Achieving high strength and excellent ductility in a Zn-3Cu-1Mg alloy through minor Nd addition and multi-pass ECAP

doi:10.1016/j.metadv.2026.02.022

Abstract

Abstract:

Nd element has been extensively investigated in biodegradable magnesium alloys due to its superior strengthening effect and biocompatibility. However, the role of Nd in biodegradable zinc alloys remains poorly understood. This work elucidates the impact of Nd microalloying (0.3 wt%) on Zn-3Cu-1Mg alloy processed via multi-pass equal channel angular pressing (ECAP). The as-cast alloy exhibited a composite microstructure comprising η-Zn solid solution, CuZn₅ phase, lamellar η-Zn/Mg₂Zn₁₁ eutectic, and petaloid NdZn₁₁ particles. 8 pass (8 P) and 12 pass (12 P) ECAP processing induced severe plastic deformation in the alloy, resulting in a refined grain structure through dynamic recrystallization. However, the shape and size of the petal-like NdZn₁₁ phase remain largely unchanged, despite the development of numerous cracks within them. The alloy subjected to 12 P ECAP exhibits exceptional strength-ductility synergy, with yield strength (352 MPa), ultimate tensile strength (402 MPa), and elongation (31.7%)—a mechanical profile which not only meet the performance requirements for degradable metals but also surpass those of existing RE-containing zinc alloys. The significant improvement in strength is attributed to microstructural refinement and heterogeneous deformation strengthening from the alternating arrangement of soft CuZn₅ layers and hard eutectic layers. The extensive cracking within the petal-like NdZn₁₁ phase facilitates energy absorption and dissipation during deformation, thereby delaying crack propagation and enhancing the alloy's ductility. This study elucidates the evolution mechanisms of the NdZn₁₁ phase, providing a theoretical foundation for engineering high-performance zinc alloys through rare earth element alloying.

Key words: Zn alloy, Rare earth element, Equal channel angular pressing, Microstructure, Mechanical properties

Huan Liu, Yinyuan Chen, Lifeng Ye, Xiaoyu Qin, Chao Sun, Zhangwei Yang, Yuna Wu, Jia Ju, Wenkai Wang. Achieving high strength and excellent ductility in a Zn-3Cu-1Mg alloy through minor Nd addition and multi-pass ECAP[J]. Metals Advances, 2026, 42: 23-33.

Figures/Tables 14

Fig. 1. (a) XRD pattern and (b) SEM image of the as-cast Zn-3Cu-1Mg-0.3Nd alloy; accompanied by EDS elemental distribution analysis (c-f) delineating phase constituents.

Table 1. EDS results of the locations shown in Fig. 2(b).

Alloy	Point	Atomic ratio (at.%)				Phases
Alloy	Point	Zn	Cu	Mg	Nd	Phases
Zn-3Cu-1Mg-0.3Nd	A	95.75	4.03	0.22	0.00	η-Zn
	B	84.8	15.2	0.00	0.00	CuZn₅
	C	83.42	2.42	14.16	0.00	η-Zn+Mg₂Zn₁₁
	D	89.11	3.33	0.31	7.24	NdZn₁₁

Fig. 2. TEM images of the (a) eutectic structure and (b) its corresponding SAED patterns. TEM images of the (c) NdZn11 phase and (d) its corresponding SAED patterns of as-cast Zn-3Cu-1Mg-0.3Nd alloy.

Fig. 3. SEM analysis of Zn-3Cu-1Mg-0.3Nd alloy after multi-pass ECAP (200 °C), comparing 8 P (a, c, e) and 12 P (b, d, f). Magnified views (e, f) of NdZn11 phase illustrate crack initiation under progressive deformation.

Table 2. EDS results of the locations shown in Fig. 2(c) and (d).

Alloy	Point	Atomic ratio (at.%)				Phases
Alloy	Point	Zn	Cu	Mg	Nd	Phases
8P-200 °C	A	88.97	2.98	8.05	0.00	η-Zn+Mg₂Zn₁₁
	B	83.75	16.15	0.08	0.00	CuZn₅
	C	88.92	2.48	0.33	8.27	NdZn₁₁
12P-200 °C	D	89.45	7.67	2.88	0.00	η-Zn+Mg₂Zn₁₁
	E	84.81	14.61	0.58	0.00	CuZn₅
	F	91.96	3.37	1.02	3.64	NdZn₁₁

Fig. 4. EBSD-BC maps of Zn-3Cu-1Mg-0.3Nd alloy: (a) 8 P; (b) 12 P.

Fig. 5. (a) Typical tensile engineering curves of Zn-3Cu-1Mg-0.3Nd alloy at room temperature by ECAP processing and (b) comparison of UTS and EL for the Zn-RE alloys [31], [32], [33], [59], [60], [61], [62], [63], [64], [65] (Red line represents clinical requirements for implant materials).

Fig. 6. (a, c) IPF maps and (b, d) grain size distributions of Zn-3Cu-1Mg-0.3Nd alloy processed via ECAP: (a, b) 8 P and (c, d) 12 P.

Fig. 7. Integrated analysis of recrystallization behavior, strain heterogeneity, and crystallographic texture in Zn-3Cu-1Mg-0.3Nd alloy processed by ECAP: 8 P (a, d, g) and 12 P (b, e, h). (c) Area fractions of recrystallized, substructured, and deformed zones. (f) Frequency distribution of KAM values.

Fig. 8. Grain boundary misorientation maps of Zn-3Cu-1Mg-0.3Nd alloy processed by ECAP: (a, b) 8 P; (c, d) 12 P.

Fig. 9. Schmid factor of Zn-3Cu-1Mg-0.3Nd alloy subjected to ECAP: (a) 8 P and (b) 12 P.

Table 3. Schmid factor evolution in ECAP-processed Zn-3Cu-1Mg-0.3Nd alloy: deformation-induced slip system transitions across 8 P and 12 P.

Slip system	Slip type	8P-200 ℃	12P-200 ℃
{0001} <11-20>	basal slip <a>	0.30	0.37
{10-10} <11-20>	prismatic <a>	0.16	0.21
{1-101} <11-20>	pyramidal <a>	0.29	0.35
{10-11} <−1-123>	primary <c+a>	0.27	0.35
{11-22} <−1-123>	secondary <c+a>	0.40	0.35

Fig. 10. TEM images of matrix grains and phases of Zn-3Cu-1Mg-0.3Nd alloy after 12 P of ECAP: (a, b) matrix grains; (c) analyzed phases; (d) eutectic regions.

Fig. 11. SEM images of fracture-proximal regions in ECAP-deformed Zn-3Cu-1Mg-0.3Nd alloy: (a, b) 8 P and (c, d) 12 P, with magnified views illustrating NdZn11 phase-mediated crack deflection and localized energy absorption.

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