Effect of Precipitates in Mg−Sm Alloys on Their Deformation Behavior and Yield Asymmetry

Abstract

The strengthening effect of precipitates in a Mg−0.4Sm (wt%) alloy on dislocation slip and extension twinning (ET) is evaluated by experimental work and viscoplastic self‐consistent (VPSC) modeling. Experimental results reveal that the extruded Mg−Sm alloy consists of rare‐earth texture (<−12−11> // ED) and extrusion texture (<−12−10> // ED) components. After aging precipitation, tensile yield stress is more effectively enhanced than compressive yield stress. Transmission electron microscopy (TEM) analysis confirms that the precipitates in the aged Mg−Sm alloy are of β′ with an orthorhombic crystal structure. The introduction of β′ precipitates in the compression sample stimulates a higher fraction of extension twins. VPSC modeling indicates that the critical‐resolved shear stresses (CRSS) for prismatic slip, pyramidal <c + a> slip, and basal slip are increased by 75, 30, and 6 MPa, respectively, by aging precipitation, while the precipitation strengthening on ET is negligible. By preferentially hardening against prismatic slip, the compressive and tensile yield asymmetry are increased for the aged Mg−Sm alloy.

A Strain Rate‐Dependent Constitutive Model for Asymmetric Hardening Behavior of TB9 Titanium Alloy

“…However, a phenomenon is often observed that some materials have different flow stresses between tension and compression, and it is defined as the strength differential effect or asymmetric yielding. [15][16][17] Concerning the constitutive modeling of the different metals and alloys, most attention has been devoted to the asymmetric yielding and hardening type. [18,19] Stoughton and Yoon [20] described the strength differential effect of sheet metal forming The TB9 titanium alloy is one of the most promising materials for engineering application due to high strength, high toughness, and corrosion resistance.…”