**1. Introduction**

Magnesium materials usually have very low density and high specific strength. The intended applications of lightweight magnesium products are primarily in the automotive or aerospace industries [1]. The addition of alloying elements determines the fundamental properties of the alloys. In our study, we focused on Mg–RE–Zn alloys, namely a Mg–Nd–Zn alloy.

Zn is often utilized as an alloying element in magnesium alloys, because it can improve mechanical properties of Mg alloys by solid solution strengthening [2]. However, for practical purposes in structural parts, the strength and fracture toughness of binary Mg–Zn alloys should be further improved, including at elevated temperatures [3]. It has been reported that rare earth (RE) elements can improve the tensile properties of Mg alloys both at room temperature and at elevated temperatures [4]. Even a low additional content of Nd can result in significant increases in hardness and yield strength of ternary Mg–Zn–Nd alloys after adequate thermal treatment [3]. The increase in hardness and strength is caused by the formation of plate-shaped Guinier–Preston (GP) zones and Mg3Nd phases [5]. The addition of

Zn to Mg–RE alloys decreases the required concentrations of RE additions for achieving mechanical properties similar to binary Mg–RE alloys. This is beneficial for the adoption of RE-containing Mg alloys in industrial applications (such as the automotive industry) since RE elements are relatively expensive [6]. Yang et al. studied the mechanical properties and microstructure of Mg–4.5 Zn–*x* Nd (*x* = 0, 1, and 2 wt.%) alloys, and the best mechanical properties were obtained in the alloy with smaller amounts of Nd (1 wt.% of Nd) [3]. We also considered Nie's thorough review in which he showed that increased content of Zn (>1.3 wt.%) in Mg–Nd–Zn alloys can cause detrimental effects on the possible precipitation hardening [7]. Therefore, the presented study focuses on low-alloyed magnesium alloy ZN11 (Mg–1 wt.% Zn–1 wt.% Nd).

Solid solution strengthening and precipitation hardening are very effective and important in all magnesium alloys. Additionally, grain boundary strengthening is capable of further improving mechanical properties. Severe plastic deformation techniques are very useful methods for preparing ultrafine-grained materials.

Equal-channel angular pressing (ECAP) is a severe plastic deformation (SPD) technique based on repetitive simple shear. The facility for ECAP is comparatively simple and it is easily scaled-up to produce materials with reasonably large dimensions [8]. Various magnesium alloys were successfully prepared by ECAP, and the obtained microstructures were ultrafine-grained or even nanostructured (depending on the ECAP process parameters, especially ECAP temperature, and on the processed material—the amount and type of alloying elements and previous thermo-mechanical treatments) [9–11]. Zhao et al. investigated Mg–3.0Nd–0.4Zn–0.5Zr alloy, prepared by integrated extrusion and ECAP, and an ultrafine-grained microstructure with an average grain size of ~0.5 μm was obtained [12]. Zhang et al. prepared a Mg–2.0Nd–0.2 wt.% Zn alloy by friction stir processing, which resulted in grain refinement to ~2 μm [13]. Analogous grain refinement to the grain size of ~2 μm was achieved by Dvorský et al. in a similar Mg–3.0Nd–0.5Zn alloy, processed by hot extrusion only [14].

Properties of low-alloyed Mg–Nd–Zn alloys processed by the SPD method have not yet been properly studied.

In this contribution, the low-alloyed magnesium alloy ZN11—prepared by extrusion and ECAP—was investigated with a focus on microstructure, texture, secondary phases, and mechanical properties.
