Effects of Mechanical Milling and Sintering Temperature on the Densification, Microstructure and Tensile Properties of the Fe-Mn-Si Powder Compacts

doi:10.1016/j.jmst.2016.08.024

Abstract

Abstract:

This work reported on the effects of mechanical milling and sintering temperature on the densification, microstructure and mechanical properties of the Fe-28Mn-3Si (wt%) alloy. Elemental Fe, Mn and Si powders were used as the starting materials, and two batches of powder mixture were prepared: one was blended elemental (BE) powder mixture; the other was mechanically milled (MM) powder mixture milled for 5 h using planetary ball milling. Both powder mixtures were pressed under a uniaxial pressure of 400 MPa, and subsequently sintered in a high vacuum furnace for 3 h at 1000, 1100, 1200 and 1300 °C. It was found that Mn depletion region (MDR) was formed on the surface of all the sintered samples. The sintered BE compacts had a low density (<68.2%) at all temperatures, while the density of the sintered MM compacts increased drastically from ~65% at 1000 °C to ~91% at 1300 °C. All the sintered MM compacts were composed of a predominant γ-austenite and minor ε-martensite. In comparison, additional (Fe, Mn)₃Si phase was observed in the BE alloys sintered at 1000 °C, and a single α-Fe phase was identified in the BE compact sintered at 1300 °C. The tensile properties of the sintered MM compacts increased significantly with the temperature and were significantly higher than those of their BE counterparts.

Key words: Fe-Mn-Si alloys, Vacuum sintering, Density, Microstructure, Tensile properties

Xu Zhigang,A. Hodgson Michael,Cao Peng. Effects of Mechanical Milling and Sintering Temperature on the Densification, Microstructure and Tensile Properties of the Fe-Mn-Si Powder Compacts[J]. J. Mater. Sci. Technol., 2016, 32(11): 1161-1170.

Figures/Tables 19

Fig. 1. Morphologies of the starting elemental powders: (a) Fe powder; (b) Mn powder; (c) Si powder.

Table 1. Particle size of the starting powder

Powder	Particle size (µm) --------------			Impurities (wt%) ---------------
Powder	d₁₀	d₅₀	d₉₀	O	C	N
Fe	19.96	38.62	68.13	0.18	0.07	0.02
Mn	14.91	38.7	78.2	0.11	0.07	0.07
Si	18.17	43.41	90.25	0.09	0.03	0.05

Fig. 2. Heating profile of Fe-28Mn-3Si powder mixture sintered for 3 h at different sintering temperatures.

Fig. 3. Mn concentration at the cross section of the sintered Fe-Mn-Si alloys at different temperatures for 3 h: (a) BE compacts sintered at 1200 °C; (b) BE compacts sintered at 1300 °C; (c) MM compacts sintered at 1300 °C.

Table 2. Thickness of MDR and the average chemical compositions of the sintered Fe-28Mn-3Si compacts

Powder mixture	Sintering temperature (°C)	Thickness of MDR (µm)	Chemical composition (wt%)^a -----------------------------------
Powder mixture	Sintering temperature (°C)	Thickness of MDR (µm)	Mn	Si	O	Fe
BE	1000	—^b	28.1 ± 1.25	3.08 ± 0.58	0.39 ± 0.05	Bal.
	1100	650 ± 35	27.8 ± 1.42	3.22 ± 0.5	0.37 ± 0.06	Bal.
	1200	1250 ± 56	28.2 ± 1.2	3.25 ± 0.2	0.41 ± 0.05	Bal.
	1300	—^c	5.1 ± 0.8	3.51 ± 0.3	0.42 ± 0.08	Bal.
MM	1000	—^b	27.6 ± 0.87	2.9 ± 0.39	0.49 ± 0.09	Bal.
	1100	255 ± 23	28.1 ± 1.35	3.15 ± 0.23	0.45 ± 0.07	Bal.
	1200	460 ± 31	27.89 ± 0.61	3.36 ± 0.15	0.42 ± 0.05	Bal.
	1300	550 ± 45	27.6 ± 1.1	3.16 ± 0.25	0.45 ± 0.09	Bal.

Fig. 4. Macroscopic images of Fe-Mn-Si alloys after being sintered for 3 h at different temperatures: (a) BE compacts and (b) MM compacts.

