Development of High Strength and Toughness Non-Heated Al-Mg-Si Alloys for High-Pressure Die-Casting

doi:10.1007/s40195-020-01174-1

Abstract

Abstract:

Based on the 3 factors and 3 levels orthogonal experiment method, compositional effects of Mg, Si, and Ti addition on the microstructures, tensile properties, and fracture behaviors of the high-pressure die-casting Al-xMg-ySi-zTi alloys have been investigated. The analysis of variance shows that both Mg and Si apparently influence the tensile properties of the alloys, while Ti does not. The tensile mechanical properties are comprehensively influenced by the amount of eutectic phase (α-Al + Mg₂Si), the average grain size, and the content of Mg dissolved into α-Al matrix. The optimized alloy is Al-7.49 Mg-3.08Si-0.01Ti (wt%), which exhibits tensile yield strength of 219 MPa, ultimate tensile strength of 401 MPa, and elongation of 10.5%. Furthermore, contour maps, showing the relationship among compositions, microstructure characteristics, and the tensile properties are constructed, which provide guidelines for developing high strength and toughness Al-Mg-Si-Ti alloys for high-pressure die-casting.

Key words: Al-Mg-Si-Ti alloy, Microstructure, Tensile properties, High strength and toughness, Contour maps

Ling-Yang Yuan, Pan-Wen Han, Ghulam Asghar, Bao-Liang Liu, Jin-Ping Li, Bin Hu, Peng-Huai Fu, Li-Ming Peng. Development of High Strength and Toughness Non-Heated Al-Mg-Si Alloys for High-Pressure Die-Casting[J]. Acta Metallurgica Sinica (English Letters), 2021, 34(6): 845-860.

Figures/Tables 21

Fig. 1 Vertical section of Al-5.5 Mg-Si-0.6Mn-0.15Ti (wt%) equilibrium phases diagram with Si content in the range of 0.5-3.0 wt% calculated with Pandat software

Fig. 2 a Solidification process of the Al-Mg-Si alloy; and b-d solidification range (?T), content of Mg dissolved into the matrix (M) and the proportion of eutectic compounds (E) for b Al-5.5 Mg (0.5-3.0)Si, c Al-6.5 Mg-(0.5-3.76)Si, and d Al-7.5 Mg-(0.5-4.3)Si alloys

Table 1 3 factors and 3 levels orthogonal design of HPDC Al-xMg-ySi-zTi alloys

Symbol	A	B	C	D	Tensile properties
Symbol	Mg (wt%)	Si (wt%)	Ti (wt%)	e	Tensile properties
1#	1 (6.5)	1 (2.0)	1 (0.0)	1
2#	1 (6.5)	2 (2.5)	2 (0.1)	2
3#	1 (6.5)	3 (3.0)	3 (0.2)	3
4#	2 (7.0)	1 (2.0)	2 (0.1)	3
5#	2 (7.0)	2 (2.5)	3 (0.2)	1
6#	2 (7.0)	3 (3.0)	1 (0.0)	2
7#	3 (7.5)	1 (2.0)	3 (0.2)	2
8#	3 (7.5)	2 (2.5)	1 (0.0)	3
9#	3 (7.5)	3 (3.0)	2 (0.1)	1

Fig. 3 Dimension and shape of the sample castings produced by high-pressure die-casting

Fig. 4 Casting parameters showing the shot filling speed (mm/s) and filling position (mm) at different stages

Table 2 Actual chemical compositions of HPDC Al-xMg-ySi-zTi alloys (wt%)

Symbol	Mg	Si	Ti	Mn	Fe	Other	Al
1#	6.41	2.10	0.01	0.68	0.12	< 0.3	Bal.
2#	6.43	2.57	0.09	0.67	0.13	< 0.3	Bal.
3#	6.46	3.10	0.17	0.65	0.11	< 0.3	Bal.
4#	7.02	2.09	0.12	0.71	0.13	< 0.3	Bal.
5#	7.10	2.58	0.18	0.66	0.11	< 0.3	Bal.
6#	7.06	3.11	0.01	0.71	0.13	< 0.3	Bal.
7#	7.54	1.95	0.17	0.69	0.11	< 0.3	Bal.
8#	7.51	2.53	0.01	0.68	0.12	< 0.3	Bal.
9#	7.49	3.08	0.11	0.72	0.12	< 0.3	Bal.

