The microstructure behavior during high temperature deformation of Ni-base alloys based on alloy 690 modified with Nb, Mo, and Hf additions were studied. Optical and electron microscopy were used to characterize these materials and the results were compared with Calphadbased modeling results. The alloys behavior was studied between 500 and 1000 °C using an in-situ high temperature deformation test. The role of precipitates on the grain boundary morphology and their effect on grain boundary sliding and the mechanism of ductility-dip cracking are discussed. Both, undulated grain boundaries and primary intra-granular precipitates improved the alloy DDC resistance. © 2012 Trans Tech Publications, Switzerland.706-709 945950The Minerals, Metals and Materials Society (TMS),NSFArkoosh, M.A., Fiore, N.F., (1972) Metallurgical Transactions, 3, p. 2235Rhines, F.N., Wray, P.J., (1961) Transactions of the ASM, 54, p. 117Haddrill, D.M., Baker, R.G., (1965) British Welding Journal, p. 411Ii Noecker, F.F., Dupont, J.N., (2009) Welding Journal, 88, p. 7Nissley, N.E., Lippold, J.C., (2009) Welding Journal, 88, p. 131Ramirez, A.J., Lippold, J.C., (2004) Mat. Sci. and Eng. A, 380, p. 259Gifkins, R.C., (1994) Materials Characterization, 32, p. 59Langdon, T.G., (2006) Materials Science, 41, p. 597Ramirez, A.J., Lippold, J.C., (2005) Hot Cracking Phenomena in Welds, p. 19. , edited by T. Böllinghaus, H. HeroldCollins, M.G., Ramirez, A.J., Lippold, J.C., (2004) Welding Journal, 83, p. 39Yamaguchi, S., (1980) Phil. Trans. R. Soc. Lond. A, 295, p. 122Ramirez, A.J., Garzón, C.M., (2008) Hot Cracking Phenomena in Welds, 2, p. 427. , edited by T. Böllinghaus, H. Herold, C. Cross, J.C. LippoldZimina, L.N., Burova, N.N., Makushok, O.V., (1986) Met. Sci. and Heat Treatment, 28 (2), p. 130Duhl, J.M., Sullivan, C.P., (1971) Journal of Metals, pp. 38-40Torres, E.A., Paternella, F.G., Caram, R., Ramirez, A.J., (2009) 8 th International Conference on Trends in Welding Research, p. 354. , Pine-Mountain, GA-USAUnfried S, J., (2010) Mathematical Modelling of Weld Phenomena, 9, p. 983. , edited by Maney. H CerjakH K D H Bhadeshia and E KozeschnikPigrova, G.D., (2005) Metal Science and Heat Treatment, 47 (11-12), p. 544Torres, E.A., Caram, R., Ramirez, A.J., (2010) Materials Science Forum, 638-642, p. 2858Unfried S, J., Torres, E.A., Ramirez, A.J., (2011) Hot Cracking Phenomena in Welds, 3. , edited by T. Böllinghaus, H. Herold C. Cross, in pressAfonso, C.R.M., Lippold, J.C., Ramirez, A.J., (2010) Metallurgical Transactions A, , submitted to