Monotonous and cyclic creep in a heat-resistant 16Cr10W4MoTiAl nickel-based alloy—transmission electron microscopy study of microstructure

A transmission electron microscopy (TEM) study of the dislocation structure developed in a nickel-based 16Cr10W4MoTiAl heat-resistant alloy was performed. Specimens subjected to monotonic or cyclic creep at 1023 K were investigated. Two distinctly different arrangements of dislocations were found after monotonic creep. At low applied stresses, numerous dislocation loops around γ′ particles indicate that the motion of dislocations is strongly influenced by γ′ precipitates. In the range of high applied stresses, pronounced slip bands form which are composed of several closely spaced {111 slip planes. The cutting of γ′ particles by dislocations is observed frequently and the dislocation motion does not seem to be considerably hindered by precipitates. The distribution of dislocations after cyclic creep can be characterized as a mixture of the dislocation structures representative of low and high applied stress regions in monotonic creep. Two different dislocation arrangements are discussed in terms of the creep mechanism and the response of the alloy to cyclic creep loading.