The effect of crystal geometry on the formation and crack development in molybdenum single crystals

Abstract

Ductile relaxation in cracked metal-organic chemical-vapor-deposition-grown AlGaN films on GaNThe systematic study of the defect structure evolution in single crystal specimens deformed in situ in the high voltage transmission electron microscope ͑HVTEM͒ was started around 1977 in the Baikov Metallurgy Institute of the USSR Academy of Sciences. All the experience gathered for the past 30 years has set up the basis for the determination of the way that metals adapt to the different physical factors inside the HVTEM column. In the present work the detailed phenomenology of the generation and propagation process of cracks in single crystals of Mo with different crystallographic orientations as well as the kinetics of opening of primary and secondary cracks and the tip evolution for cracks with different dislocation generation sources is presented.

Twinning-dominated nucleation, propagation and deflection of crack in molybdenum characterized within situtransmission electron microscopy

“…Accompanying the deflection of the crack tip, the crack surfaces display a zigzag morphology. The zigzag manner of crack propagation has been observed in metallic thin films of Mo, Ni 3 Ge and Ni 3 Al by transmission electron microscopy [16][17][18], and has been unambiguously ascribed to the alternation of primary and secondary slip systems. This alternation of dislocation slip systems reduces the film thickness intermittently and in turn produces the zigzag crack path [16].…”