Effects of Passes on Microstructure Evolution and Mechanical Properties of Mg–Gd–Y–Zn–Zr Alloy During Multidirectional Forging

The Mg-12Gd-1Er-1Zn-0.9Zr (wt%) alloy with ultra-high strength and ductility was developed via hot extrusion combined with pre-deformation and two-stage aging treatment. The age-hardening behavior and microstructure evolution were investigated. Pre-deformation introduced a large number of dislocations, resulting in strain hardening and higher precipitation strengthening in the subsequent two-stage aging. As a result, the alloy showed a superior strength-ductility balance with a yield strength of 506 MPa, an ultimate tensile strength of 549 MPa and an elongation of 8.2% at room temperature. The finer and denser β′ precipitates significantly enhanced the strength, and the bimodal structure, small β-Mg 5 RE phase as well as dense γ′ precipitates ensured the good ductility of the alloy. It is suggested that the combination of pre-deformation and two-stage aging treatment is an effective method to further improve the mechanical properties of wrought Mg alloys.

Section: Resultsmentioning

confidence: 70%

Obtaining Ultra-High Strength and Ductility in a Mg–Gd–Er–Zn–Zr Alloy via Extrusion, Pre-deformation and Two-Stage Aging

Jia

et al. 2020

“…11b precipitates. On the one hand, the interactions between dislocation and boundaries would be reduced for an alloy with a larger grain size [57]. On the other hand, the strain hardening after yielding caused by dynamic precipitates is affected by dislocation strain field interactions, which can be described as [55]:…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Microstructure, Tensile Properties and Work Hardening Behavior of an Extruded Mg–Zn–Ca–Mn Magnesium Alloy

Nie

Zhu

Munroe

et al. 2020

A new Mg-2.2 wt% Zn alloy containing 1.8 wt% Ca and 0.5 wt% Mn has been developed and subjected to extrusion under different extrusion parameters. The finest (~ 0.48 μm) recrystallized grain structures, containing both nano-sized MgZn 2 precipitates and α-Mn nanoparticles, were obtained in the alloy extruded at 270 °C/0.01 mm s −1 . In this alloy, the deformed coarse-grain region possessed a much stronger texture intensity (~ 32.49 mud) relative to the recrystallized fine-grain region (~ 13.99 mud). A positive work hardening rate in the third stage of work hardening curve was also evident in the alloy extruded at 270 °C, which was related to the sharp basal texture and which provided insufficient active slip systems. The high work hardening rate in the fourth stage contributed to the high ductility extruded at 270 °C/1 mm s −1 . This alloy exhibited a weak texture, and the examination of fracture surface revealed highly dimpled surfaces. The optimum tensile strength was achieved in the alloy extruded at 270 °C/0.01 mm s −1 , and the yield strength, ultimate tensile strength and elongation to failure were ~ 364.1 MPa, ~ 394.5 MPa and ~ 7.2%, respectively. Fine grain strengthening from the recrystallized fine-grain region played the greatest role in the strength increment of this alloy compared with Orowan strengthening and dislocation strengthening in the deformed coarse-grain regions.

“…In the past, extensive works have been published on Mg-Gd and Mg-Nd system alloys due to their enhanced mechanical properties [4,5]. High-performance cast Mg-Gd alloys often contain a high concentration of element Gd (10-20 wt%) to efficiently improve the age-hardening response [6]. However, the high total RE content significantly increases the cost and limits the practical applications of Mg-Gd alloys.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Characteristics and Mechanical Properties of Cast Mg–3Nd–3Gd–xZn–0.5Zr Alloys

Xie

Zhang

et al. 2021

The microstructure, aging behavior and mechanical properties of cast Mg-3Nd-3Gd-xZn-0.5Zr (x = 0, 0.5, 0.8, 1 wt%) alloys are investigated in this work. Zn-Zr particles with different morphologies form during solution treatment due to the additions of Zn. As the Zn content increases, the number density of Zn-Zr particles also increases. Microstructural comparisons of peak-aged studied alloys indicate that varying Zn additions could profoundly influence the competitive precipitation behavior. In the peak-aged Zn-free alloy, β′′ phases are the key strengthening precipitates. When 0.5 wt% Zn is added, besides β′′ precipitates, additional fine β 1 precipitates form. With the addition of 0.8 wt% Zn, the peak-aged 0.8Zn alloy is characterized by predominantly prismatic β 1 and scanty basal precipitate distributions. The enhanced precipitation of β 1 should be primarily attributable to the presence of increased Zn-Zr dispersoids. When Zn content further increases to 1 wt%, the precipitation of basal precipitates is markedly enhanced. Basal precipitates and β 1 phases are the key strengthening precipitates in the peak-aged 1Zn alloy. Tensile tests reveal that the relatively best tensile properties are achieved in the peak-aged alloy with 0.5 wt% Zn addition, whose yield strength, ultimate tensile strength and elongation are 179 MPa, 301 MPa and 5.3%, respectively.