沉淀硬化不锈钢FV520(B)的析出硬化及韧性

采用透射电镜试验、硬度试验和示波冲击试验等方法，研究时效对沉淀硬化不锈钢FV520(B)组织和性能的影响。结果表明，时效过程中，FV520(B)钢主要以富铜相ε-Cu析出为主。硬度在420 ℃时效时出现峰值，主要与组织中细小富铜相共格析出有关。随着时效温度增加，富铜相逐步脱溶长大，基体再结晶，使其硬化程度逐步降低。FV520(B)钢的韧性主要决定于冲击裂纹扩展功。时效组织对FV520(B)钢冲击裂纹萌生功影响较小，对裂纹扩展功有着较大的影响。420 ℃时效时FV520(B)钢韧性最差，而600 ℃时效时韧性最好。420、470 ℃时效状态下的冲击试样扩展区断口以解理形貌为主，而其他时效状态下为韧窝，但韧窝细节各不相同。

PRECIPITATION-HARDENING AND TOUGHNESS OF PRECIPITATION- HARDENING STAINLESS STEEL FV520(B)

By transmission electron microscope, hardenss test and instrumented impact test, the effect of aging process on microstructure and properties of precipitation-hardening stainless steel FV520(B) is investigated. The results show that the most precipitate of FV520(B) steel is copper-rich phase ε-Cu. The maximum hardness is reached after FV520(B) ages at 420 ℃, due to the coherent precipitation of fine copper particles. However, the hardness of FV520(B) aged at higher than 420 ℃ gradually decreases , due to the ε-Cu precipitating and coarsening, the matrix recrystallizing. Toughness of FV520(B) at different aging temperatures is dependent on the crack propagation energy. The effect of aging microstructure on impact crack initiation energy is less, but the effect of that on crack propagation energy is great. As FV520(B) aged at 420 ℃ and 600 ℃, its toughness is the worst and best respectively. The fracture appearance of the impact specimens aged at 420 ℃ and 470 ℃ mostly is in form of cleavage, which of the specimens aged at other temperature mostly in form of dimple, but the dimples have nice difference.