ratios (H/D) on the microstructure evolution and mechanical properties of 0.4C-Si-Mn-Cr steel during high temperature deformation are reported. The compression experiments were performed on steel samples using Gleeble to obtain a reasonable deformation temperature, and the degree of deformation was assessed in the range of 1.5 to 2.0 H/D via forging. The forged specimens were quenched using the same heat treatment process. The hardness and impact toughness of the steel samples were tested before and after heat treatment. Grain sizes gradually increased with an increase in the compression temperature from 950 °C to 1150 °C, and the grain sizes decreased with an increase in H/D. The microstructure of the steel samples contained pearlite, bainite, martensite, and retained austenite phase. The microstructure after forging was more uniform and finer as compared to that of as-cast steel samples. The hardness and impact toughness of the steel samples were evaluated after forging; hardness first increased and then decreased with an increase in H/D, while the impact toughness continuously increased with an increase in H/D. Hence, the microstructure and properties of steel could be improved via high temperature deformation, and this was primarily related to grain refinement.

In this paper, WC particles reinforced steel matrix composites (WC_P/SMC) doped with rare-earth elements Y, Ce, La, and Nd, are manufactured via powder metallurgy sintering. The interface and mechanical properties of WC_P/SMC are theoretically and experimentally investigated. The microstructures are observed through SEM, EDS and XRD. The properties are determined by compression and micro-hardness tests. The effects of rare-earth element doping on interface and mechanical properties of composites are investigated. The results indicate that composites mainly consist of α-Fe, W₂C, WC, and Fe₃W₃C. In addition, the doping can accelerate the inter-atomic diffusion of the atoms in the interfacial reaction zone, promote the formation of Fe₃W₃C phase, and widen the interfacial reaction zone. Doping of rare-earth elements can reduce the hardness difference between the interfacial reaction zone and the composite matrix from 10.15 to 5.71 GPa and increases the compressive strength from 296.7 to 659.2 MPa. First-principles calculations indicate that doping of rare earth can reduce the interfacial, formation, and dissolution energy between the WC particles and the iron matrix. Thus, the stability of the interfacial reaction zone and bonding between the WC particles and the matrix is improved. By comparing the results with first-principles based calculations, composites doped with Nd have the best relative reaction interface bonding and mechanical properties.

Alloyed high manganese steel is a general type of wear-resistant steel, and its precipitates and austenite matrix grain sizes play an important role in impact abrasive wear behavior. Solid-solution treatment is an effective method to balance the size of the austenite grains and precipitates. This work attempts to find a new progressive solid-solution treatment to make alloyed high manganese steel castings refine the microstructure and balance the wear resistance under impact abrasive wear conditions. Compared with traditional solid-solution treatment, the MC- and M₂₃C₆-type carbide precipitates resulting from progressive solid-solution treatment decrease, and the tensile strength and impact toughness of steel are significantly increased. After the solid-solution treatment at different heating rates, the grain refinement effect is remarkable after shortening the holding time at 1100 °C and increasing the heating rate to 150 °C h⁻¹. The impact abrasive wear test results show that, compared with the traditional solid-solution treatment at 1100 °C for 4 h, the wear resistance of high manganese steel has a 23.1% improvement after progressive solution treatment at 1100 °C for 2 h, and the wear failure forms of all the experimental steels are microcutting, oxidation wear and plastic deformation.