Ternary Al–Ni–Er System | Encyclopedia MDPI

Ternary Al–Ni–Er System: History

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Subjects: Materials Science, Characterization & Testing

Contributor:

Qian Song

Chenbo Li

Zixuan Deng

Ligang Zhang

Libin Liu

Al–Ni–Er is an essential system in heat-resistant Al alloys. The aluminum-rich corner of this system, which has the most practical application significance. The phase equilibria of the Al–Ni–Er system are investigated via experiments and thermodynamic modeling. The isothermal sections of the Al-rich corner of this ternary system at 600 and 700 °C were determined through equilibrated alloys combined with scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffractometry (XRD).

Al–Ni–Er system
equilibrated alloys
isothermal sections

1. Introduction

Aluminum alloys have a history of nearly a century, but they have developed rapidly. The addition of nickel in aluminum alloys offers higher tensile strength and hardness, greatly improves corrosion resistance [1], and has high specific strength that could effectively reduce the weight of products, lower fuel consumption, and save energy in industrial production [2,3]. It can also promote a reduction in carbon emissions and help in achieving carbon neutrality [4]. The amorphous aluminum alloy has better properties than those of ordinary aluminum alloys. The glass-forming ability (GFA) of Al alloys could be promoted with the addition of rare earth metals (REs) [5,6,7]. Through a comprehensive consideration of cost and performance, we chose the Al–Ni–Er system as our research object.

Phase diagrams and thermodynamics are powerful tools applied to material design [8,9,10,11]. CALPHAD is a more efficient method than experimental research because an experiment cannot cover all points in a 3D phase diagram model, and CALPHAD can obtain comprehensive information that can guide the experiment. Al–Ni–Er is an essential system in heat-resistant Al alloys. Studying its thermodynamics can not only guide the design of Al–Ni–Er alloys, but also supplement the database of Al-based alloys.

2. Binary Al–Ni System

In 1993, Okamoto [12] revised Nash’s [13] evaluation of the binary Al–Ni system, and rereported the experimental phase diagram of the system. The binary Al–Ni phase diagram evaluated by Okamoto is the generally accepted version. In the binary Al–Ni system, there are two terminal solid solutions with an FCC structure, the three intermetallic compounds of NiAl₃, Ni₂Al₃, and Ni₅Al₃, and an NiAl phase with a B2-ordered structure and an Ni₃Al phase with an L1₂-ordered structure. AlNi, Al₃Ni₂, and AlNi₃ had a certain range of solid solubility at 600 and 700 °C [14].

Since Gwyer [15] initiated his work, many experiments have been carried out to determine the phase equilibrium and thermodynamic quantities of the Al–Ni system. Kaufman, and Nesor and Ansara et al. [16] produced a thermodynamic model of the whole system through phase diagram calculation. Then, Du [17], Ansara [16], Huang [18], Dupin [19], Lu [20], and Chen [21] used different models to optimize this system. The calculated phase diagram and thermodynamic description of Al–Ni were also constantly updated. The final thermodynamic model and parameters of Al–Ni binary system can be found in the thermodynamic simulation of the ternary Al–Cr–Ni system by Dupin et al. [19]. Figure 1 is the Al–Ni binary phase diagram drawn according to the thermodynamic parameters in the literature.

Figure 1. Al–Ni phase diagram [14,22].

3. Binary Er–Ni System

The phase equilibrium relation of the binary Er–Ni system was first studied by Buschow [23] in 1968. In total, 11 intermetallic compounds were identified: ErNi₃, Er₂Ni₇, ErNi₄, Er₄Ni₁₇, Er₅Ni₂₂, ErNi₅, Er₂Ni₁₇, Er₃Ni, Er₅Ni₃, ErNi, and ErNi₂. In 1974, Moreau et al. [24] studied the Er₃Ni₂ compound and found that Er₅Ni₃ should be replaced by Er₃Ni₂. Subsequently, in 1999, Du et al. [25] used the CALPHAD method to assess thermodynamic parameters and established a comprehensive thermodynamic database of this binary system. The phase diagram of the Er–Ni binary system calculated by Du et al. is shown in Figure 2 [25].

Figure 2. Er–Ni phase diagram assessed by Du et al. [25].

4. Binary Al–Er System

In 1965, The binary Al–Er system was first studied by Buschow and Vucht [26]. They discovered AlEr₂, Al₂Er₃, AlEr, Al₂Er, and Al₃Er. Their study indicated that the solid solubility of Al in Er was close to 8 at. % at 860 °C, which seemed unusually high. In 1988, Gschneidner and Calderwood [27] restudied this system. Considering the 23% size difference between Er and Al, the actual solid solubility had to be less than 1 at. %. The previous observation might have been due to an impurity effect or nonequilibrium conditions. However, in their results, the curvature change in the liquidus curve did not conform to convention in the 50 to 80 at. % Er composition range. In 2002, Cacciamani et al. [28] conducted thermodynamic modeling and optimization for the Al–Er system, and their Al–Er phase diagram is shown in Figure 3. In 2022, L Xu et al., thermodynamically assessed this system [29].

Figure 3. Calculated Al–Er phase diagram by Cacciamani et al. [28].

5. Ternary Al–Ni–Er System

There is relatively little information about the ternary Al–Ni–Er system. In 1982, Zarechnyuk et al. [30] first reported that the Er content in this system was 0–33 at. %. At the isothermal cross section at 800 °C, nine intermediate compounds were determined: τ4–Al₄NiEr, τ5–Al_3–xNi_2+xEr, τ6–Al₂NiEr, τ7–AlNi₈Er₃, τ8–Al₂Ni₆Er₃, τ9–AlNi₂Er₂, τ10–AlNiEr, Al₇Ni₃Er₂, and Al₁₆Ni₃Er. Combined with the later findings regarding the τ2–Al₉Ni₃Er phase, the Al₂Ni₃Er phase was reported by Gladyshevskii [31], and Sorgic et al. [32]. Riccardo et al. [33] drew a relatively complete isothermal section phase diagram of the ternary Al–Ni–Er system at 800 °C, as shown in Figure 4.

