Anomalous softening behavior in Ti/Ni multilayers with ultra-high hardness

作者：Shi, J.; Cao, Z. H.; Wei, M. Z.; Pan, G. J.; Xu, L. J.; Meng, X. K.^*

来源：Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing, 2014, 618: 385-388.

DOI：10.1016/j.msea.2014.09.019

• Ti/Ni multilayer
• Modulation period
• Nanoindentation
• Pop-in

We utilize alloying of Ti/Ni multilayers to prepare Ti-Ni alloy films and investigate effects of modulation period (lambda) on the alloying and mechanical properties. It is found that the annealed multilayers with the lambda of 2.7-54 nm exhibit ultra-high hardness, far exceeding co-sputtering Ti-Ni alloy films, and the maximum hardness is found at lambda=5.4 nm. Attractively, another anomalous hardness softening occurs at lambda of 13.5 and 27 nm with increase of indentation depth besides the softening at lambda=5.4 nm, which is simultaneously accompanied by the pop-in events including displacement jumps and sudden drop of load. The pop-in events are attributed to stress-induced martensitic phase transformation and the critical load for martensitic transformation increases with the decrease of lambda.

• 出版日期2014-11-17
• 单位固体微结构物理国家重点实验室; 东华理工大学; 南京大学