T. Takasugi et al., Influence of grain boundary composition on the moisture-induced embrittlement of Ni-3(Si,Ti) alloys, INTERMETALL, 7(5), 1999, pp. 543-551
Ni-3(Si,Ti) alloys containing different levels of boron were tensile tested
in air at room temperature at two different strain rates. The grain bounda
ry compositions and fracture modes of these alloys were determined by Auger
spectroscopy and scanning electron microscopy, respectively. Tensile elong
ation and fracture mode depend upon the fabrication procedure, heat treatme
nt, and strain rate. Widely different boron concentrations were observed at
the grain boundaries, depending on the fabrication procedure and heat trea
tment. In addition, silicon and titanium were depleted while nickel was enr
iched at the grain boundaries in all specimens examined. Tensile elongation
s correlated well with the grain boundary concentration of boron and also w
ith an embrittlement parameter defined as (Si+Ti-B)/Ti. A sharp brittle-duc
tile transition was found to occur with increasing grain boundary concentra
tion of boron and with decreasing values of the embrittlement parameter (Si
+Ti-B)/Ti. The critical grain boundary concentrations corresponding to this
transition were found to be sensitive to the strain rate. All the results
can be explained in terms of the effect of grain-boundary composition on mo
isture-induced environmental embrittlement. (C) 1999 Elsevier Science Ltd.
All rights reserved.