为了研究变形镁合金AZ31B管材的热态内压成形性能,通过单向拉伸测试了不同温度和应变速率下其力学性能的变化,通过胀形实验研究了温度对内高压成形性能的影响,以及相应变形条件下微观组织的变化.实验结果表明:在20～300℃时,AZ31B的屈服强度和抗拉强度随着温度的升高而降低,总伸长率随着温度的升高而提高,均匀伸长率随着温度的升高先增大后减小;当应变速率在0.001～0.1~(-1)时,屈服强度和抗拉强度随应变速率的增大而升高,总伸长率随着应变速率的增大而减小,均匀伸长率随着应变速率的增大先增加后减小;当温度在20～250℃时,镁合金管材的极限胀形率随温度的升高先增大后减小,在175℃时达到最大值.微观组织观察表明,175℃下不完全动态再结晶和孪晶两种微观组织的出现是使镁合金管材极限胀形率提高的主要原因.
To study the formability of an AZ31B magnesium alloy tube in warm hydroforming, its mechanical properties in state of one-direction stress were investigated by warm tensile tests. Its hydroformabilities at different temperatures were obtained by warm bulging experiments. And the microstructures before and after deformation were analyzed. The experimental results show that, when the temperature is between 20 ℃ and 300 ℃, the yielding strength and the tensile strength are decreased with the ascending temperature, while the total elongation of the magnesium alloy tube is decreased, and the uniform elongation is increased before 175 ℃ and decreased after 175 ℃. When the strain velocity is between 0. 001 s~(-1) and 0. 1 s~(-1), the yielding strength and the tensile strength are increased with the ascending strain velocity, while the total elongation of the magnesium alloy tube is decreased, and the uniform elongation is increased before 0. 01 s~(-1) and decreased after 0. 01 s~(-1). The expansion ratio of the magnesium alloy tube is increased as the temperature ascends from 20 ℃ to 175 ℃ , and is decreased as the temperature ascends from 175 ℃ to 250 ℃. Incomplete dynamic re-crystallization and twin can be observed on the bulged tube at 175 ℃, which enhances the magnesium tube's plasticity.
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