Abstract
In the present work, the effect of heat treatment on the cyclic deformation behavior of as-extruded ZA81M magnesium alloy was investigated. Two heat treatment conditions were applied to the as-extruded ZA81M alloy: a solution treatment (T4, 653 K for 40 h and quenched with 298 K water) and a solution treatment plus artificial aging (T6, 348 K for 32 h (pre-aging at low temperature) and 453 K for 8 h (the second aging) and quenched with 353 K water). The results showed that the fine second phase precipitated after the aging treatment, the tensile yield strength of the T6-treated specimens increased, and the stress amplitude of T6-treated specimens was always higher than that of T4-treated specimens. The T6-treated specimens had a higher total strain energy density and a shorter fatigue life at a strain amplitude of 0.4%, and a lower total strain energy density and a longer fatigue life at a strain amplitude of 0.8%, compared to the T4-treated specimens. All fatigue cracks of the T4 and T6 ZA81M alloy were initiated at the second phase or along the grain boundary and propagated perpendicular to the loading direction.
Highlights
Magnesium alloys, as the lightest metal structural materials, are important lightweight materials used in the transportation, electronic communications, aerospace, and defense industries [1,2,3]
Lee et al [4] observed the cyclic deformation behavior in situ by neutron diffraction and reported that, for tension followed by reverse compression, little detwinning occurs after the initial tension stage, but almost all of the twinned volumes are detwinned during loading in reverse compression
Tensile yield strength was increased to 296 MPa and the elongation was decreased to 18.5% after subsequent aging treatment, which gave a similar result to the ZK60 magnesium alloy subjected to T4 aging treatment, which gave a similar result to the ZK60 magnesium alloy subjected to T4 and T6 heat treatments [16]
Summary
As the lightest metal structural materials, are important lightweight materials used in the transportation, electronic communications, aerospace, and defense industries [1,2,3]. In order to improve the service reliability and fatigue life of structural components and devices, the cyclic deformation behavior of magnesium alloys needs to be investigated. Wang et al [15] investigated the anisotropic cyclic deformation behavior of extruded ZA81M magnesium alloy with a tilted basal texture and found that there were obvious asymmetries in the cyclic deformation along extrusion direction and transverse direction. Our investigations into this alloy indicated that because numerous high-density nano precipitates formed in the ZA81M alloy during heat treatment, the tensile properties of as-cast and as-extruded ZA81M alloy were markedly improved. ZA81M magnesium alloy bar was investigated and an analysis of T4 and T6 samples was carried out in order to clarify the role of the heat treatment in the initiation and propagation of fatigue cracks, and reveal the mechanism of nano precipitate in fatigue failure
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