Effect of long-period stacking ordered phase on mechanical properties of Mg97Zn1Y2 extruded alloy

Recent developments in high-strength Mg-RE-based alloys: Focusing on Mg-Gd and Mg-Y systems

Recent research and developments on wrought magnesium alloys

Effect of multimodal microstructure evolution on mechanical properties of Mg–Zn–Y extruded alloy

Magnesium, the lightest structural metal, is approximately four times lighter than steel—the most widely used metal in industrial applications. Currently available Mg alloys, however, are impractically expensive for use in automotive structural components, as severe ductility problems require forming operations at elevated temperatures and an exclusion from critical safety components. With a strong impetus in research having sprung up during the last two decades, addition of rare-earth elements in small quantities emerged as a potential solution for simultaneously delivering the ductility and weight requirements for automotive applications. These improvements are arguably achieved by virtue of texture weakening and enhancement of non-basal slip. However, ways by which rare-earth elements modify texture remain very elusive, and no consensus on the driving mechanisms has been reached in the literature as of yet. We take a look back at different paradigms held for the action of rare-earth additions, and examine key facts that may reconcile controversies. We attempt to identify critical gaps and suggest venues to overcome them. These gaps, once filled, may promote Mg alloys to become a stronghold for lightweighting, which will exceptionally benefit our environment and wellbeing.

A review on the effect of rare-earth elements on texture evolution during processing of magnesium alloys

Plastic deformation behavior of Mg89Zn4Y7 extruded alloy composed of long-period stacking ordered phase

It has recently been found that Mg97Zn1Y2 extruded alloy containing a long-period stacking ordered (LPSO) phase has superior mechanical properties. In this study, the high-temperature deformation mechanism of the Mg97Zn1Y2 extruded alloy was examined. Grain-boundary strengthening due to the refined Mg-matrix phase and fiber-like reinforcement due to the LPSO phase dominantly contribute to the strengthening of the alloy at room temperature, and they were confirmed to effectively act even at 200 °C. As a result, the extremely high strength of the alloy is maintained up to 200 °C, unlike other conventional Mg alloys. At 300 °C, however, the yield stress of the Mg97Zn1Y2 alloy largely decreases, and the orientation and the grain size dependence of the yield stress become weak. Increases in the operation frequency of non-basal slip in the Mg-matrix grains weaken the grain-boundary strengthening effect. In addition, the effect of fiber-like reinforcement due to the LPSO phase is also weakened at 300 °C because the window of microstructure suitable for inducing this effect becomes significantly narrow at this temperature.

High-temperature compressive deformation behavior of Mg97Zn1Y2 extruded alloy containing a long-period stacking ordered (LPSO) phase

Plastic deformation behavior of Mg97Zn1Y2 extruded alloys

Deformation mechanisms of Mg89Zn4Y7 (at.%) extruded alloy, which is mostly composed of LPSO-phase, was investigated focusing on their temperature dependence. The yield stress of as-extruded alloy showed extremely high value of ~480 MPa at RT, but it largely decreased to ~130 MPa at 300 °C. The decreasing rate of the yield stress could be significantly reduced, however, by the annealing of specimen at 400 °C, by suppressing the microyielding which is considered to occur related by the grain boundary sliding in restricted regions. The yield stress of the annealed specimens with random textures could be estimated by the Hall-Petch relationship by regarding the length of long-axis of plate-like grains as a grain size between RT and 300 °C. The yield stress of the annealed specimens maintained high values even at 200°C, but it also showed large decreases at 300 °C.

Akihito Kinoshita

Papers

Effect of long-period stacking ordered phase on mechanical properties of Mg97Zn1Y2 extruded alloy

Plastic deformation behavior of Mg89Zn4Y7 extruded alloy composed of long-period stacking ordered phase

High-temperature compressive deformation behavior of Mg97Zn1Y2 extruded alloy containing a long-period stacking ordered (LPSO) phase

Plastic deformation behavior of Mg97Zn1Y2 extruded alloys

Temperature Dependence of Compressive Deformation Behavior of Mg89Zn4Y7 Extruded LPSO-Phase Alloys