Nucleation and growth of Fe-rich phases in Al-5Ti-1B modified Al-Fe alloys investigated using synchrotron X-ray imaging and electron microscopy

doi:10.1016/j.jmst.2020.12.011

Abstract

Abstract:

Plate-like Fe-rich intermetallic phases directly influence the mechanical properties of recycled Al alloys; thus, many attempts have been made to modify the morphology of these phases. Through synchrotron X-ray imaging and electron microscopy, the underlying nucleation and growth mechanisms of Fe-rich phases during the solidification of Al-5Ti-1B-modified Al-2Fe alloys were revealed in this study. The results showed that the Al-5Ti-1B grain refiner as well as the applied pressure both resulted in reduction of the size and number of primary Al₃Fe phases and promoted the formation of eutectic Al₆Fe phases. The tomography results demonstrated that Al-5Ti-1B changed the three-dimensional (3D) morphology of primary Fe-rich phases from rod-like to branched plate-like, while a reduction in their thickness and size was also observed. This was attributed to the fact that Ti-containing solutes in the melts inhibit the diffusion of Fe atoms and the Al₃Fe twins produce re-entrant corner on the twin boundaries along the growth direction. Moreover, the TiB₂ provides possible nucleation sites for Al₆Fe phases. The nucleation mechanism of Fe-rich phases is discussed in terms of experimental observations and crystallography calculations. The decrease in the lattice mismatch between TiB₂ and Al₆Fe phases was suggested, which promoted the transformation of Al₃Fe to Al₆Fe phases.

Key words: Al alloys, Synchrotron X-ray imaging, Fe-rich phases, Grain refinement, Nucleation and growth

Yuliang Zhao, Weiwen Zhang, Dongfu Song, Bo Lin, Fanghua Shen, Donghai Zheng, ChunXiao Xie, Zhenzhong Sun, Yanan Fu, Runxia Li. Nucleation and growth of Fe-rich phases in Al-5Ti-1B modified Al-Fe alloys investigated using synchrotron X-ray imaging and electron microscopy[J]. J. Mater. Sci. Technol., 2021, 80: 84-99.

Figures/Tables 20

Table 1 Alloy composition without and with grain refiner in this study (wt.%).

Alloy	Fe	Ti	V	B
Al-2Fe	1.97	0.001	0.004	-
Al-2Fe + 0.2 %Al-5Ti-1B	2.05	0.011	0.006	0.002

Fig. 1. (a) The deep-etched SEM images showing the Al3Ti and TiB2 particles in the Al-5Ti-1B master alloys; (b) the measured size distribution of TiB2 particles and their log-normal distribution fitting; the enlarge SEM images and composition of Al3Ti particles (c) and TiB2 particles (d).

Fig. 2. (a) Experimental setup used at beamline BL13W1 in SSRF; (b) schematic diagram of in-situ synchrotron X-ray radiography setup and sample arrangement.

Table 2 Synchrotron X-ray radiography and tomography parameters used at BL13W1, SSRF.

Experiment Parameters	In-situ X-ray radiography	X-ray tomography
X-ray Beam	monochromatic, 20 keV	monochromatic, 20 keV
Scintillator	Optique Peter	Optique Peter
Detector	Hamamatsu Orca Flash 4.0 v3	Hamamatsu Orca Flash 4.0 v3
Effective pixel size	0.65 μm and 6.5 μm	0.65 μm
Detector area	2048 × 2048 pixels 2048 × 700 pixels	2048 × 2048 pixels
Exposure Time	500 ms	300 ms
Magnification	1 × and 10 ×	10 ×
No. of Projections	1200	1200
Sample-to-Scintillator distance	1000 mm	200 mm

Fig. 3. SEM images and tomoscans of Fe-rich phases in the Al-2Fe alloys with different Al-5Ti-1B grain refiner and applied pressures: (a-b) NGR-NAP; (c-d) NGR-AP; (e-f) GR-NAP; (g-h) GR-AP.

Table 3 Chemical composition of Fe-rich phases in different alloys.

