R.A. Padgett

Surface and grain boundary segregation in relation to intergranular fracture: Boron and sulfur in Ni3Al☆

Unlike most solutes that segregate to grain boundaries, we have observed that boron segregates more strongly to grain boundaries than to free surface in Ni/sub 3/Al. This observation, along with the previously reported beneficial effect of boron segregation on grain boundary strength, is in qualitative agreement with a theory of grain boundary cohesion first put forward by Rice. If similar studies of other beneficial grain boundary segregants bear out this initial agreement with Rices theory, our understanding concerning the nature of segregation effects on grain boundary cohesion could be significantly enhanced.

Comparison of grain boundary compositions in B-doped and B-free Ni3Al

Analyse par spectrometrie Auger de la composition des joints dans les alliages Ni-24 et 25,2 Al contenant ou non 0,24 B.Pour les alliages libres de bore,les joints se trouvent enrichis en Al ou Ni suivant la teneur en aluminium.Pour les alliages contenant du bore,les joints presentent la meme composition que les alliages sans bore.Ceci montre une forte tendance a la cosegregation B-Ni.

Boron segregation at grain boundaries in rapidly solidified Ni3Al

The work reported here was performed to test the suggestion that the suppression of beneficial boron segregation to grain boundaries as a result of the increasing quench rate was responsible for the ductile-to-brittle transition on increasing solidification rate. Auger analysis and scanning electron microscopy of the fractured surfaces were the primary methods used. Auger spectroscopy results show along with previous work on bulk materials, that the critical concentration for strengthening grain boundaries is between 7 to 11 at. % B.

Effects of Sb, Sn, As, and P additions on the high-temperature ductility of Ni☆

This note reports low strain rate, 600/degree/C tensile test results on four single phase Ni-metalloid alloys and two undoped control heats of Ni. The four metalloid dopants (Sb, Sn, As, and P) were chosen because they are known to segregate to internal interfaces in Ni and/or Fe and they have large solid solubilities in Ni at 600/degree/C. Sb and Sn are the two most potent embrittlers, with As having an intermediate effect, and P inducing no intergranular cracking. 9 refs.

The concentration dependence of CD diffusivity enhancement in dilute PBCD alloys

Solute diffusivity enhancement techniques were used to provide experimental evidence for the existence of interstitial-substitutional solute pairs. Diffusion of Cd in Pb--Cd alloys is thought to represent the substitutional extreme of the dissociative equilibrium.