Fig. 5 Tensile properties of HPDC Al-xMg-ySi-zTi alloys a YS, b UTS, c EL and d tensile curves of 4#, 5#, and 6# alloys

Table 3 3 factors and 3 levels orthogonal experiment results

Symbol	A	B	C	D	Results
	Mg (wt%)	Si (wt%)	Ti (wt%)	e	EL. (%)	YS (MPa)	UTS (MPa)
1#	1 (6.5)	1 (2.0)	1 (0)	1	7.5	197	354
2#	1	2 (2.5)	2 (0.1)	2	11.4	205	398
3#	1	3 (3.0)	3 (0.2)	3	13.6	203	360
4#	2 (7.0)	1	2	3	7.0	207	368
5#	2	2	3	1	9.6	212	398
6#	2	3	1	2	11.9	213	382
7#	3 (7.5)	1	3	2	6.2	215	377
8#	3	2	1	3	8.5	221	412
9#	3	3	2	1	10.5	219	401
K_1EL	32.5	20.7	27.9	27.6	T_EL. = 86.2%
K_2EL	28.5	29.5	28.9	29.5
K_3EL	25.2	36	29.4	29.1
S_EL	8.9	39.3	0.4	0.7
K_1YS	605	619	631	628		T_YS = 1892 MPa
K_2YS	632	638	631	633
K_3YS	655	635	630	631
S_YS	417.6	69.6	0.2	4.2
K_1UTS	1112	1099	1148	1153			T_UTS = 3450 MPa
K_2UTS	1148	1208	1167	1157
K_3UTS	1190	1143	1135	1140
S_UTS	1016	2004.7	172.7	52.7

Table 4 Variance analysis of orthogonal test results

	Factors	S	D	V (S/D)	F (V_i/V_e)	Significance
EL	A	8.9	2	4.45	12.7	(*)
	B	39.3	2	19.65	56.1	*
	C	0.4	2	0.2	0.57
	e	0.7	2	0.35
YS	A	417.6	2	208.8	99.4	**
	B	69.6	2	34.8	16.6	(*)
	C	0.2	2	0.1	0.05
	e	4.2	2	2.1
UTS	A	1016	2	508	19.2	*
	B	2004.7	2	1002.5	37.8	*
	C	172.7	2	86.5	3.3
	e	52.7	2	26.5

Fig. 6 Property comparison of HPDC Al-xMg-ySi-zTi alloys with some known non-heat-treated HPDC Al alloys: field A (reported alloys); field B (Al-xMg-ySi-zTi alloys in this work)

Fig. 7 Optical micrographs of a Al-7.0 Mg-2Si-0.15Ti, b Al-7.0 Mg-2.5Si-0.2Ti, and c Al-7.0 Mg-3Si-0Ti alloys; d area fraction of the eutectic phase

Fig. 8 EBSD orientation map of a Al-7.0 Mg-2Si-0.15Ti (4#), c Al-7.0 Mg-2.5Si-0.2Ti (5#) and e Al-7.0 Mg-3Si-0Ti (6#) alloys; b, d, and f grain size distributions of 4#, 5#, and 6# alloys, respectively

Table 5 Average grain sizes of HPDC Al-xMg-ySi-zTi alloys

Alloys	Size (μm)	Alloys	Size (μm)	Alloys	Size (μm)
1#	32.4 ± 5.4	4#	33.6 ± 4.2	7#	32.2 ± 3.0
2#	23.5 ± 3.2	5#	24.5 ± 2.1	8#	25.2 ± 3.5
3#	16.1 ± 1.5	6#	18.8 ± 2.3	9#	17.3 ± 1.8

Fig. 9 a and b SEM images showing microstructures of HPDC Al-xMg-ySi-zTi alloys; c and d EDS results corresponding to points A and B in b

Table 6 Average concentration of Mg in the matrix of HPDC Al-xMg-ySi-zTi alloys measured by SEM-EDS