Alloys	Alloy compositions		Identified Phases
Alloys	Al	Fe	Identified Phases
NGR-NAP	78.0 ± 0.5	22.0 ± 0.9	Al₃Fe
NGR-AP	84.7 ± 0.9	15.3 ± 0.7	Al₃Fe
NGR-AP	88.9 ± 0.8	11.1 ± 0.3	Al₆Fe
GR-NAP	83.3 ± 0.7	16.7 ± 0.4	Al₃Fe
GR-NAP	89.3 ± 0.3	10.7 ± 0.8	Al₆Fe
GR-AP	81.6 ± 0.3	18.4 ± 0.4	Al₃Fe
GR-AP	92.0 ± 0.9	8.0 ± 0.3	Al₆Fe

Fig. 4. Deep-etched morphology of Fe-rich phases in the Al-2Fe alloys with different conditions: (a-c) NGR-NAP; (d-f) NGR-AP; (g-i) GR-NAP; (j-l) GR-AP.

Fig. 5. (a) Typical 3D morphology of Fe-rich phases in Al-2Fe alloy without Al-5Ti-1B; (b) EDS analysis of point 1 and 2 in.(a); (c) X-ray diffraction patterns of Al-2Fe alloy without Al-5Ti-1B under 0 MPa and 100 MPa.

Fig. 6. EBSD images showing the grain size of Al-2Fe alloys with different conditions: (a) NGR-NAP; (b) NGR-AP; (c) GR-NAP; (d) GR-AP; SEM image (e) and Kikuchi pattern of Al3Fe (f) and Al6Fe (g) in GR-NAP alloy.

Fig. 7. (a) A SEM images of primary Al3Fe in Al-2Fe alloy; (b) EBSD images of Al3Fe phases and Al matrix; (c) An inverse pole figure of twinned Al3Fe phases.

Fig. 8. In-situ synchrotron X-ray radiography showing the growth of Fe-rich phases in Al-2Fe alloy during solidification.

Fig. 9. Solidification sequence of the growth of primary Fe-rich phases in Al-2Fe alloy with 10 times lens.

Fig. 10. In-situ synchrotron X-ray radiography showing the growth of Fe-rich phases in the 0.2 % Al-5Ti-1B inoculated Al-2Fe alloy during solidification.

Fig. 11. In-situ synchrotron X-ray radiography showing the growth of Fe-rich phases in the 0.2 % Al-5Ti-1B inoculated Al-2Fe alloy during solidification with 10 times lens.

Fig. 12. 3D morphology and thickness of primary Fe-rich phases in Al-2Fe alloy: (a, b) NGR-NAP; (c, d) NGR-AP; (e, f) GR-NAP; (g, h) GR-AP; Typical single 3D morphology of primary Fe-rich phases: (h) plate-like; (i, j) rod-like; (k) cross-like.

Table 4 Volume statistics of primary Al3Fe obtained from synchrotron X-ray tomography in different alloys.

Alloys	Area (μm²)	Volume (μm³)	Specific surface area (μm^-1)
NGR-NAP	1,002,003	913,869	1.09
NGR-AP	664,976	639,615	1.03
GR-NAP	703,866	774,337	0.91
GR-AP	587,674	703,961	0.83

Fig. 13. (a) SEM image showing the possible nucleation sites for Fe-rich phases in Al-2Fe alloy with Al-5Ti-1B; (b) EDS mapping analysis confirming Ti-rich phases inside Fe-rich phase; (c) cross-section of thin foil after milled by FIB; (d) EDX mapping of the of thin foil; (e, f) bright-field TEM micrograph obtained in [101]Al zone axis showing the Al/Al6Fe interface in region A; (g) inverse FFT of Al matrix and corresponding diffraction pattern.

Fig. 14. (a) TEM image taken from region c in Fig. 12c, showing the TiB2/Al/Al6Fe interface; (b) HRTEM image obtained in [001]Al zone axis showing the orientation relationship of Al/TiB2 interface and corresponding diffraction patterns; (c) HRTEM image of Al6Fe/TiB2 interface and the diffraction pattern of Al6Fe phases; (d) HADDF micrograph showing the TiB2/Al/Al6Fe interface; (e) EDX mapping of the TiB2/Al/Al6Fe interface; (f, g) EDX line scanning of the TiB2/Al/Al6Fe interface.

