Bending properties of extruded AZ91–0.9Ca–0.6Y alloy and their improvement through precompression and annealing

Abstract

In this study, an extruded Mg–9Al–1Zn–0.3Mn–0.9Ca–0.6Y (AZXW9110) alloy is subjected to precompression and subsequent annealing (PCA) treatment for improving its bending formability, and the three-point bending properties of the as-extruded material and the precompressed and subsequently annealed (PCAed) material at room temperature are compared. During bending, microcracks formed in undissolved Al2Ca, Al2Y, and Al8Mn4Y particles propagate along the grain boundaries or twin boundaries and consequently form a macrocrack in the tension zones of the bending samples of both the materials. However, the bending formability of the PCAed material is 75% higher than that of the as-extruded material owing to the promoted twinning and slip behaviors in the former. The as-extruded material has a strong normal direction (ND) texture and a weak transverse direction (TD) texture, and the ND- and TD-oriented grains are unfavorable for both {10–12} twinning and basal slip in the tension zone of the bending sample of this material, which eventually results in its low bending formability. The PCAed material has a strong extrusion direction (ED) texture, weak TD texture, and spread ND texture. During bending, {10–12} twins are fully formed in the ED-oriented grains, and this {10–12} twinning effectively accommodates the plastic strain in the tension zone. In addition, the activation of basal slip in the ND-oriented grains of the PCAed material is promoted owing to the spread ND texture of this material. Consequently, this material exhibits substantially superior bending formability because of the vigorous {10–12} twinning in its ED-oriented grains and promoted basal slip in its ND-oriented grains.

Keywords

• Magnesium
• Bending
• Formability
• Twinning
• Texture