Fracture Toughness in an Extruded ZK60 Magnesium Alloy

Abstract

Examination of fracture toughness has been performed a commercial Mg-Zn-Zr alloy, ZK60, with fine strengthening particles. The commercial alloy was extruded at 633 K, and then heat treated at specific conditions. The microstructures were equi-axed grains, and average grain size and precipitate size were 11.6 mm and 50-150 nm, respectively. The yield strength and elongation-to-failure were 225 MPa and 17.0%. The plane-strain fracture toughness, K IC , was estimated to be 20.6 MPam 1=2 in stretched zone analysis. From ductile fracture model, all the finer particles did not affect the void formation. The precipitates having a large diameter, more than 100 nm, were supposed to be the origin of void formation.

Synergetic Effect of Grain Refinement and Spherical Shaped Precipitate Dispersions in Fracture Toughness of a Mg-Zn-Zr Alloy

“…4,6,[10][11][12]18) It is found that the present alloy has a good balance of strength and toughness, which shows a higher strength-toughness than that of conventional wrought magnesium and magnesium alloys. In general, the fracture toughness of magnesium is affected by the grain size.…”

“…[13][14][15] In magnesium alloys, the existence of precipitates also influences the fracture toughness as in conventional alloys. [16][17][18] It has been reported that the spherical shaped precipitate is more effective for improving the fracture toughness than the rod shaped precipitates, 17) since they are more effective in the pinning of dislocations. On the other hand, a precipitate with a large diameter becomes easily the site of fracture, because of a creation of large strain field around these precipitates.…”

“…On the other hand, a precipitate with a large diameter becomes easily the site of fracture, because of a creation of large strain field around these precipitates. 18) Thus, controlling the precipitate morphology such as shape and/or size is also important to improve the fracture toughness. Therefore, the Mg-Zn-Zr alloy, where precipitates are formed easily, was used in this study to examine the synergetic effect of microstructure controls of grain refinement and the dispersion of spherical shaped precipitates on the fracture toughness.…”

High Strength and Fracture Toughness Balances in Extruded Mg-Zn-RE Alloys by Dispersion of Quasicrystalline Phase Particles

“…20) On the other hand, in general, the particles have been known to affect the fracture toughness, because they become the void nucleation site due to the creation of a large strain field around them. The dispersion of a large size 21) and/or a high volume fraction of particles 22) are not effective, and the alloys containing these particles cause lower fracture toughness. Thus, understanding the role of the particles is important for improving the fracture toughness.…”

Effects of Hydrogen on the Mechanical Properties of Pure Magnesium

“…1) One of the effective ways for improving the ductility and fracture toughness of Mg alloys is grain refinement 2,3) because it promotes the prismatic hai slips, 4) and it facilitates the creation of a large plastic zone ahead of the fracture precrack. 5,6) In addition, the control of texture 7) and the control of size and distribution of precipitates 8) are effective for the enhanced ductility and fracture toughness.…”