Figure 4. Al–Ni–Er phase diagram assessed by Riccardo et al. [33].

On the basis of the above research, Zhao et al. [34] used the equilibrium alloy method to determine most of the phase diagram of the ternary Al–Ni–Er system at 600 °C with Er content from 0 to 67 at. %. Three new ternary mesophase, namely, AlNiEr₄, AlNi₆Er₁₃ and AlNi₂Er were named τ11, τ12, and τ13. Because the pure phase was not obtained in the experiment, the structures of these ternary compounds were not discussed. The above work also revised ErNi₅ τ5. Al₂Er, ErNi₂, and τ10. The isothermal section of the ternary Al–Ni–Er system at 600 °C was drawn as shown in Figure 5.

Figure 5. Al–Ni–Er phase diagram assessed by Zhao et al. [34].

Similarly, Zhao et al. measured the isothermal section of the Al–Ni–Er system at 700 °C and 6 phase zones at the Al-rich corner: Al₂Er + Al₃Er + τ4, Al + τ1 + τ2, Al + τ2 + Al₃Ni, Al₃Ni₂ + τ2 + Al₃Ni, Al + τ1 + Al₃Er, and τ1 + Al₃Er + τ4. At the Al-rich corner (60–100% Al) of the experimental phase diagram of the ternary Al–Ni–Er alloy, at the margin, there were four ternary intermetallic compounds, namely, τ1, τ2, τ3, τ4, and four binary compounds, Al₃Ni₂, Al₃Ni, Al₂Er and Al₃Er.

According to the literature research, Al₂Er should show a certain solid solubility to Ni in a parallel direction to Er. The ideal stoichiometric composition, solid-phase crystal structure, and lattice parameters of the above compounds could be obtained by investigating the existing literature data, as shown in Table 1.

Table 1. Crystallographic data of all phases in the Al–Ni–Er system.

System	Phase	Prototype	Pearson Symbol	Lattice Parameters (nm)			Refs.
System	Phase	Prototype	Pearson Symbol	a	b	c	Refs.
Al	Fcc_A1, (Al)	Cu	cF4	0.40496			[35]
Ni	Fcc_A1, (Ni)	Cu	cF4	0.3524			[35]
Er	Hcp_A3, (Er)	Mg	hP2	0.359		0.555	[35]
Al–Ni	Al3Ni	Al3Ni	oP16	0.6613	0.7367	0.4811	[36]
	Al3Ni2	Al3Ni2	hP5	0.4028		0.4811	[37]
	AlNi	CsCl	cP2	0.28872			[35]
	Al3Ni5	Pt5Ga3	oC16	0.753	0.661	0.376	[35]
	AlNi3	Cu3Au	cP4	0.35792			[35]
	Al4Ni3	Ga4Ni3	cI112	1.144			[22]
Ni–Er	Er2Ni17	Th2Ni17	hP38	0.8287		0.8017	[22]
	Er5Ni22		hP108	0.4862		7.177	[22]
	Er4Ni17		hP126	0.4869		8.407	[22]
	ErNi4	PuNi4	mS30	0.4855	0.8444	1.0231	[22]
	Er2Ni7	Gd2Co7	hR54	0.4909		3.6067	[38]
	ErNi3	PuNi3	hR36	0.4941		2.4252	[30]
	ErNi2	MgCu2	cF24	0.71175			[31]
	Er3Ni2	Er3Ni2	hR45	0.8472		1.5680	[39]
	ErNi	FeB	oP8	0.6977	0.4110	0.5443	[39]
	Er3Ni	Fe3C	oP16	0.6804	0.9432	0.6245	[40]
Al–Er	Al3Er	AuCu3	cP4	0.4235			[26]
	Al2Er3	Al2Zr3	tP20	0.81323		0.75039	[41]
	AlEr2	Co2Si	oP12	0.6516	0.5015	0.9279	[42]
	AlEr	AlDy	oP16	0.55791	1.1277	0.5574	[43]
Al–Ni–Er
τ1	Al19Ni5Er3	Al119Ni5Gd3	oS108	4.0565	15.8906	26.9752	[24]
τ2	Al9Ni3Er	Al9Ni3Er	hR78	7.2716		27.346	[44]
τ3	Al14Ni7Er3	Al14Ni7Gd3	hP72	17.8776		4.03212	[25]
τ4	Al4NiEr	YNiAl4	oS24	4.044	15.08	6.631	[22]
τ5	Al3–xNi2+xEr	Al3Ni2Y	hP18	9.01		4.049	[22]
τ6	Al2NiEr	MgCuAl2	oS16	4.064	10.06	6.898	[22]
τ7	AlNi8Er3	Ce3Co8Si	hP24	5.002		15.99	[22]
τ8	Al2Ni6Er3	Ce3Ni6Si2	cI44	8.88			[22]
τ9	AlNi2Er2	W2CoB2	oI10	5.347	8.374	4.157	[37]
τ10	AlNiEr	AlNiZr	hP9	6.970		3.8003	[45]
τ11	AlNiEr4						[34]
τ12	AlNi6Er13						[34]
τ13	AlNi2Er						[34]
τ14	Al12Ni2Er3						This work

This entry is adapted from the peer-reviewed paper 10.3390/pr11041061

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