Fig. 5. Sintered density of BE and MM compacts sintered for 3 h as a function of sintering temperature, and the relative density of BE and MM green compacts at room temperature (Note: the relative density of the BE alloys sintered at 1300 °C is not given, due to significant sublimation of Mn during sintering at this temperature, as shown in Table 2.).

Fig. 6. XRD patterns of the BE green compacts (a) and 5 h MM green compacts (b).

Fig. 7. XRD patterns of the BE compacts sintered for 3 h at: (a) 1000 °C; (b) 1100 °C; (c) 1200 °C; (d) 1300 °C.

Fig. 8. XRD patterns of the MM compacts sintered for 3 h at: (a) 1000 °C; (b) 1100 °C; (c) 1200 °C; (d) 1300 °C.

Fig. 9. Microstructure of Fe-Mn-Si green compacts: (a) and (b) BE green compacts; (c) MM compacts; (d) enlarged rectangular area in (c).

Fig. 10. SEM micrographs of BE compacts sintered at (a) 1000 °C, (b) 1100 °C, (c) 1200 °C, (d) 1300 °C; (e) EDX spectrum from the square box ‘A’ in (a), and (f) EDX spectrum from the square box ‘B’ in (b).

Fig. 11. Microstructure of the MM compacts sintered at: (a) 1000 °C; (b) 1100 °C; (c) 1200 °C; (d) 1300 °C.

Fig. 12. Tensile stress-strain curves of Fe-28Mn-3Si compacts sintered at various temperatures: (a) BE compact at 1100 °C; (b) BE compact at 1300 °C; (c) MM compact at 1100 °C; (d) MM compact at 1300 °C.

Table 3. Static tensile properties of Fe-Mn-Si alloys sintered for 3 h at different sintering temperatures

Type of sintered powder mixture	Sintering temperature (°C)	Relative density (%)	Ultimate tensile strength (MPa)	Fracture strain (%)	Young's modulus (GPa)
Blended elemental (BE)	1000	63.5 ± 0.7	47.6 ± 4.5	—	—
	1100	64.9 ± 0.8	84.1 ± 4.2	1.75 ± 0.45	19.8 ± 0.63
	1200	68.2 ± 1.1	114.2 ± 9.8	2.66 ± 0.52	30.43 ± 1.74
	1300	—	154.9 ± 12.6	3.26 ± 0.63	30.28 ± 0.97
Mechanical milled (MM)	1000	64.8 ± 0.5	89.5 ± 5.2	1.08 ± 0.23	45 ± 2.61
	1100	77.3 ± 0.9	214.5 ± 12.1	5.1 ± 0.81	62.14 ± 1.82
	1200	85.3 ± 1.3	328.2 ± 27.3	8.45 ± 1.33	79.45 ± 2.69
	1300	90.6 ± 1.1	454.5 ± 30.2	11.86 ± 1.12	102.62 ± 4.31

Fig. 13. Ms temperature in the Fe-Mn-Si system[29].

Fig. 14. Diffusion coefficients of Fe, Mn and Si in γ-austenite phase as a function of temperature.

Fig. 15. Fracture surfaces of the Fe-28Mn-3Si alloys sintered from BE powder at different temperatures: (a) 1200 °C; (b) enlarged square area in (a); (c) 1300 °C; (d) enlarged square area in (c).

Fig. 16. Fracture surfaces of the as-sintered Fe-28Mn-3Si alloys sintered from MM powder at different temperatures: (a) 1100 °C; (b) 1200 °C; (c) enlarged square area in (b); (d) 1300 °C.

