Probing the local atomic structure of Sr-modified Al-Si alloys

P. Srirangam; S. Chattopadhyay; A. Bhattacharya; S. Nag; J. Kaduk; S. Shankar; R. Banerjee; T. Shibata

doi:10.1016/j.actamat.2013.10.060

Probing the local atomic structure of Sr-modified Al-Si alloys

P. Srirangam, S. Chattopadhyay, A. Bhattacharya, S. Nag, J. Kaduk, S. Shankar, R. Banerjee, T. Shibata

Research output: Contribution to journal › Article › peer-review

94 Scopus citations

Abstract

Extended X-ray absorption fine structure (EXAFS) spectroscopy and atom probe tomography (APT) measurements were jointly used for the first time to probe the local structure around Sr atoms in Al-10%Sr master alloy and in Al-3%Si-0.04%Sr and Al-12.5%Si-0.04%Sr eutectic alloys in order to study the impact of trace levels of Sr on the morphological changes occurring in Al-Si binary eutectic alloy. EXAFS analysis shows the oxidation states of Sr is close to Sr⁰ in all the alloys studied. In the Al-10%Sr master alloy, Sr atoms tend to form the intermetallic compound Al₄Sr. On the other hand, in Al-Si alloys, Sr atoms segregate towards Si-rich regions, preferentially bonding to Si atoms to form Al₂Si₂Sr-like clusters with a coordination environment consistent with bulk Al ₂Si₂Sr. APT study reveals the presence of nanometer-sized Al-rich and Si-rich regions and support the EXAFS results. We speculate that addition of trace levels of Sr to Al-Si binary alloy system results in the initial formation of Al₂Si₂Sr-like clusters and the presence of such intermetallic clusters could play an important role such as poisoning of nucleation sites, thereby delaying the nucleation of eutectic phases and causing the morphological changes of the eutectic phases in the Al-Si alloys.

Original language	English
Pages (from-to)	185-193
Number of pages	9
Journal	Acta Materialia
Volume	65
DOIs	https://doi.org/10.1016/j.actamat.2013.10.060
State	Published - Feb 15 2014
Externally published	Yes

Funding

MRCAT operations are supported by the Department of Energy and the MRCAT member institutions. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Authors would like to thank Dr. Jeffrey T. Miller of Argonne National Laboratory for fruitful discussions, Prof. Carlo Segre of Illinois Institute of Technology for support of this research by allocating staff time to beamline scientists; and Dr. Vladislav Zyryanov for his help during the experiments. We thank Dr. Shelly Kelly of EXAFS analysis Inc., USA for her valuable suggestions during EXAFS data analysis.

Keywords

Al-Si alloys
Atom probe tomography
Sr modification
X-ray absorption spectroscopy
X-ray diffraction

Access to Document

10.1016/j.actamat.2013.10.060

Cite this

@article{b5c106a57b94431d8e58d5b3d1d9265f,

title = "Probing the local atomic structure of Sr-modified Al-Si alloys",

abstract = "Extended X-ray absorption fine structure (EXAFS) spectroscopy and atom probe tomography (APT) measurements were jointly used for the first time to probe the local structure around Sr atoms in Al-10%Sr master alloy and in Al-3%Si-0.04%Sr and Al-12.5%Si-0.04%Sr eutectic alloys in order to study the impact of trace levels of Sr on the morphological changes occurring in Al-Si binary eutectic alloy. EXAFS analysis shows the oxidation states of Sr is close to Sr0 in all the alloys studied. In the Al-10%Sr master alloy, Sr atoms tend to form the intermetallic compound Al4Sr. On the other hand, in Al-Si alloys, Sr atoms segregate towards Si-rich regions, preferentially bonding to Si atoms to form Al2Si2Sr-like clusters with a coordination environment consistent with bulk Al 2Si2Sr. APT study reveals the presence of nanometer-sized Al-rich and Si-rich regions and support the EXAFS results. We speculate that addition of trace levels of Sr to Al-Si binary alloy system results in the initial formation of Al2Si2Sr-like clusters and the presence of such intermetallic clusters could play an important role such as poisoning of nucleation sites, thereby delaying the nucleation of eutectic phases and causing the morphological changes of the eutectic phases in the Al-Si alloys.",