Fig. 15. Length and width of primary Al3Fe phases in Al-2Fe alloys (a) without Al-5Ti-1B and (c) with Al-5Ti-1B vs solidification time; the growth rate of primary Al3Fe phases in Al-2Fe alloys (b) without Al-5Ti-1B and (d) with Al-5Ti-1B vs solidification time; (e) the total number of primary Al3Fe in both alloys vs solidification time.

Fig. 16. Interplanar spacing misfit between TiB2 and Fe-rich phases: (a) TiB2 and Al3Fe; (b) TiB2 and Al6Fe.

References 65

[1]	J.G. Kaufman, E.L. Rooy, Aluminum Alloy Castings: Properties, Processes, and Applications, ASM International, Materials Park, OH, 2004.
[2]	N.A. Belov, A.A. Aksenov, D.G. Eskin, Iron in Aluminum Alloys: Impurity and Alloying Element, CRC Press, London, 2002.
[3]	J.A.S. Green, Aluminum Recycling and Processing for Energy Conservation and Sustainability, ASM International, Materials Park, OH, 2007.
[4]	L.F. Zhang, J.W. Gao, L.N.W. Damoah, D.G. Robertson, Mine. Process. Extr. M. 33 (2012) 99-157.
[5]	X.L. Li, A. Scherf, M. Heilmaier, F. Stein, J. Phase Equilib. Diff. 37 (2016) 162-173. DOI URL
[6]	D. Liang, P. Korgul, H. Jones, Acta Mater. 44 (1996) 2999-3004. DOI URL
[7]	C.A. Ahravct, M.Ö. Pekguleryüz, Calphad 22 (1998) 147-l55. DOI URL
[8]	P.R. Goulart, K.S. Cruz, J.E. Spinelli, I.L. Ferreira, N. Cheung, A. Garcia, J. Alloys. Compd. 470 (2009) 589-599. DOI URL
[9]	Y.H. Liang, Z.M. Shi, G.W. Li, R.Y. Zhang, G. Zhao, J. Alloys. Compd. 781 (2019) 235-244. DOI URL
[10]	Y.H. Liang, Z.M. Shi, G.W. Li, R.Y. Zhang, M. Li, Mater. Res. Express 6 (2019), 106504.
[11]	X. Wang, R.G. Guan, Y. Wang, R.D.K. Misra, B.W. Yang, Y.D. Li, T.J. Chen, Mater. Sci. Eng. A 751 (2019) 23-34. DOI URL
[12]	J.P. Hou, R. Li, Q. Wang, H.Y. Yu, Z.J. Zhang, Q.Y. Chen, H. Ma, X.W. Li, Z.F. Zhang, Materialia 7 (2019), 100403. DOI URL
[13]	B. Lin, W.X. Zhang, X.P. Zheng, Y.L. Zhao, Z.H. Lou, W.W. Zhang, Mater. Charact. 150 (2019) 128-137. DOI
[14]	X.Z. Zhu, P. Blake, K. Dou, S.X. Ji, Mater. Sci. Eng. A 732 (2018) 240-250. DOI URL
[15]	Z.M. Shi, K. Gao, Y.T. Shi, Y. Wang, Mater. Sci. Eng. A 632 (2015) 62-71. DOI URL
[16]	A. Duchaussoy, X. Sauvage, K. Edalati, Z. Horita, G. Renou, A. Deschamps, F.D. Geuser, Acta Mater. 167 (2019) 89-102. DOI
[17]	Z. Fan, Y. Wang, Y. Zhang, T. Qin, X.R. Zhou, G.E. Thompson, T. Pennycook, T. Hashimoto, Acta Mater. 84 (2015) 292-304. DOI URL
[18]	M.A. Easton, M. Qian, A. Prasad, D.H. StJohn, Curr.Opin. St. M. 20 (2016) 13-24.
[19]	L. Zhou, F. Gao, G.S. Peng, N. Alba-Baena, J. Alloys. Compd. 689 (2016) 401-407. DOI URL
[20]	E.Z. Wang, T. Gao, J.F. Nie, X.F. Liu, J. Alloys. Compd. 594 (2014) 7-11. DOI URL
