Partial pair correlation functions and viscosity of liquid Al–Si hypoeutectic alloys via high-energy X-ray diffraction experiments

X-ray nano-diffraction study of Sr intermetallic phase during solidification of Al-Si hypoeutectic alloy

“…2 There are two schools of thought in explaining the mechanism of modification of the eutectic phases by Sr addition: the poisoning of the Twin Plane Re-entrant Edge (TPRE) in the growth of the eutectic Si phase by Sr atoms [3][4][5][6] and recently, the role of Sr in significantly altering the nucleation of intermetallic and eutectic phases during solidification by altering the atomic structure of the inter-dendritic liquid alloy. [7][8][9] The mechanism of Sr poisoning the TPRE growth mode of the eutectic Si phase relies on trace elemental additions to the Al-Si alloy melt such that the ideal atomic radius ratio between the modifier element and silicon is around 1.65. 5 However, this mechanism did not explain the effectiveness of several elements that fit this radius ratio and vice-versa, for example, Yb (ratio of 1.66) was not able to modify Si while Na (ratio of 1.59) was able to effectively modify Si under similar conditions.…”

“…The latter school of thought seems to be far more substantiated with experimental evidences and mechanistic theories. In our recent efforts, 7,8,[19][20][21] several research outcome have been published to substantiate that Sr addition significantly alters the nucleation environment of several secondary phases such as the Fe bearing intermetallic and eutectic phases during solidification; in this publication, the AlSiSr intermetallic phase has been analyzed using the nano-diffraction technique with a high energy synchrotron beam source coupled with x-ray fluorescence imaging system to show that the Sr only evolves as AlSiSr intermetallic phase at the eutectic temperature, predominantly as the Al 2 Si 2 Sr phase. In this publication, all the elemental levels in the alloys mentioned are in weight percentage unless otherwise mentioned.…”

“…A typical XRD spectrum obtained from Al-7Si-0.05Fe-0.03Sr alloy at (3,8) Figure 3(a) is shown in Figure 4. The images of diffraction rings were obtained with constant exposure time of 20 s at three fixed inclinations of CCD camera (28 , 43 , and 58 ), then integrated and processed to obtain the resultant spectrum (intensity versus 2h).…”

Ab initio molecular dynamics simulation of self-diffusion in Al–Si binary melts

“…A similar performance of the exchange correlation functionals is found in the case of predicted densities of Al-12 at% Si (figure 1(b)). In comparison to the experimental data reported by Srirangam et al [18], LDA overestimates the density by 5.3% while GGA(PBE) underestimates it by 1.3%. Figure 1(c) shows the liquid densities, which are predicted by employing GGA(PBE) functional, at different compositions.…”

“…In the liquid with 12 at% Si, however, the GGA(PBE)-predicted density at T<1200 K deviates from a linear fit of the higher temperatures (figure 1(b)). Srirangam et al [18], employing high energy x-ray diffraction, investigated Al-Si liquids and reported density of the Al-12.07 at% Si liquid in the range of 867-1065 K. Their reported [17] and Srirangam et al [18], respectively. The temperature dependence of the GGA(PBE)-predicted densities of Al-12 at% Si liquid exhibits a deviation from a linear fit at T<1200 K and the solid fit line of these densities is obtained by fitting the data from 1200 to 1800 K to demonstrate the deviation.…”