Tohoku University · Engineering
Professor Yongjie Zhang's research lab specializes in the microstructural design and mechanical property optimization of advanced low-carbon steels, with a focus on nano-alloy carbide precipitation mechanisms. The lab investigates interphase precipitation and tempering behaviors in microalloyed steels to enhance strength and toughness, particularly through the controlled formation of fine, coherent carbides. Utilizing advanced characterization techniques such as three-dimensional atom probe tomography and quantitative microstructural analysis, the lab explores the effects of alloying elements (V, Nb, Ti, N) and processing parameters on precipitation kinetics and mechanical performance. Their work bridges fundamental materials science with industrial applications, especially in high-performance structural materials for transportation and energy sectors.
Figures are computed from collected data and may differ slightly.
Fused filament fabrication (FFF) is increasingly adopted for direct manufacturing of end use parts in an aviation industry. However, the application of FFF technique is still restricted to manufacturing low criticality lightly loaded parts, due to poor mechanical performance. To alleviate the mechanical performance issue, thermal annealing process is frequently utilized. However, problems such as distortion issues and the need for jigs and fixtures limit the effectiveness of the thermal annealin
Abstract The current understanding of the microstructural features and mechanical properties of micro-alloyed low carbon steels strengthened by interphase precipitation of nano-sized alloy carbides are critically reviewed in this paper. The experimental results obtained via advanced quantitative characterization have revealed that interphase precipitation is promoted at the ferrite/austenite interface with a relatively lower degree of coherency caused by the deviation from the exact Kurdjumov–Sa
The resistance to temper softening in low carbon martensite with its underlying origin, by microalloying of strong carbide-forming alloying elements (V, Nb and Ti) to an Fe-0.1C-1.5Mn-0.05Si (mass%) alloy, was investigated in this study. With similar hardness in as-quenched condition in all the alloys used, the hardness of tempered martensite is increased by V, Nb and Ti additions, particularly after treatment at higher temperature with longer time. The increment in hardness becomes larger by mo
The composition of nano-sized alloy carbides formed by interphase precipitation in V-Nb and V-Ti multiple microalloyed low-carbon steels is analyzed by using three-dimensional atom probe. Carbide-forming alloying elements including V, Nb, and Ti, are simultaneously precipitated from the early stage of isothermal treatment, whose atoms are uniformly distributed in the carbide particles, even after prolonged holding. Cluster analysis by the maximum separation method, with parameters optimized usin
Interphase precipitation of nano-sized alloy carbides is recently used to strengthen low carbon steels for its excellent contributions to strength and formability. The effects of nitrogen addition on the hardness of vanadium-microalloyed low carbon steels were investigated by considering both the dispersion of interphase precipitation and the ferrite/austenite crystallography. Three-dimensional atom probe analysis reveals that interphase precipitation of vanadium carbide is hardly affected by in
The precipitation of nano-sized alloy carbides in steels with a large amount of strengthening can be obtained by conventional tempering of martensite or interphase precipitation occurring during isothermal ferrite transformation. In this study, a vanadium-microalloyed low carbon steel with a composition of Fe-0.1C-0.4V-1.5Mn-0.05Si (mass%) was either isothermally transformed or quenched and tempered at 923 K for various periods, to comparatively investigate the precipitation behaviors of vanadiu
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