采用3种应变速率在不同温度下对一种奥氏体铁镍基合金进行拉伸实验, 结果发现在300-700℃范围内发生锯齿流变现象; 锯齿流变现象在300-600℃范围内表现为凸起式锯齿, 而在700℃时表现为下凹式锯齿; 此锯齿流变具有热激活性,即较高的拉伸温度使锯齿易于发生, 较大的拉伸速率则抑制其发生.对比分析室温(不发生锯齿流变)及400℃(显著发生锯齿流变)拉伸试样的微观组织,发现在400℃拉伸后的孪晶界上存在明显的位错塞积, 说明孪晶界可以有效地阻碍滑移变形,引起孪晶界附近应力积累, 从而导致了凸起式锯齿流变的发生. 孪晶界数量对锯齿波形的影响证实了此观点.
Tensile tests on a FeNi–base austenitic alloy, with different amount of twin boundaries, were conducted at different temperatures and three strain rates, respectively. The results show that serrated flow occurs at temperatures from 300 to 700 ℃. This serrated flow exhibits bulge–like serrations at temperatures from 300 to 600 ℃ and stress–loss serrations at 700 ℃, which manifests the nature of thermal activation, i.e. higher temperatures boost serrations and higher strain rates depress them. Investigations on samples deformed at room temperature (no serrated flow) and 400 ℃ (prominent serrated flow) indicate that twin boundaries are strong enough to block slip deformation at 400 ℃. As a result, stress accumulates on twin boundaries and bulge–like serrations appear on the tensile curves. Effect of twin boundary amount on the morphologies of serrations testified this mechanism.
[1] Le Chatelier A. Rev de Metall, 1909; 6: 914
[2] Zeides F, Roman I. Scr Metall, 1990; 24: 1919
[3] Zavattieri P D, Savic V, Hector Jr L G, Fekete J R, Tong W, Xuan Y. Int J Plast, 2009; 25: 2298
[4] Jiang H F, Zhang Q C, Yu Y H, Wu X P. Acta Metall Sin,2006; 42: 139
(江慧丰, 张青川, 徐毅豪, 伍小平. 金属学报, 2006; 42: 139)
[5] Fournier L, Savoie M, Delafosse D. J Nucl Mater, 2007; 366: 187
[6] Cottrell A H. Philos Mag, 1953; 44: 829
[7] Zhu S M, Nie J F. Scr Metall, 2004; 50: 51
[8] Prasad K, Varma V K. Mater Sci Eng, 2008; A486: 158
[9] Hale C L, Rollings W S, Weaver M L. Mater Sci Eng, 2001; A300: 153
[10] Shields J A, Goods S H, Gibala R, Mitchell T E. Mater Sci Eng, 1975; A20: 71
[11] Basinski Z S. Aust J Phys, 1960; 13: 354
[12] Onodera R, Era H, Ishibash T, Shimizu M. Acta Metall, 1983; 31: 1589
[13] Li X Y, Zhang J, Rong L J, Li Y Y. J Alloys Compd, 2009; 467: 383
[14] Michiuchi M, Kokawa H, Wang Z J, Sato Y S, Sakai K. Acta Metall, 2006; 54: 5179
[15] Mahajan S, Chin G Y. Acta Metall, 1973; 21: 173
[16] R´emy L. Acta Metall, 1977; 25: 711
[17] Jin Z H, Gumbsch P, Albe K, Ma E, Lu K, Gleiter H, Hahn H. Acta Mater, 2008; 56: 1126
[18] Qu S, Zhang P, Wu S D, Zang Q S, Zhang Z F. Scr Metall, 2008; 59: 1131
[19] R´emy L. Acta Metall, 1977; 25: 173
[20] Nembach E. Mater Sci Eng, 2006; A429: 277
