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<p>This study investigates the effect of initial dislocation density on the ballistic penetration resistance of high-strength steels (HSSs) for armor application. Two HSSs with identical chemical composition and prior austenite grain size (~&#xa0;8.0 to 8.1&#xa0;<i>μ</i>m) but distinct dislocation densities and retained austenite contents were compared. Ballistic tests showed that the sample with higher initial dislocation density (#2) effectively resisted projectile penetration, while the sample #1 with low dislocation density was penetrated. Microstructure characterization <i>via</i> SEM, EBSD, and TEM revealed that sample #1 was strengthened mainly by high-density nano-precipitates with low initial dislocation density, whereas sample #2 was dominated by high dislocation density strengthening. EBSD and XRD verified that sample #2 possessed higher initial retained austenite (RA) content (1 pct) than sample #1 (0.4 pct), and the RA content in the impact crater of sample #2 decreased to 0.4 pct, confirming the occurrence of stress-induced martensitic transformation (TRIP effect). Texture and grain boundary distributions were similar in both steels, ruling out their influence on ballistic performance differences. Constitutive model extrapolation indicated that sample #2 exhibited higher flow stress and work-hardening capacity over a wide range of plastic strain. The superior ballistic performance of sample #2 originates from the synergy of high initial dislocation density and localized TRIP effect: the dense dislocation network provides strong deformation resistance and promotes dislocation pile-ups to lower the critical condition for martensitic transformation. This “high dislocation-density-dominated + localized-TRIP-effect-assisted” synergistic mechanism efficiently dissipates impact energy, delays plastic instability and adiabatic shear band formation, and significantly improves penetration resistance under ultra-high-strain-rate ballistic impact. The results demonstrate that tailoring initial dislocation density is more effective than relying solely on nano-precipitation strengthening for armor steel design, providing a new strategy for developing next-generation ballistic steels with balanced ultra-high strength and dynamic toughness.</p>

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A Study of Initial Dislocation Density on Ballistic Performance of High-Strength Steels for Armor Application

  • 期刊论文

  • 发表日期：

    2026年5月20日

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  • Kejian Li

摘要

This study investigates the effect of initial dislocation density on the ballistic penetration resistance of high-strength steels (HSSs) for armor application. Two HSSs with identical chemical composition and prior austenite grain size (~ 8.0 to 8.1 μm) but distinct dislocation densities and retained austenite contents were compared. Ballistic tests showed that the sample with higher initial dislocation density (#2) effectively resisted projectile penetration, while the sample #1 with low dislocation density was penetrated. Microstructure characterization via SEM, EBSD, and TEM revealed that sample #1 was strengthened mainly by high-density nano-precipitates with low initial dislocation density, whereas sample #2 was dominated by high dislocation density strengthening. EBSD and XRD verified that sample #2 possessed higher initial retained austenite (RA) content (1 pct) than sample #1 (0.4 pct), and the RA content in the impact crater of sample #2 decreased to 0.4 pct, confirming the occurrence of stress-induced martensitic transformation (TRIP effect). Texture and grain boundary distributions were similar in both steels, ruling out their influence on ballistic performance differences. Constitutive model extrapolation indicated that sample #2 exhibited higher flow stress and work-hardening capacity over a wide range of plastic strain. The superior ballistic performance of sample #2 originates from the synergy of high initial dislocation density and localized TRIP effect: the dense dislocation network provides strong deformation resistance and promotes dislocation pile-ups to lower the critical condition for martensitic transformation. This “high dislocation-density-dominated + localized-TRIP-effect-assisted” synergistic mechanism efficiently dissipates impact energy, delays plastic instability and adiabatic shear band formation, and significantly improves penetration resistance under ultra-high-strain-rate ballistic impact. The results demonstrate that tailoring initial dislocation density is more effective than relying solely on nano-precipitation strengthening for armor steel design, providing a new strategy for developing next-generation ballistic steels with balanced ultra-high strength and dynamic toughness.