Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. ABSTRACT The interaction of 1/2<110> screw-and 60°dislocations with symmetric [110] tilt boundaries was investigated by atomistic simulations using many-body potentials representing a pure f.c.c. metal and ordered intermetallic compounds. The calculations were performed with and without an applied shear stress. The observations were: absorption into the grain boundary, attraction of a lattice Shockley partial dislocation towards the grain boundary and transmission through the grain boundary under the influence of a shear stress. It was found that the structural unit model may help to predict the interaction mechanism for long period boundaries and that the interaction in ordered compounds shows similarities to the interaction in f.c.c.metals. Some comparisons with experimental observations have been made.

No abstract

Abstract--The interaction between lattice dislocations and grain boundaries in Ni3A1 has been investigated by means of in situ TEM deformation experiments. The interaction between screw dislocations and a coherent twin boundary could be analyzed in detail. The interaction mechanism found experimentally was compared to the results of a computer modelling study. In the computer modelling study, many-body potentials representing Ni3A1 were used. The results of the in situ straining indicate that (110) screw dislocations impinging on a Z = 3 coherent twin boundary that have a Burgers vector that is parallel to the grain boundary plane can be transmitted to the symmetric slip plane in the other grain under influence of an applied stress. A one-to-one comparison with the results of a computer modelling study of exactly the same system in Ni3AI can be made and the experiment agrees with the simulations. Also, observations were made of superlattice intrinsic stacking faults (SISF) that were formed as a result of the interaction between gliding dislocations and the dislocations of a low angle grain boundary (cell wall). The creation of jogs in the line of the gliding dislocation may be the cause of the SISF formation.R~sum~-On 6tudie l'interaction entre les dislocations du r~seau et les joints de grains dans Ni3A1 au moyen d'essais de d&ormation in situ en MET. L'interaction entre les dislocations vis et un joint de macle coh6rent peut ~tre analys~e en d&ail. Le m~canisme d'interaction trouv6 exp6rimentalement est compar~ aux r6sultats d'une 6tude mod61is6e par ordinateur. Dans l'~tude mod6lis6e, on utilise des potentiels fi n corps pour repr6senter Ni3AI. Les r6sultats des d&ormations in situ montrent que les dislocations vis (110) qui rencontrent un joint de macle coh6rent Z = 3, ayant un vecteur de Burgers parall61e au plan du joint de grains, peuvent &re transmises sur le plan de glissement sym6trique de l'autre grain sous Faction de la contrainte appliqu~e. Une comparaison point par point avec les r6sultats de l'6tude num6rique du m~me systdme dans Ni3AI peut fitre effectu6e et l'exp6rience est en accord avec les simulations. De plus, on observe des d~fauts d'empilement intrins6ques de surstructure qui se sont form,s par suite de l'interaction entre les dislocations qui glissent et celles d'un joint de grains de faible d~sorientation (paroi de cellule). La cr6ation de crans sur la ligne de la dislocation qui glisse peut ~tre la cause de la formation d'un tel d6faut.Zusammenfassung--Die Wechselwirkung zwischen Gitterversetzungen und Korngrenzen in Ni3AI wird mit in-situ-Verformungsexperimenten im Durchstrahlungselektronenmikroskop untersucht. Die Wechselwirkung zwischen Schraubenversetzungen und einer koh~renten Zwillingsgrenze kann ausf/ihrlich analysiert werden. Der gefundene Wechselwirkungsmechanismus wird mit den Ergebnissen einer Computer-Modellstudie verglichen. In dieser werden Vielk6rperpotentiale, die das Ni3A1 darstellen, benutzt. Aus den Ergebnissen geht hervor, dab eine auf die koh~rente Zwillingsgrenze 2...

This paper describes a computer simulation study of the interaction between lattice dislocations and tilt grain boundaries. The calculations were camed out using a many-body potential for copper and potentials describing a stable L1, type of structure. Two interaction mechanisms were observed: absorption into the boundary by splittinginto D S c dislocations and splitting into lattice Shockley partial dislocations, one of which was incorporated in the boundary. If the associated step height for the DSC's is small and (one of) the DSC's can glide in the boundary plane, the lattice dislocation dissociates into DSc dislocations in the boundary. Otherwise, anotherreaction is favourable, like the incorporation of one lattice partial dislocation in the boundary.

No abstract