Atomistic studies of the structure and composition of grain boundaries in Cu3Au and Ni3Al

Abstract

Abstract. In this paper we investigate the atomic structure and composition of grain boundaries in Cu3Au (weakly ordered compound) and Ni3AI (strongly ordered compound). Computer simulations employing both the molecular statics and Monte Carlo methods were performed and the Finnis-Sinclair type many-body central force potentials used. First, grain boundaries in stoiehiometric alloys are studied with the goal to investigate the impact of ordering strength on the grain boundary structure and composition. In Cu3Au grain boundaries may become compositionally disordered even at room temperature and the compositional disordering is associated with segregation of gold. In contrast, in Ni3A1 grain boundaries remain compositionally ordered up to very high temperatures. Secondly, the structures of grain boundaries and the effect of Ni and AI segregation in non-stoichiometric Ni3A1 are investigated. Nickel segregation leads to compositional disordering at grain boundaries, while aluminum segregation, which is strongly selective, leads to an ordered grain boundary structure with high AI content. The possible relationship between structural and compositional characteristics of grain boundaries and their mechanical properties, in particular the grain boundary brittleness and its alleviation by additional alloying, are then discussed in the light of the results of this study.

Temperature dependencies of the relaxation, order and segregation at a tilt grain boundary in

“…In the same temperature range, a sharp transition between grain boundary and bulk ordering properties occurs between planes at z = 4 and z = 6, and the disordered zone does not expand continuously from the grain boundary to the bulk as the temperature increases. This contrasts with the results given in [15] in the case of a = 29 boundary, thus showing that the strength of the coupling between the bulk and the boundary is dependent on the relative grain orientation. The temperature dependencies of the proper sublattice occupancy at the selvedge of the grain boundary are different.…”

“…This allowed us to cross check some of the results presented with ours, which is not often possible with computer simulation data. In the present work, we focus on the detailed thermal evolution of a grain boundary selected for its particularly large relaxation, segregation and disorder, rather than looking at common properties of several grain boundaries at selected temperatures as was done in [15] for different purposes.…”

“…L1 2 structures have already been the subject of many studies, motivated by, among other factors, the relationship between the strength of segregation and the mechanical properties of these compounds [15]. In [15], the authors compare the composition in a wide variety of grain boundaries in Cu 3 Au and Ni 3 Al at room temperature and somewhat below the temperature for the bulk order-disorder transition in Cu 3 Au.…”

Point defects in Cu2ZnSnSe4 (CZTSe): Resonant X‐ray diffraction study of the low‐temperature order/disorder transition

“…The small antiphase domains may arise due to the slow ordering kinetics (low temperature annealing) and low ordering energetics. Antiphase domain boundaries are well established in bimetallic alloys (with the classic case of Cu 3 Au), although the effect of the diffraction is much different [25]. Somewhat similar antiphase boundaries (stacking faults) have been reported but involve Sn site swapping with much larger domains [26].…”