Effects of be and fe content on plane strain fracture toughness in A357 alloys |
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Authors: | Yen-Hung Tan Sheng-Long Lee Yu-Lom Lin |
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Affiliation: | (1) Department of Mechanical Engineering, National Central University, 32054 Chung-Ti, Taiwan, Republic of China;(2) Division of Metallurgy, Chung-Shan Institute of Science and Technology, 325 Lung-Tan, Taiwan, Republic of China |
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Abstract: | The effect of Be and Fe content on the plane strain fracture toughnessK
IC of aluminum-based A357 alloys is investigated. The fracture behavior of A357 alloys has been evaluated as a function of both
the magnitude and morphology of iron-bearing compounds and silicon particles. Addition of Be is beneficial for tensile properties
and fracture toughness in the case of alloys containing intermediate (0.07 pct) and higher (0.15 pct) Fe levels. On the other
hand, Be added to alloys containing the lower Fe (0.01 pct) level appears detrimental to tensile strength, but the quality
index, notch-yield ratio (NYR), and plane strain fracture toughness were improved. Fractographic analysis reveals that crack
extension of A357 alloys occurs mainly in an intergranular fracture mode. The fracture processes are initiated by void nucleation
at iron-bearing compounds or irregularly shaped eutectic silicon particles as a result of their cracking and decohesion from
the matrix. Then, void growth and coalescence result in growth of the main crack by shear-linkage-induced breakdown of submicronstrengthening
particles. The effect of Be on increasingK
IC is more apparent in the higher Fe alloys than in the lower Fe alloys. Superior toughness obtained by microstructural control
has also been achieved in the intermediate and higher Fe levels of Be-containing alloys, with values equal to those obtained
in alloys of lower Fe content. |
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