AC4Cアルミニウム合金の組織に及ぼす凝固条件の影響

抄録

Equiaxed and columnar structures are formed in lower and upper ends and in other parts of unidirectionally solidified castings respectively. This structural difference depends on constitutional supercooling parameters. Fine particles of Si are formed by eutectic reaction at cooling velocities above 1°C/s. Rod-like Si crystallizes at lower cooling velocities. As for T6 treated castings, the tip of Si crystals is rounded, but still remains a rod-like form in the castings solidified at lower cooling velocities. Primary and secondary dendrite arm spacings shorten with increasing these solidification parameters. Correlations of V_LC (cooling velocity in liquid state)and DAS1 (primary dendrite arm spacing)and Of V_S4C (partial cooling velocity from liquidus to the temperature at which 40% volume fraction of solid solidifies) and DAS2 (secondary dendrite arm spacing) in the columnar structure have the maximum correlation coefficient as: DAS1=305V^-0.520_LC and DAS2=34.8V^-0.350_S4C.