Alloys	Mg (wt%)	Alloys	Mg (wt%)	Alloys	Mg (wt%)
1#	3.24 ± 0.14	4#	3.74 ± 0.29	7#	4.12 ± 0.26
2#	2.44 ± 0.20	5#	2.91 ± 0.17	8#	3.31 ± 0.16
3#	1.40 ± 0.13	6#	2.11 ± 0.32	9#	2.47 ± 0.30

Fig. 10 TEM micrographs of Mg2Si phase: a bright-field and b annular dark-field image

Table 7 Variations of the microstructures and properties of HPDC Al-xMg-ySi-zTi alloys in comparison with 1# alloy

Alloys	∆E	∆Sm (μm)	∆M (wt%)	∆EL. (%)	∆YS (MPa)	∆UTS (MPa)
1#	0	0	0	0	0	0
2#	0.18	-8.9	-0.80	3.9	8	42
3#	0.52	-16.3	-1.84	6.1	6	6
4#	0.04	1.2	0.50	-0.5	10	12
5#	0.23	-7.9	-0.33	2.1	15	42
6#	0.49	-13.6	-1.13	4.4	16	28
7#	0.03	-0.2	0.88	-1.3	18	23
8#	0.30	-7.2	0.07	1	22	55
9#	0.57	-15.1	-0.77	3	24	45

Table 8 F values for ?E, ?Sm, and ?M on the Eqs. (7-9)

Properties/F	∆E	∆Sm	∆M	∆M²	∆E∆Sm∆M
∆EL	2.71	4.12	20.32	-	-
∆YS	1.22	23.00	137.23	-	-
∆UTS	15.20	4.49	-	15.84	52.98

Fig. 11 SEM images showing microstructures near the fracture surface of the HPDC Al-xMg-ySi-zTi alloys specimens: a near the fracture surface; b Fe-cracks; c E-M-cracks; d E-cracks

Fig. 12 Ratio of cracks (including Fe-cracks, E-M-cracks, and E-cracks) near the fracture of the HPDC Al-xMg-ySi-zTi alloys

Fig. 13 Contour maps of EL., YS, UTS versus the contents of Mg, Si, and the microstructure: a Mg and Si-EL.; b average grain size (Sm) and Mg content in the matrix (M)-EL.; c Mg and Si-YS; d average grain size (Sm) and Mg content in the matrix (M)-YS; e Mg and Si-UTS; f average grain size (Sm), Mg content in the matrix (M) and eutectic phase content (E)-UTS

