Structure and hardness evolution in nanocrystalline LIGA fabricated Ni-12 at%W alloy at 873 K

Nanocrystalline Ni-W alloys have good potential in LIGA fabricated MEMS. Thermal stability of Ni-12 at%W alloy prepared on silicon wafer using PMMA resist irradiated by synchrotron x-ray, as well as on copper is investigated. The grain size of Ni-12 at%W alloy increases from 21 nm to 31 nm upon heating at 873 K for 48 hours. Grain growth exponent is found to be 2.25, which indicates an insignificant role of grain boundary diffusion. The microhardness of the alloy decreases from 705 to 420 HV. Under the same heating condition, the hardness of sulphamate Ni decreases from 324 to 92 HV. The initial cross sectional banded microstructure of LIGA test microcomponent persists during heating at 873 K for 48 hours. A comparison with literature data on nanocrystalline Ni and Ni base alloys reveals that Ni-12 at%W alloy possesses a much more stable structure at 873 K. http://www.scopus.com/inward/record.url?eid=2-s2.0-53849145039&partnerID=40&md5=25886d73c700cb519d2e56f3216a8945