Phase equilibria and crystal structure of ternary compounds in Al-rich corner of Al-Er-Y system at 673 and 873K

doi:10.1016/j.jmst.2020.04.047

Abstract

Abstract:

Phase equilibria in the Al-rich corner of the Al-Er-Y ternary system from 65 at.% to 100 at.% Al at 673 and 873 K were investigated, and the two isothermal sections were established by X-ray diffraction (XRD), scanning electron microscope (SEM) and electron probe micro analysis (EPMA). Three ternary-phase regions are observed and the phase relations are similar at both isothermal sections. There are two ternary compounds, and a complete crystal structures and composition ranges of the two ternary compounds are determined as τ₁ (Al_75-76Er_15-22Y_2-10, R-3m) and τ₂ (Al_75-76Er_11-17Y_7-14, P6₃/mmc) via XRD, focused ion beam coupled with transmission electron microscope (FIB-TEM) and EPMA. Meanwhile, the solubilities of the third element in the binary compounds at both temperatures are measured. The solubility of Er in β-Al₃Y phase reaches to 6.6 at.% and that of Y in Al₃Er phase reaches to 1.5 at.% after annealing at 873 K. The temperature effect is not obvious for the phase equilibria at 673 and 873 K, but it increases the solubility of Er in β-Al₃Y, while it is not obvious for both the solubility of Y in Al₃Er and that of Er and Y in (Al). The phase equilibria of the Al-Er-Y ternary system determined by the present work have provided new phase diagram data for a future thermodynamic assessment of this system.

Key words: Aluminium alloy, Phase equilibria, Al-Er-Y, XRD, EPMA, TEM

Xiaoxu Liu, Yong Du, Shuhong Liu, Kaiming Cheng, Zhihong Zhang. Phase equilibria and crystal structure of ternary compounds in Al-rich corner of Al-Er-Y system at 673 and 873K[J]. J. Mater. Sci. Technol., 2021, 60: 128-138.

Figures/Tables 15

References 26

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Compound	Space group	Prototype	Lattice parameters (nm)			Comment	Refs.
Compound	Space group	Prototype	a	b	c	Comment	Refs.
α-Al₃Y	P6₃/mmc	Ni₃Sn	0.6289(11)	—	0.4584(3)	—	[15]
β-Al₃Y	R-3m	BaPb₃	0.6188	—	2.1094	—	[15]
Al₂Y	Fd-3m	Cu₂Mg	0.7855(2)	—	—	—	[15]
AlY	Cmcm	CrB	0.3884(2)	1.152(0)	0.4385(2)	—	[15]
Al₂Y₃	P4₂/mnm	Al₂Zr₃	0.8232(4)	—	0.7632(8)	—	[15]
AlY₂	Pnma	Co₂Si	0.6636(2)	0.5086(2)	0.9471(2)	—	[15]
Al₃Er	Fm-3m	AuCu₃	0.4214	—	—	—	[14]
Al₂Er	Fd-3m	Cu₂Mg	0.7793(1)	—	—	—	[14]
AlEr	Pmma	AlEr	0.5801	1.127	0.5570	—	[14]
Al₂Er₃	P4₂/mnm	Al₂Zr₃	0.8123	—	0.7484	—	[14]
AlEr₂	Pnma	Co₂Si	0.6516	0.5015	0.9279	—	[14]
Al₃Er_1-_xY_x (τ₁)	—	HoAl₃	0.6043～0.6048	—	3.578	0.05≤x≤0.35	[20]
			0.6042	—	3.574	x = 0.17	[19]
			0.6034	—	3.574	x = 0.09	[19]
			0.6030	—	3.572	x = 0.05, sample also contains 20 wt.% AuCu₃-type Al₃Er	[19]
Al₃Er_xY_1-x (τ₂)	—	Ni₃Ti	0.6077～0.6086	—	0.9512～0.9530	0.45≤x≤0.6	[20]
			—	—	—	x = 0.50, sample also contains 95 wt.% BaPb₃-type Al₃Y	[19]
			0.6150	—	0.9519	x = 0.67, sample also contains 30 wt.% HoAl₃-type τ₁	[19]