References 30

[1]	A.I. Taub, A.A. Luo, Advanced lightweight materials and manufacturing processes for automotive applications. MRS Bull. 40, 1045 (2015) DOI URL
[2]	G.S. Cole, A.M. Sherman, Light weight materials for automotive applications. Mater. Charact. 35, 3 (1995) DOI URL
[3]	A. Morita, Aluminum alloys for automobile applications, Proceedings of the 6th International Conference on Aluminum Alloys (Proc. 6th ICAA) 1, 25 (1998)
[4]	W.S. Miller, L. Zhuang, J. Bottema, A.J. Wittebrood, P.D. Smet, A. Haszler, A. Vieregge, Recent development in aluminium alloys for the automotive industry. Mater. Sci. Eng. A 280, 37 (2000)
[5]	J.T. Staley, D.J. Lege, Advances in aluminium alloy products for structural applications in transportation. Le J. de Phys. IV. 3, 179 (1993)
[6]	S. Ji, Light-Weighted Materials for Automotive Industry. BCAST Internal Report (Brunel University, UK, 2011).
[7]	G. Davies, Materials for Automobile Bodies, 2nd edn. (Butterworth-Heinemann, Oxford, 2012).
[8]	J.G. Kaufman, E. Rooy, Aluminum Alloy Castings: Properties, Processes,Applications, 1st edn. (ASM International, US, 2004).
[9]	X. Dong, H. Yang, X. Zhu, S. Ji, High strength and ductility aluminium alloy processed by high pressure die casting. J. Alloy Compd. 773, 86 (2019) DOI URL
[10]	S. Ji, F. Yan, Z. Fan, Development of a high strength Al-Mg2Si-Mg-Zn based alloy for high pressure die casting. Mater. Sci. Eng. A 626, 165 (2015)
[11]	F. Yan, W. Yang, S. Ji, Z. Fan, Effect of solutionising and ageing on the microstructure and mechanical properties of a high strength die-cast Al-Mg-Zn-Si alloy. Mater. Chem. Phys. 167, 88 (2015) DOI URL
[12]	V.S. Zolotorevsky, N.A. Belov, M.V. Glazoff, Casting Aluminum Alloys, 1st edn. (Elsevier, Oxford, 2007).
[13]	F. Bonollo, N. Gramegna, G. Timelli, High-pressure die-casting: Contradictions and challenges. JOM 67, 901 (2015)
[14]	F. Casarotto, A.J. Franke, R. Franke, Advanced Materials in Automotive Engineering, 1st edn. (Woodhead, Cambridge,2012).
[15]	S. Ji, H. Yang, X. Cui, Z. Fan, Macro-heterogeneities in microstructures, concentrations, defects and tensile properties of die cast Al-Mg-Si alloys. Mater. Sci. Technol. 33, 2223 (2017) DOI URL
[16]	P. Zhang, Z. Li, B. Liu, W. Ding, L. Peng, Improved tensile properties of a new aluminum alloy for high pressure die casting. Mater. Sci. Eng. A 651, 376 (2016)
[17]	Z. Hu, L. Wan, S. Wu, H. Wu, X. Liu, Microstructure and mechanical properties of high strength die-casting Al-Mg-Si-Mn alloy. Mater. Des. 46, 451 (2013) DOI URL
[18]	S. Ji, D. Watson, Z. Fan, M. White, Development of a super ductile diecast Al-Mg-Si alloy. Mater. Sci. Eng. A 556, 824 (2012)
[19]	H. Koch, B. Lenczowski, Al/Mg/Si Cast Aluminium Containing Scandium. E. U. Patent 2005/047554, 26 May 2005
[20]	G. Trenda, A. Kraly, Aluminum alloy. US Patent 8,337,644,25 Dec 2012
[21]	H. Yang, D. Watson, Y. Wang, S. Ji, Effect of nickel on the microstructure and mechanical property of die-cast Al-Mg-Si-Mn alloy. J. Mater. Sci. 49, 8412 (2014) DOI URL
[22]	S. Ji, W. Yang, F. Gao, D. Watson, Z. Fan, Effect of iron on the microstructure and mechanical property of Al-Mg-Si-Mn and Al-Mg-Si diecast alloys. Mater. Sci. Eng. A 564, 130 (2013)
[23]	U. Hielscher, H. Sternau, H. Koch, R. Klos, New developed pressure die casting alloy with excellent mechanical properties in the as-cast condition. Giesserei 85, 62 (1998)
[24]	U. Hielscher, H. Sternau, H. Koch, A. Franke, Magsimal-59, an AlMgMnSi-type squeeze-casting alloy designed for temper F. Paper presented at the 125th annual meeting and exhibition of the Minerals, Metals and Materials Society, California, US, 4-8th February 1996
[25]	S. Otarawanna, C.M. Gourlay, H.I. Laukli, A.K. Dahle, Microstructure formation in AlSi4MgMn and AlMg5Si2Mn high-pressure die castings. Metall. Mater. Trans. A 40, 1645 (2009)
[26]	S. Ji, Y. Wang, D. Watson, Z. Fan, Microstructural evolution and solidification behavior of Al-Mg-Si alloy in high-pressure die casting. Metall. Mater. Trans. A 44, 3185 (2013)
[27]	N.A. Belov, D.G. Eskin, A.A. Aksenov, Multicomponent Phase Diagrams: Applications for Commercial Aluminum Alloys. (Elsevier, Oxford, 2005)
[28]	D.M. Stefanscu, J.R. Davis, J.D. Destefani (Eds.), ASM Metals Handbook, Casting. Vol. 15, 9th edn. (ASM International, US, 1998)
[29]	L. Yuan, L. Peng, J. Han, B. Liu, Y. Wu, J. Chen, Effect of Cu addition on microstructures and tensile properties of high-pressure die-casting Al-5.5 Mg-0.7 Mn alloy. J. Mater. Sci. Technol. 35, 1017 (2019) DOI URL
[30]	P. Zhang, Z. Li, B. Liu, W. Ding, Tensile properties and deformation behaviors of a new aluminum alloy for high pressure die casting. J. Mater. Sci. Technol. 33, 367 (2017) DOI URL