keywords = "Al-Si alloys, Atom probe tomography, Sr modification, X-ray absorption spectroscopy, X-ray diffraction",

author = "P. Srirangam and S. Chattopadhyay and A. Bhattacharya and S. Nag and J. Kaduk and S. Shankar and R. Banerjee and T. Shibata",

year = "2014",

month = feb,

day = "15",

doi = "10.1016/j.actamat.2013.10.060",

language = "English",

volume = "65",

pages = "185--193",

journal = "Acta Materialia",

issn = "1359-6454",

publisher = "Elsevier",

}

TY - JOUR

T1 - Probing the local atomic structure of Sr-modified Al-Si alloys

AU - Srirangam, P.

AU - Chattopadhyay, S.

AU - Bhattacharya, A.

AU - Nag, S.

AU - Kaduk, J.

AU - Shankar, S.

AU - Banerjee, R.

AU - Shibata, T.

PY - 2014/2/15

Y1 - 2014/2/15

N2 - Extended X-ray absorption fine structure (EXAFS) spectroscopy and atom probe tomography (APT) measurements were jointly used for the first time to probe the local structure around Sr atoms in Al-10%Sr master alloy and in Al-3%Si-0.04%Sr and Al-12.5%Si-0.04%Sr eutectic alloys in order to study the impact of trace levels of Sr on the morphological changes occurring in Al-Si binary eutectic alloy. EXAFS analysis shows the oxidation states of Sr is close to Sr0 in all the alloys studied. In the Al-10%Sr master alloy, Sr atoms tend to form the intermetallic compound Al4Sr. On the other hand, in Al-Si alloys, Sr atoms segregate towards Si-rich regions, preferentially bonding to Si atoms to form Al2Si2Sr-like clusters with a coordination environment consistent with bulk Al 2Si2Sr. APT study reveals the presence of nanometer-sized Al-rich and Si-rich regions and support the EXAFS results. We speculate that addition of trace levels of Sr to Al-Si binary alloy system results in the initial formation of Al2Si2Sr-like clusters and the presence of such intermetallic clusters could play an important role such as poisoning of nucleation sites, thereby delaying the nucleation of eutectic phases and causing the morphological changes of the eutectic phases in the Al-Si alloys.

AB - Extended X-ray absorption fine structure (EXAFS) spectroscopy and atom probe tomography (APT) measurements were jointly used for the first time to probe the local structure around Sr atoms in Al-10%Sr master alloy and in Al-3%Si-0.04%Sr and Al-12.5%Si-0.04%Sr eutectic alloys in order to study the impact of trace levels of Sr on the morphological changes occurring in Al-Si binary eutectic alloy. EXAFS analysis shows the oxidation states of Sr is close to Sr0 in all the alloys studied. In the Al-10%Sr master alloy, Sr atoms tend to form the intermetallic compound Al4Sr. On the other hand, in Al-Si alloys, Sr atoms segregate towards Si-rich regions, preferentially bonding to Si atoms to form Al2Si2Sr-like clusters with a coordination environment consistent with bulk Al 2Si2Sr. APT study reveals the presence of nanometer-sized Al-rich and Si-rich regions and support the EXAFS results. We speculate that addition of trace levels of Sr to Al-Si binary alloy system results in the initial formation of Al2Si2Sr-like clusters and the presence of such intermetallic clusters could play an important role such as poisoning of nucleation sites, thereby delaying the nucleation of eutectic phases and causing the morphological changes of the eutectic phases in the Al-Si alloys.

KW - Al-Si alloys

KW - Atom probe tomography

KW - Sr modification

KW - X-ray absorption spectroscopy

KW - X-ray diffraction

UR - http://www.scopus.com/inward/record.url?scp=84902589496&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2013.10.060

DO - 10.1016/j.actamat.2013.10.060

M3 - Article

AN - SCOPUS:84902589496

SN - 1359-6454

VL - 65

SP - 185

EP - 193

JO - Acta Materialia

JF - Acta Materialia

ER -

Probing the local atomic structure of Sr-modified Al-Si alloys

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this