References

[1]	N. Stanford, D.P. Dunne, Acta Mater. 58(2010) 6752-6762.
[2]	T. Gebhardt, D. Music, D. Kossmann, M. Ekholm, I.A. Abrikosov, L. Vitos, J.M.Schneider, Acta Mater. 59(2011) 3145-3155.
[3]	A. Sato, E. Chishima, Y. Yamaji, T. Mori, Acta Metall. 32(1984) 539-547.
[4]	A. Sato, Y. Yamaji, T. Mori, Acta Metall. 34(1986) 287-294.
[5]	M. Koyama, T. Sawaguchi, K. Tsuzaki, Mater.Sci.Eng A 528 (2011) 2882-2888.
[6]	A. Sato, H. Kubo, T. Maruyama, Mater. Trans. 47(2006) 571.
[7]	L. Janke, C. Czaderski, M. Motavalli, J. Ruth, Mater. Struct. 38(2005) 578-592.
[8]	M. Alam, M. Youssef, M. Nehdi, Can. J. Civ. Eng. 34(2007) 1075-1086.
[9]	B. Liu, Y. Zheng, L. Ruan, Mater. Lett. 65(2011) 540-543.
[10]	Z. Xu, M.A. Hodgson, P. Cao, Mater.Sci.Eng A 630 (2015) 116-124.
[11]	P. Angelo, R. Subramanian, Powder Metallurgy: Science, Technology and Applications, PHI Learning Pvt. Ltd., Delhi,India, 2008, pp. 1-35.
[12]	M. Rahimian, N. Parvin, N. Ehsani, Mater. Des. 32(2011) 1031-1038.
[13]	A. Šalak, M. Selecka, R. Bureš, Powder Metall. Prog. 1(2001) 41-58.
[14]	H. Danninger, R. Pottschacher, S. Bradac, A. Šalak, J. Seyrkammer, Powder Metall.Prog. 48(2005) 23-32.
[15]	A. Šalak, M. Selecka, Manganese in Powder Metallurgy Steels, Springer Science& Business Media, Berlin,Germany, 2012.
[16]	L. Lu, M.O. Lai, Mechanical Alloying, Springer Science & Business Media, Berlin,Germany, 2013.
[17]	C. Suryanarayana, Prog. Mater. Sci. 46(2001) 1-184.
[18]	C. Suryanarayana, N. Al-Aqeeli, Prog. Mater. Sci. 58(2013) 383-502.
[19]	S. Torkan, A. Ataie, H. Abdizadeh, S. Sheibani, Powder Technol. 267(2014)145-152.
[20]	M. Zhu, L. Dai, N. Gu, B. Cao, L. Ouyang, J. AlloysCompd. 478(2009) 624-629.
[21]	K. Gheisari, S. Javadpour, J. Oh, M. Ghaffari, J. AlloysCompd. 472(2009) 416-420.
[22]	S. Garroni, S. Enzo, F. Delogu, Scr. Mater. 83(2014) 49-52.
[23]	P. Shyni, A. Perumal, J. AlloysCompd. 648(2015) 658-666.
[24]	M. Kalita, A. Perumal, A. Srinivasan, J. Magn.Magn.Mater. 320(2008) 2780-2783.
[25]	T. Liu, H. Liu, Z. Zhao, R. Ma, T. Hu, Y. Xie, Mater.Sci.Eng A 271 (1999) 8-13.
[26]	R.M. German, Powder Metallurgy and Particulate Materials Processing: The Processes, Materials, Products, Properties and Applications, Metal PowderIndustries Federation, Princeton,USA, 2005, pp. 221-260.
[27]	V. Raghavan, G.V. Raynor, V.G. Rivlin, Phase Diagrams of Ternary Iron Alloys,Indian Institute of Metals, Delhi, India, 1987, pp. 363-377.
[28]	N. Lebrun, Iron Systems, Part 4, Springer, Berlin, Germany, 2008, pp. 319-358.
[29]	S. Cotes, A. Fernandez Guillermet,M. Sade, J. AlloysCompd. 280(1998) 168-177.
[30]	Y. Liu, L. Zhang, Y. Du, D. Yu, D. Liang, Calphad 33 (2009) 614-623.
[31]	P. Franke, G. Inden, Zeitschrift fur Metallkunde 88 (1997) 795-799.
[32]	D. Liu, L. Zhang, Y. Du, S. Cui,W. Jie, Z. Jin, Int. J. Mater. Res. 104(2013) 135-148.
[33]	V. Witusiewicz, F. Sommer, E. Mittemeijer, J. PhaseEquilib.Diffus. 25(2004)346-354.
[34]	L.J. Gibson, M.F. Ashby, Cellular Solids: Structure and Properties, CambridgeUniversity Press, Cambridge, United Kingdom, 1999.