Compound	Space group	Prototype	Lattice parameters (nm)			Comment	Refs.
Compound	Space group	Prototype	a	b	c	Comment	Refs.
α-Al₃Y	P6₃/mmc	Ni₃Sn	0.6289(11)	—	0.4584(3)	—	[15]
β-Al₃Y	R-3m	BaPb₃	0.6188	—	2.1094	—	[15]
Al₂Y	Fd-3m	Cu₂Mg	0.7855(2)	—	—	—	[15]
AlY	Cmcm	CrB	0.3884(2)	1.152(0)	0.4385(2)	—	[15]
Al₂Y₃	P4₂/mnm	Al₂Zr₃	0.8232(4)	—	0.7632(8)	—	[15]
AlY₂	Pnma	Co₂Si	0.6636(2)	0.5086(2)	0.9471(2)	—	[15]
Al₃Er	Fm-3m	AuCu₃	0.4214	—	—	—	[14]
Al₂Er	Fd-3m	Cu₂Mg	0.7793(1)	—	—	—	[14]
AlEr	Pmma	AlEr	0.5801	1.127	0.5570	—	[14]
Al₂Er₃	P4₂/mnm	Al₂Zr₃	0.8123	—	0.7484	—	[14]
AlEr₂	Pnma	Co₂Si	0.6516	0.5015	0.9279	—	[14]
Al₃Er_1-_xY_x (τ₁)	—	HoAl₃	0.6043～0.6048	—	3.578	0.05≤x≤0.35	[20]
			0.6042	—	3.574	x = 0.17	[19]
			0.6034	—	3.574	x = 0.09	[19]
			0.6030	—	3.572	x = 0.05, sample also contains 20 wt.% AuCu₃-type Al₃Er	[19]
Al₃Er_xY_1-x (τ₂)	—	Ni₃Ti	0.6077～0.6086	—	0.9512～0.9530	0.45≤x≤0.6	[20]
			—	—	—	x = 0.50, sample also contains 95 wt.% BaPb₃-type Al₃Y	[19]
			0.6150	—	0.9519	x = 0.67, sample also contains 30 wt.% HoAl₃-type τ₁	[19]

Samples	Nominal compositions (at.%)			Phases and compositions (at.%) at 873 K				Phases and compositions (at.%) at 673 K
Samples	Al	Er	Y	Phase	Al	Er	Y	Phase	Al	Er	Y
1	90	4	6	(Al)	99.8	0.1	0.1	(Al)	100.0	N.D.^a	N.D.
				τ₂	75.7	11.0	13.3	τ₂	76.0	11.4	12.6
				β-Al₃Y	76.0	6.6	17.4	β-Al₃Y	76.0	4.7	19.3
2	85	14.6	0.4	(Al)	99.9	0.1	N.D.	(Al)	99.9	0.1	N.D.
2	85	14.6	0.4	Al₃Er	76.1	23.3	0.6	Al₃Er	76.1	23.5	0.4
3	85	13.5	1.5	(Al)	99.9	0.1	N.D.	(Al)	99.8	0.2	N.D.
				τ₁	76.3	17.3	6.4	τ₁	75.9	18.8	5.3
				Al₃Er	76.5	22.0	1.5	Al₃Er	76.5	22.4	1.1
4	85	8.5	6.5	(Al)	99.8	0.1	0.1	(Al)	100	N.D.	N.D.
				τ₂	75.7	12.3	12.0	τ₂	76.0	12.6	11.4
				τ₁	75.6	15.6	8.8	τ₁	76.0	16.2	7.8
5	85	10.5	4.5	τ₁	76.2	16.6	7.2	τ₁	76.0	17.5	6.5
5	85	10.5	4.5	(Al)	99.9	0.1	N.D.	(Al)	99.9	0.1	N.D.
6	80	9.8	10.2	τ₂	76.0	11.4	12.6	τ₂	76.2	11.8	12.0
6	80	9.8	10.2	(Al)	99.7	0.2	0.1	(Al)	99.8	0.1	0.1
7	80	3	17	β-Al₃Y	75.6	3.3	21.1	β-Al₃Y	75.7	3.2	21.1
7	80	3	17	(Al)	98.9	0.2	0.9	(Al)	99.5	0.1	0.4
8	75	12	13	τ₂	75.2	12.0	12.8	τ₂	75.2	12.2	12.6
9	75	15	10	τ₂	75.2	14.9	9.9	τ₂	75.2	15.1	9.7
10	75	20	5	τ₁	75.4	19.7	4.9	τ₁	75.4	19.8	4.8
11	75	23	2	τ₁	75.4	22.5	2.1	τ₁	75.4	22.6	2.0
12	73	5.6	21.4	β-Al₃Y	75.4	5.6	19.0	β-Al₃Y	75.8	4.8	19.4
12	73	5.6	21.4	Al₂(Er,Y)	68.2	5.2	26.6	Al₂(Er,Y)	68.7	6.7	24.6
13	73	13.4	13.6	τ₂	75.3	12.3	12.4	τ₂	75.1	12.1	12.8
13	73	13.4	13.6	Al₂(Er,Y)	68.9	15.9	15.2	Al₂(Er,Y)	69.2	16.2	14.6
14	72	19	9	τ₂	75.4	16.6	8.0	τ₂	75.5	16.4	8.1
14	72	19	9	Al₂(Er,Y)	69.8	21.0	9.2	Al₂(Er,Y)	69.6	21.4	9.0
15	72	23	5	τ₁	75.4	20.6	4.0	τ₁	75.6	19.9	4.5
15	72	23	5	Al₂(Er,Y)	68.9	26.4	4.7	Al₂(Er,Y)	69.2	25.7	5.1

