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The primary dendrite morphology and spacing of DZ125 superalloy have been observed during directional solidification under high thermal gradient about 500 K/cm.The results reveal that the primary dendrite arm spacing decreases from 94μm to 35.8μm with the increase of directional solidification cooling rate from 2.525 K/s to 36.4 K/s.The regression equation of the primary dendrite arm spacingsλ 1 versus cooling rate is λ 1 =0.013(GV)-0.32.The predictions of Kurz/Fisher model and Hunt/Lu model accord reasonably well with the experimental data.The influence of directional solidi fication rate under variable thermal gradient on the primary dendrite arm spacing has also been investigated.
The primary dendrite morphology and spacing of DZ125 superalloy have been observed during directional solidification under high thermal gradient about 500 K / cm. The results reveal that the primary dendrite arm spacing decreases from 94 μm to 35.8 μm with the increase of directional solidification cooling rate from 2.525 K / s to 36.4 K / s. The regression equation of the primary dendrite arm spacings λ 1 versus cooling rate is λ 1 = 0.013 (GV) -0.32. The predictions of Kurz / Fisher model and Hunt / Lu model accord reasonably well with the the experimental data. The influence of directional solidi fication rate under variable thermal gradient on the primary dendrite arm spacing has also been investigated.