Bin Gan’s scientific contributions

Combining high strength and good ductility is a long-standing and challenging goal for metallic materials in modern engineering applications. Recently developed single-phase high and medium-entropy alloys, particularly those featuring heterogeneous microstructures, demonstrate superior strength-ductility synergy. Here, a single-phase CrCoNi-based medium-entropy alloy (MEA) with heterogeneous microstructures is introduced through suitable thermo-mechanical treatment. The analysis systematically examines the development of heterogeneous microstructures and their corresponding mechanical properties. The tailored CrCoNi-based MEA demonstrated an exceptional balance between strength and ductility, with a yield stress of approximately 1160 MPa and fracture elongation of 29.3% at annealing 800 ℃ for 1 h. The analysis reveals heterogeneous microstructures consisting of variously sized deformed grains, recovery substructure, recrystallized grains, and annealing twins. These features are primarily influenced by the initial grain size, deformation texture, cold-rolling reduction, and annealing temperature. Elevated annealing temperatures enhance the transformation trend of the microbands, introduced by cold rolling, into recrystallized grains. These findings not only provide a fundamental understanding of the formation mechanisms of the heterogeneous microstructure but also useful guidance for developing methods to tailor microstructures in high and medium-entropy alloys.

Complex-concentrated alloys (CCAs) have received a lot of attention recently due to their exceptional balance between strength and ductility. In this work, a brittle intermetallic compound strengthening Ni46.3Fe21Cr18.5Al10V4.2 (at. %) CCA has fabricated via carefully two-step thermomechanical treatment. The microstructure, phase composition, and mechanical properties of this alloy were investigated systematically. The microstructure characterization that brittle dual-morphology B2 particles are major second phases for the alloy under the two-step heat treatment. The microstructure characterization reveals that the coarse spherical B2 intermetallic compounds pinned grain boundaries and the dispersed dual-morphology B2 intermetallic compounds in the FCC matrix are key factors contributing to excellent mechanical properties. The yield strength and ultimate strength of the CCA enhanced substantially from 920 MPa and 1230 MPa in the annealed state, respectively, to 1400 MPa and 1660 MPa after aging treatment, while the uniform elongation remains above 18.5%. This work reveals the mechanical properties of the CCA can be enhanced by controlling B2 particles morphology and dispersion via suitable thermomechanical processing to meet the requirements of engineering J o u r n a l P r e-p r o o f 2 applications.

Complex-concentrated alloys (CCAs) have gained significant attention in recent years due to their exceptional combination of high strength and ductility. In this work, a novel Cr 18.5 Fe 21 Ni 46.3 V 4.2 Al 10 (at. %) CCA was designed and prepared. The dual-precipitates microstructures with hard B2 precipitates and coherent L1 2 nanoprecipitates, which provide a synergic strength-ductility effect, were introduced into a Cr 18.5 Fe 21-Ni 46.3 V 4.2 Al 10 CCA through appropriate thermomechanical processing strategy. By severe cold rolling and one-step annealing of 1 h at 900 • C, the CCA exhibits a yield strength of 920 MPa, a tensile strength of 1230 MPa, and a uniform elongation of 23.8 %. Microstructure analysis revealed that the excellent mechanical properties are primarily due to coherent L1 2 nanoprecipitates being sheared by abundant stacking faults, which facilitates dislocation gliding and enhances the strain-hardening capability and ductility. However, the hard B2 precipitates have two different deformation mechanisms. On the one hand, the B2 precipitates are bypassed by dislocations, leading to the dislocation pileups against the interface between the B2 precipitates and the FCC matrix, which increases the strain hardening capability but induces stress concentrations. On the other hand, the B2 precipitates provide fine grain strengthening by hindering grain growth. Additionally, dual-precipitation phases also interact significantly with other crystal defects, such as dislocations, stacking faults, and nano twins. Our results demonstrate that the dual-precipitates microstructure is an effective strategy to achieve CCAs or other alloys with high strength-ductility balance.