Research on AZ80 + 0.4%Ce (wt %) Ultra-Thin-Walled Tubes of Magnesium Alloys: The Forming Process, Microstructure Evolution and Mechanical Properties

Abstract

Ultra-thin-walled tubes of magnesium alloys have received more and more attention in producing precision components for medical devices. Therefore, thin-walled tubes with high quality are desperately needed. In this study, the process of multi-pass variable wall thickness extrusion was carried out on an AZ80 + 0.4%Ce Mg alloy with up to five passes—one-pass backward extrusion and four-pass extension—to fabricate the seamless thin-walled tube with an inside diameter of 6.0 mm and a wall thickness of 0.6 mm. The average grain size decreased from 46.3 μm to 8.9 μm at the appropriate deformation temperature of 350 °C with the punch speed of 0.1 mm/s. X-ray diffraction (XRD), optical microscope (OM), scanning electron microscopy (SEM), and the Vickers hardness (HV) tester were utilized to study the phases, microstructure, and hardness evolution. It can be observed that low deformation temperatures (240 °C and 270 °C) and low strain (1 pass extrusion and 1 pass extension) lead to twins that occupy the grains to coordinate deformation, and a slip system was activated with the accumulation of strain. The results of the Vickers hardness test showed that twinning, precipitation of second phases, twinning dynamic recrystallization (TDRX), and work hardening were combined to change the hardness of tubes at 240 °C and 270 °C. The hardness reached 93 HV after the third pass extension without annealing at 350 °C.

Effect of Pre‐Extrusion on the Microstructure and Properties of Forged Mg−Al−Zn−Ce Alloy

“…This provided more nucleation particles for dynamic recrystallization (DRX), which was helpful to grain refinement, and also improved the room‐temperature formability of AZ80 magnesium alloy. Yan et al [ 11 ] studied the multipass variable wall thickness extrusion process of AZ80 + 0.4%Ce magnesium alloy. The results showed that the hot extrusion deformation significantly refined the grain size at an appropriate temperature.…”

Study on the Strengthening Mechanism of Rare Earth Ce in Magnesium Alloys, Based on First-Principle Calculations and Electronegativity Theory

“…By preparing Mg-Gd-x, Mg-Y-x ternary, or multiple alloy systems (x = Y [10][11][12], Sm [13,14], Nd [15], Zn [16][17][18], Ag [19][20][21], etc. ), most researchers studied the structure and precipitation sequence of rare earth strengthening phases [22], explored the mechanical properties and fracture modes of samples with different heat treatments [23], and investigated the strengthening mechanism of rare earth elements in magnesium alloys [24,25].…”

“…A large number of different types of second phases were formed as consequence [24]. Taking Mg-Ce and Al-Ce binary alloys as examples, the second phases found by experimental methods included MgCe [37], Mg 2 Ce [38], Mg 3 Ce [39], Mg 12 Ce [40], Mg 17 Ce 2 [40], AlCe [41], Al 2 Ce [42], Al 3 Ce [43], Al 4 Ce [25], Al 11 Ce 3 [44], etc. Although transmission electron microscopy (TEM), electron probe micro analyzer (EPMA), X-ray diffraction (XRD), differential scanning calorimetry (DCS), energy dispersive spectroscopy (EDS), and other techniques were used to analyze the structure and properties of these phases, the information on the formation sequence and thermodynamic stability of the phases was still limited.…”

High Ductility with a Homogeneous Microstructure of a Mg–Al–Zn Alloy Prepared by Cyclic Expansion Extrusion with an Asymmetrical Extrusion Cavity

“…Magnesium (Mg) and its alloys, which have the advantages of a low density, a high specific strength, easy recyclability, etc., have broad application prospects in national defense, aerospace, automobile, and 3C communication [1][2][3][4]. However, due to their poor strength and low ductility at room temperature, the development and application of Mg alloys are still limited [5].…”