The influence of time and temperature of ageing on the σ-phase morphology in ferritic-austenitic cast steel have been investigated in this study. The morphology and quantity of the σ-phase were analyzed by using optical microscope, X-ray diffractometry, scanning electron microscope and image analysis, respectively. The annealing temperature has a significant influence on the morphology, volume fraction and the dynamics of σ-phase precipitation. Surface development of the σ-phase decreases from R=4.3, for the cast steel annealed at 700°C to R=2.4 for the cast steel annealed at 900°C, and the volume fraction Vvσ from 50.8% to 26.5%, respectively. The most rapid progress of δ → σ + γ’ transformation was observed at 800°C.

UD C 539. 4 M ic r o s t r u c t u r a l a n d F r a c t u r e A n a ly s i s o f A g e d C a s t D u p le

I n f lu e n c e o f C a r b id e s M o r p h o l o g y o n F r a c t u r e T o u g h n e s s o f C a s t S t e e

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