Abstract Positron lifetime parameters have been measured by position annihilation technique in binary Ni7777Al2323 and Ni7474 Al2626 alloys with different Al contents and Ni33Al alloy doped with different amounts of Zr. The density o f free electrons in bulk materials and grain boundaries was calculated in this p aper. The results show that the density of free electrons in bulk materials and grain boundaries in Ni7474Al2626 alloy is lower t han that in Ni7777Al2323 alloy. The open volume in grain boundary is larger in Ni7474Al2626 alloy, and the cohesion of grain boundaries is weaker. When an amount of Zr atoms is added into the Ni33Al alloy, they increase the density of f ree electr ons in the bulk and thus increase the bonding cohesion in the bulk. The other Z r atoms will segregate at grain boundaries and increase their free electron dens ity; this will strengthen the bonding cohesion in grain boundaries. Alloying ele ment Zr is found to be beneficial to reduce the brittleness of Ni33Al alloy with different Al contents.
Guo Jian-Ting,Li Yu-Fang,Xiong Liang-Yue et al. The micromechanism of alloying element Zr affecting the ductility of Ni33 sub>Al alloy with different Al contents. Acta Phys. Sin., 2005, 54(4): 1868-1873.