AZ31マグネシウム合金板の温間非比例成形限界ひずみとその解析的予測

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Magnesium alloy usually exhibit low ductility at the room temperature due to its hexagonal close-packed structure, but it will be improved at elevated temperature. Therefore, warm press-forming for magnesium ally sheets is quite attractive. In order to determine the optimum condition of press-forming for magnesium alloy sheets, in the present work, the effects of temperature, strain-rate and non-proportional deformation on forming limit diagram (FLDs) were experimentally investigated. The pre-strain of 1/3 and 2/3 in the forming limit were added to equi-biaxial direction of the magnesium alloy sheets (AZ31). The non-proportional FLDs of a magnesium alloy (AZ31) sheet was obtained by performing punch stretch-forming tests at various forming speeds (3, 30 and 300mm・min-1) at temperatures of 100, 150 and 250℃. The temperature and strain-rate dependency were confirmed for non-proportional deformation forming limit strain by the given in the direction of equi-biaxial strain of the magnesium alloy sheet. Theforming limit strain experimentally showed becoming small by quickening of the speed and increases by rising of the temperature. Because the amount of the limit equivalent plasticity strain in the direction of a plane strain had already been exceeded, the specimen was broken at once in the plane strain forming. Non-proportion FLD is predictable in the condition with low ductility by "Limit equivalent plasticity strain that depends on the direction of the final strain". On the other hand, the limit strain predict in this Criterion was smaller than the experiment value in a high temperature and a low-speed condition. A viscous deformation influenced in a high temperature and a low-speed condition and the appeared this influenced the increase of ductility strongly.
2008-02-28

AZ31マグネシウム合金板の温間非比例成形限界ひずみとその解析的予測

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