[21]	J. Santos, L.H. Kallien, A.E.W. Jarfors, A.K. Dahle, Metall. Mater. Trans. A 47 (2016) 4080-4091. DOI URL
[22]	H.G. Wei, F.Z. Xia, M.P. Wang, Mater. Sci. Eng. A 682 (2017) 1-11. DOI URL
[23]	A.B. Pattnaika, S. Dasa, B.B. Jhab, N. Prasantha, J. Mater. Res, Technol. 4 (2015) 171-179.
[24]	Q.L. Bai, Y. Li, H.X. Li, Q. Du, J.S. Zhang, L.Z. Zhuang, Metall. Mater. Trans. A 47 (2016) 4080-4091. DOI URL
[25]	Z.P. Que, Y. Wang, Y.P. Zhou, L. Liu, Z. Fan, Mater. Sci.Forum 828-829 (2015) 53-57.
[26]	J. Rakhmonov, G. Timelli, F. Bonollo, Int. J. Metalcast. 11 (2017) 294-304. DOI URL
[27]	S. Kumar, K.A.Q. O’Reilly, Mater.Charact. 120 (2016) 311-322.
[28]	S.H. Rodríguez, R.E.G. Reyes, D.K. Dwivedi, O.A. González, V.H.B. Hernández, Mater. Manuf. Process. 27 (2012) 599-604. DOI URL
[29]	Y. Li, B. Hu, B. Liu, A.M. Nie, Q.F. Gu, J.F. Wang, Q. Li, Acta Mater. 187 (2020) 51-65. DOI URL
[30]	Y. Li, Y. Jiang, B. Liu, Q. Luo, B. Hu, Q. Li, J. Mater. Sci. Technol. 65 (2021) 190-201. DOI URL
[31]	J. Xu, Y. Li, K. Ma, Y.N. Fu, E.Y. Guo, Z.N. Chen, Q.F. Gu, Y.X. Han, T.M. Wang, Q. Li, Scr. Mater. 187 (2020) 142-147. DOI URL
[32]	B. Dang, X. Zhang, Y.Z. Chen, C.X. Chen, H.T. Wang, F. Liu, Sci. Rep. 6 (2016) 30874. DOI PMID
[33]	M.W. Meredith, A.L. Greer, P.V. Evans, USA, 1998, pp. 977-982.
[34]	R. Cunningham, C. Zhao, N. Parab, C. Kantzos, J. Pauza, K. Fezzaa, T. Sun, A.D. Rollet, Science 363 (2019) 849-852. DOI PMID
[35]	H. Yasuda, K. Morishita, N. Nakatsuka, T. Nishimura, M. Yoshiya, A. Sugiyama, K. Uesugi, A. Takeuchi, Nat. Commun. 10 (2019) 3183. DOI URL
[36]	B. Wang, D.Y. Tan, T.L. Lee, J.C. Khong, F. Wang, D. Eskin, T. Connolley, K. Fezzaa, J.W. Mi, Acta Mater. 144 (2018) 505-515. DOI URL
[37]	E. Liotti, C. Arteta, A. Zisserman, A. Lui, V. Lempitsky, P.S. Grant, Sci. Adv. 4 (2018), eaar4004.
[38]	S. Feng, E. Liotti, A. Lui, S. Kumar, A. Mahadevegowda, K.A.Q.O, Reilly, P.S. Grant, Scr.Mater. 149 (2018) 44-48.
[39]	A. Bjurenstedt, D. Casari, S. Seifeddine, R.H. Mathiesen, A.K. Dahle, Acta Mater. 130 (2017) 1-9. DOI URL
[40]	B. Cai, A. Kao, P.D. Lee, E. Boller, H. Basevi, A.B. Phillion, A. Leonardis, K. Pericieous, Scr. Mater. 165 (2019) 29-33. DOI URL
[41]	C. Puncreobutr, A.B. Phillion, J.L. Fife, P. Rockett, A.P. Horsfield, P.D. Lee, Acta Mater. 79 (2014) 292-303. DOI URL
[42]	J.M. Yu, N. Wanderka, A. Rack, R. Daudin, E. Boller, H. Markötter, A. Manzoni, F. Vogel, T. Arlt, I. Manke, J. Banhart, Acta Mater. 129 (2017) 194-202. DOI URL
