Effect of Extrusion Parameters on Mechanical Properties of Mg<SUB>97</SUB>Zn<SUB>1</SUB>Y<SUB>2</SUB> Alloys at Room and Elevated Temperatures

Abstract

The effects of alloy extrusion parameters, such as extrusion ratio, temperature, and speed on the mechanical properties at room and elevated temperatures and the microstructure evolution were investigated in the production of high strength Mg-Zn-Y alloys. The alloy used is a Mg 97 Zn 1 Y 2 (at%) which is engineered to acquire a long-period stacking ordered (LPSO) structure phase to increase alloy-strength. The microstructure of the extruded Mg 97 Zn 1 Y 2 alloy consists of hot-worked and dynamically recrystallized (DRXed) -Mg grains that includes a fiber-shaped LPSO phase elongated along the direction of extrusion. Whereas an increase in average equivalent strain promotes the DRX ofMg matrix and the dispersion of the fiber-shaped LPSO phase, an increase in average metal flow rate is conductive to the DRX of -Mg grains, but is not to the dispersion of LPSO phase. The mechanical properties of the extruded Mg-Zn-Y alloys are affected by changes in the area fraction of the DRXed grains and the dispersion of the fiber-shaped LPSO phase. As the extrusion ratio and extrusion speed increase, overall DRX bringing grain growth in its train in the -Mg matrix phase decreases the tensile strength of alloys, but the dispersed fiber-shaped LPSO phase remaining in the DRXed grains region makes good the adverse effect of overall DRX followed by grain growth.

Effect of Initial Grain Size on Microstructure and Mechanical Properties of Extruded Mg-9Al-0.6Zn Alloy

“…This suggests that the initial grain size of the billet has a negligible effect on the DRXed grain size of an extruded alloy, even though this is known to be strongly affected by extrusion parameters such as temperature and speed. [1,2] This insensitivity of the DRXed grain size to initial grain size is consistent with previous results obtained with Mg-3Al-1Zn alloy. [16] It can also be seen that there are a number of fine Mg 17 Al 12 precipitates (100 to 500 nm) distributed along the grain boundaries and within the grains of both samples (Figures 4(a) and (b)).…”

“…The microstructure and mechanical properties of extruded Mg alloys are known to be strongly dependent on extrusion variables; i.e., a decrease in deformation temperature, ram speed, and/or extrusion ratio generally results in a reduction in the size of dynamically recrystallized (DRXed) grains and a subsequent increase in strength. [1][2][3] In addition to these extrusion parameters, the microstructure of a billet prior to extrusion can also play an important role in determining the microstructure and mechanical properties of the final product. For example, twins initially present in a homogenized billet can increase the fraction of DRXed regions by acting as nucleation sites during extrusion, thereby improving the tensile properties of an extruded Mg alloy.…”

Plastic Deformation Behavior of Mg<SUB>12</SUB>ZnY LPSO-Phase with 14H-Typed Structure

“…[1][2][3][4][5][6][7][8][9][10][11][12] The strengthening mechanisms of Mg/LPSO two-phase alloys were recently discussed in detail, and it was reported that controlling the morphology and texture of the LPSO-phases is important 9,12) because the LPSO-phase exhibits strong plastic anisotropy. [13][14][15] Previously, we have examined the plastic deformation behavior of an LPSO-phase with a 18R-typed crystal structure.…”

Effect of Process Parameters of Backward Extrusion by Servo Press on Purification of A7075 Alloy under the Semisolid Condition

“…The average equivalent strain was calculated using the equation ε = lnR, 11) neglecting the shear deformation, where R is the extrusion ratio. From this equation, the average equivalent strain (ε ) was 1.1 for an extrusion ratio of 3 and 1.9 for an extrusion ratio of 7.…”