TY - JOUR
T1 - Mechanical strength and failure characteristics of cast Mg-9%Al-1%Zn alloys produced by a heated-mold continuous casting process
T2 - Fatigue properties
AU - Okayasu, Mitsuhiro
AU - Takeuchi, Shuhei
N1 - Funding Information:
This work was financially supported by a grant (Young Scientists (B)) from the Japanese Government (Ministry of Education, Science, Sports and Culture) and by Ehime University .
PY - 2014/4/10
Y1 - 2014/4/10
N2 - The fatigue properties and failure characteristics of a cast Mg alloy (AZ91: Mg-Al8.9-Zn0.6-Mn0.2) produced by heated-mold continuous casting (HMC) and conventional gravity casting (GC) are investigated. Excellent fatigue properties are obtained for the HMC alloy compared with the GC alloy. The high fatigue strength of the HMC alloy is a reflection of its improved microstructural characteristics, namely, tiny α-Mg grains and fine spherical eutectic structures (β-Mg17Al12). Fatigue cracks propagate mainly in the α-Mg grains and along high-hardness β-phases in both alloys. The direction of fatigue crack growth is altered as the crack reaches the eutectic phases. Because the tiny eutectic phases are distributed randomly in the HMC alloy, a meandering crack path is formed, which results in high crack growth resistance, leading to the high fatigue strength. For the HMC alloy, a striation-like failure mode can be seen in the crack growth stage, and dimple fracture is the dominant feature in the final failure stage. On the other hand, cleavage-like brittle failure with many microcracks can occur in the GC alloy. Severe lattice strain occurs during the final failure stage, especially for the HMC alloy, resulting in strong work hardening, although this is weak in the crack growth site. Severe strain is distributed uniformly around the entire cracks in the HMC alloy when the sample is fractured by monotonic loading. The lattice strains in the HMC alloy under monotonic and cyclic loading are overall higher than those in the GC alloy, owing to the high material ductility of the HMC alloy.
AB - The fatigue properties and failure characteristics of a cast Mg alloy (AZ91: Mg-Al8.9-Zn0.6-Mn0.2) produced by heated-mold continuous casting (HMC) and conventional gravity casting (GC) are investigated. Excellent fatigue properties are obtained for the HMC alloy compared with the GC alloy. The high fatigue strength of the HMC alloy is a reflection of its improved microstructural characteristics, namely, tiny α-Mg grains and fine spherical eutectic structures (β-Mg17Al12). Fatigue cracks propagate mainly in the α-Mg grains and along high-hardness β-phases in both alloys. The direction of fatigue crack growth is altered as the crack reaches the eutectic phases. Because the tiny eutectic phases are distributed randomly in the HMC alloy, a meandering crack path is formed, which results in high crack growth resistance, leading to the high fatigue strength. For the HMC alloy, a striation-like failure mode can be seen in the crack growth stage, and dimple fracture is the dominant feature in the final failure stage. On the other hand, cleavage-like brittle failure with many microcracks can occur in the GC alloy. Severe lattice strain occurs during the final failure stage, especially for the HMC alloy, resulting in strong work hardening, although this is weak in the crack growth site. Severe strain is distributed uniformly around the entire cracks in the HMC alloy when the sample is fractured by monotonic loading. The lattice strains in the HMC alloy under monotonic and cyclic loading are overall higher than those in the GC alloy, owing to the high material ductility of the HMC alloy.
KW - Continuous casting
KW - Failure characteristic
KW - Fatigue property
KW - Magnesium alloy
KW - Microstructural characteristic
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U2 - 10.1016/j.msea.2014.01.098
DO - 10.1016/j.msea.2014.01.098
M3 - Article
AN - SCOPUS:84896823707
VL - 600
SP - 211
EP - 220
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
SN - 0921-5093
ER -