[43]	S. Chuaypradit, C. Puncreobutr, A.B. Phillion, J.L. Fife, P.D. Lee, Quantifying the effects of grain refiner addition on the solidification of Fe-rich intermetallics in Al-Si-Cu alloys using in situ synchrotron X-ray tomography, TMS Annual Meeting & Exhibition TMS 2018: Light Metals (2018) 1067-1073.
[44]	R.C. Chen, D. Dreossi, L. Mancini, R. Menk, L. Rigon, T.Q. Xiao, R. Longo, J. Synchrotron Rad. 19 (2012) 836-845. DOI URL
[45]	Y. Zhao, W. Du, B. Koe, T. Connolley, S. Irvine, P.K. Allan, C.M. Schlepütz, W. Zhang, F. Wang, D.G. Eskin, J. Mi, Scr. Mater. 146 (2018) 321-326. DOI URL
[46]	Y.L. Zhao, Z. Wang, C. Zhang, W.W. Zhang, J. Alloys. Compd. 777 (2019) 1054-1065. DOI URL
[47]	Y.L. Zhao, D.F. Song, B. Lin, C. Zhang, D.H. Zheng, S. Inguva, T. Li, Z.Z. Sun, Z. Wang, W.W. Zhang, Mater. Charact. 153 (2019) 354-365. DOI URL
[48]	Y.L. Zhao, B. Lin, D.F. Song, D.H. Zheng, Z.Z. Sun, C.X. Xie, W.W. Zhang, Materials 12 (2019) 3904. DOI URL
[49]	L. Li, Y.D. Zhang, C. Esling, H.X. Jiang, Z.H. Zhao, Y.B. Zuo, J.Z. Cui, J. Appl. Crystallogr. 43 (2010) 1108-1112. DOI URL
[50]	W.W. Zhang, Y.L. Zhao, D.T. Zhang, Z.Q. Luo, C. Yang, Y.Y. Li, Trans. Nonferrous Met. Soc. China 28 (2018) 1061-1072. DOI URL
[51]	Y.L. Zhao, W.W. Zhang, C. Yang, D.T. Zhang, Z. wang, J.Mater. Res. 33 (2018) 898-911.
[52]	C.M. Adam, L.M. Hogan, Acta Metall. 23 (3) (1975) 345-354. DOI URL
[53]	M.A. Mohtadi-Bonab, M. Eskandari, J.A. Szpunar, Mater. Sci. Eng. A 620 (2015) 97-106. DOI URL
[54]	M. Kamaya, Mater. Charact. 60 (2009) 125-132. DOI URL
[55]	Z.Y. Ding, Q.D. Hu, W.Q. Lu, X. Ge, S. Cao, S.Y. Sun, T.X. Yang, M.X. Xia, J.G. Li, Mater. Charact. 136 (2018) 157-164. DOI URL
[56]	C.M. Allen, K.A.Q. O’Reilly, P.V. Evans, B. Cantor, Acta Mater. 47 (1999) 4387-4403. DOI URL
[57]	A. Khaliq, M.A. Rhamdhani, G.A. Brooks, J. Grandfield, Metall. Mater. Trans. B 45 (2014) 784-794. DOI URL
[58]	Y.P. Pang, Q. Li, Int. J. Hydrogen Energ. 41 (2016) 18072-18087. DOI URL
[59]	Y.P. Pang, D.K. Sun, Q.F. Gu, K.C. Chou, X.L. Wang, Q. Li, Cryst. Growth Des. 16 (2016) 2404-2415. DOI URL
[60]	Q. Luo, J.D. Li, B. Li, B. Liu, H.Y. Shao, Q. Li, J. Magnes. Alloys 7 (2019) 58-71.
[61]	Q. Luo, Y.L. Guo, B. Liu, Y.J. Feng, J.Y. Zhang, Q. Li, K.C. Chou, J. Mater. Sci, Technol. 44 (2020) 171-190.
[62]	D.R. Hamilton, R.G. Seidensticker, J. Appl. Phys. 31 (7) (1960) 1165-1168. DOI URL
[63]	M.A. Easton, D.H. StJohn, Acta Mater. 49 (2001) 1867-1878. DOI URL
[64]	A. Lui, P.S. Grant, I.C. Stone, K.A.Q.O.’ Reilly, Metall. Mater. Trans. A 50 (2019) 5242-5252. DOI URL
[65]	X.F. Gu, T. Furuhara, W.Z. Zhang, J. Appl. Cryst. 49 (2016) 1099-1106. DOI URL