铍第一塑性高峰区的流变行为及本构方程

Flow behaviors and constitutive equation of the metal berylliumin the first plastic peak zone

摘要:

利用Instron5582万能材料试验机进行等温压缩试验,获得金属铍在变形温度为250 ℃~450 ℃、应变速率为10-1 s-1 ~10-4 s ?1 条件下的真应力?应变曲线,研究金属铍第一塑性高峰区的流变行为。结果表明：实验条件下金属铍的流变应力随应变速率的增大而增大,随变形温度的升高而减小,具有较大的温度敏感性。各变形条件下,金属铍加工硬化到一定程度后,随着应变量的增加,应力值有下降趋势,特别是250 ℃/10-1 s-1的变形条件,出现了明显的峰值应力。并且,随着应变量的增加,金属铍的变形激活能从244.95 kJ/mol 减少至166.82 kJ/mol,这些研究结果表明金属铍在第一塑性高峰区变形时,软化机制受动态再结晶的影响,但主要的软化机制仍是回复。建立了包含应变量的Arrhenius应变补偿本构方程,预测相对误差(MRE)最大为5.0550%,相关系数(R)最小为0.9899,能够较准确预测金属铍在第一塑性高峰区压缩变形时的流变应力。

Abstract:

The true stress-strain curve of the metal beryllium was obtained under deformation temperature of 250 ℃~450 ℃ and strain rate of 10_-1 ^s_-1^-10_-4 ^s_-1 by the isothermal compression testing which was conducted in the Instron 5582 universal material testing machine, and thus flow behaviors of the metal beryllium was studied in the first plastic peak zone. The results indicate that the flow stress of the metal beryllium increases with the increase of strain rate and decreases with the increase of deformation temperature under the experimental conditions. Furthermore, the flow stress is more sensitive to the variation of temperature. The flow stresses show a decreasing trend with the increase of strain after work hardening to a certain extent under various deformation conditions, especially 250 ℃/10_-1 ^s_-1^, theSflowSstressShasSaSpeakSvalue. Moreover, the deformation activation energy of the metal beryllium decreases from 244.95 kJ/mol to 166.82 kJ/mol as the strain increases. These results indicate that softening mechanism of the metal beryllium deformed in the first plastic peak zone is influenced by dynamic recrystallization, but the main softening mechanism is still recovery. It was established that an Arrhenius strain compensated constitutive equation that includes strain variables. The equation can accurately predict the flow stress of the metal beryllium during compression deformation in the first plastic peak zone, and the maximum mean relative estimation error (MRE) of the prediction is 5.0550%, and the minimum correlation coefficient (R) is 0.9899.