Macrostructural and microstructural development in Al–Si alloys directionally solidified under unsteady-state conditions

Influence of upward and horizontal growth direction on microstructure and microhardness of an unsteady-state directionally solidified Al-Cu-Si alloy

“…It is observed in Figures 6a and 6b that power laws equal to -1.1 and -0.55 characterize the experimental variation of primary spacing with growth rate and cooling rate, respectively, i.e, λ1 = 96(VL) -1.1 and λ1 = 396(TR) -0.55 . This is in agreement with observations reported by ROCHA et al [10], PERES et al [5], CARVALHO et al [7], CRUZ et al [15] BARROS et al [13] COSTA et al [12] and GOMES [16] that exponential relationships and λ1 = constant(VL) -1.1 and λ1 = constant(TR) -0.55 best generate the experimental variation of primary dendritic arms with VL and TR along the unsteady-state solidification of Al-Cu, Al-Si, Al-Sn, Al-Cu, Al-Cu-Si and Al-Cu-Si alloys, respectively. With a view to analyzing the effect of Si element in binary Al-3wt.% Cu alloy as well as the influence of growth direction on the length scale of the dendritic microstructure (1) the average, maximum and minimum values of the correlation between 1 and TR of this work are plotted in Figure 7 and compared with the experimental equations obtained by BARROS et al [13] and GOMES [16], whose works have been developed to horizontal and upward directional solidification, respectively.…”

“…Nowadays these alloys are supplied in a wide range of chemical compositions [1][2][3][4][5][6][7][8][9][10][11][12]. We highlight the Al-Cu-Si ternary system because of particular outstanding properties such as high mechanical strength, low weight and very good fluidity [3][4][5][6][7][8][9][10][11][12].…”

Transient Directional Solidification of Cast Iron: Microstructure Formation, Columnar to Equiaxed Transition and Hardness

“…According to this list in table 1, it seems that cooling rate is not sensitive to the position of the CET. On the other hand, the response of The thermal CET criteria are recognized as very good indicative for the macrostructural transition as reported in several articles [12][13][14]17,18 . However, none previous study has been found on determining the solidification thermal parameters associated with the CET of cast iron.…”

“…However, none previous study has been found on determining the solidification thermal parameters associated with the CET of cast iron. In the case of Sn-based 12,13,19 and Al-based 14,17,18 alloys investigations have been addressed to single-phase and hypoeutectic alloys. In these cases, critical cooling rate was established as a realistic criterion, since cooling rate (Ṫ) encompasses growth rate (V) and temperature gradient (G), i.e., =G x v. The present investigation deals with a eutectic alloy and in this case it appears that a critical growth rate of about 0.6mm/s is adequate criteria for cast iron.…”

“…Svidró and Diószegi 10 stated that there are limited known investigation methods to determine CET in cast iron and consequently there is no information on how metallurgical parameters are affecting its occurrence. Investigations on vertically upward directional solidification of Al-Cu, Al-Si and Sn-Pb alloys have proposed a CET criteria based on critical cooling rates of about 0.2 K/s, 0.17 K/s and 0.014 K/s, respectively, with the columnar growth prevailing throughout the casting for cooling rates higher than these critical values [12][13][14] . The application of such criterion based on a critical solidification thermal parameter has never been verified considering data from solidification of cast iron.…”