Samples	Nominal compositions (at.%)			Phases and compositions (at.%) at 873 K				Phases and compositions (at.%) at 673 K
Samples	Al	Er	Y	Phase	Al	Er	Y	Phase	Al	Er	Y
1	90	4	6	(Al)	99.8	0.1	0.1	(Al)	100.0	N.D.^a	N.D.
				τ₂	75.7	11.0	13.3	τ₂	76.0	11.4	12.6
				β-Al₃Y	76.0	6.6	17.4	β-Al₃Y	76.0	4.7	19.3
2	85	14.6	0.4	(Al)	99.9	0.1	N.D.	(Al)	99.9	0.1	N.D.
2	85	14.6	0.4	Al₃Er	76.1	23.3	0.6	Al₃Er	76.1	23.5	0.4
3	85	13.5	1.5	(Al)	99.9	0.1	N.D.	(Al)	99.8	0.2	N.D.
				τ₁	76.3	17.3	6.4	τ₁	75.9	18.8	5.3
				Al₃Er	76.5	22.0	1.5	Al₃Er	76.5	22.4	1.1
4	85	8.5	6.5	(Al)	99.8	0.1	0.1	(Al)	100	N.D.	N.D.
				τ₂	75.7	12.3	12.0	τ₂	76.0	12.6	11.4
				τ₁	75.6	15.6	8.8	τ₁	76.0	16.2	7.8
5	85	10.5	4.5	τ₁	76.2	16.6	7.2	τ₁	76.0	17.5	6.5
5	85	10.5	4.5	(Al)	99.9	0.1	N.D.	(Al)	99.9	0.1	N.D.
6	80	9.8	10.2	τ₂	76.0	11.4	12.6	τ₂	76.2	11.8	12.0
6	80	9.8	10.2	(Al)	99.7	0.2	0.1	(Al)	99.8	0.1	0.1
7	80	3	17	β-Al₃Y	75.6	3.3	21.1	β-Al₃Y	75.7	3.2	21.1
7	80	3	17	(Al)	98.9	0.2	0.9	(Al)	99.5	0.1	0.4
8	75	12	13	τ₂	75.2	12.0	12.8	τ₂	75.2	12.2	12.6
9	75	15	10	τ₂	75.2	14.9	9.9	τ₂	75.2	15.1	9.7
10	75	20	5	τ₁	75.4	19.7	4.9	τ₁	75.4	19.8	4.8
11	75	23	2	τ₁	75.4	22.5	2.1	τ₁	75.4	22.6	2.0
12	73	5.6	21.4	β-Al₃Y	75.4	5.6	19.0	β-Al₃Y	75.8	4.8	19.4
12	73	5.6	21.4	Al₂(Er,Y)	68.2	5.2	26.6	Al₂(Er,Y)	68.7	6.7	24.6
13	73	13.4	13.6	τ₂	75.3	12.3	12.4	τ₂	75.1	12.1	12.8
13	73	13.4	13.6	Al₂(Er,Y)	68.9	15.9	15.2	Al₂(Er,Y)	69.2	16.2	14.6
14	72	19	9	τ₂	75.4	16.6	8.0	τ₂	75.5	16.4	8.1
14	72	19	9	Al₂(Er,Y)	69.8	21.0	9.2	Al₂(Er,Y)	69.6	21.4	9.0
15	72	23	5	τ₁	75.4	20.6	4.0	τ₁	75.6	19.9	4.5
15	72	23	5	Al₂(Er,Y)	68.9	26.4	4.7	Al₂(Er,Y)	69.2	25.7	5.1

Alloys	Phase	Space group	a (?)	b (?)	c (?)	α (°)	β (°)	γ (°)	Volume (?³)	R_wp (%)	R_p (%)
#8	τ₂	P6₃/mmc	6.0885(1)	6.0885(1)	9.5231(3)	90	90	120	305.72(1)	13.60	9.86
#9	τ₂	P6₃/mmc	6.0806(2)	6.0806(2)	9.5168(3)	90	90	120	304.73(1)	13.94	9.83
#10	τ₁	R-3m	6.0480(2)	6.0480(2)	35.7930(21)	90	90	120	1133.86(6)	13.48	9.94
#11	τ₁	R-3m	6.0379(2)	6.0379(2)	35.7704(19)	90	90	120	1129.35(9)	12.83	9.69