Fracture, metals, intergranular tensile

Post-test metallographic examination of longitudinal sections of composite weld tensile samples provided data on the location of the fracture and the presence of secondary intergranular cracking. Base metal fracture locations were experienced with K-58 GTA welds at room temperature (RT), K-58 GTA/CW/PR (see Table II for notation) and K-58 GTA/CW/FR welds at all temperatures, Pyromet 538 GTA welds at all temperatures, Pyromet 538 SMA welds at RT, and A-286 GTA welds at RT. Weld FZ fractures were experienced with all 310S SMA welds, K-58 GTA welds below room temperature, K-58... 

In the presence of sufficient tensfle stress and traces of silicon, hot caustic solutions can induce see of boiler steels. This phenomenon is not called caustic embrittlement, as no loss of ductility occurs in caustic cracking. Tensile stress and caustic concentration cause the formation of continuous intergranular cracks in the metal. As the cracks progress, the strength of the metal is exceeded and fracture occurs. 

Not all metal.s and alloys can be persuaded to fracture in an intergranular manner by impact at low temperature. However, a whole group of metals and alloys will fracture in that mode if they are first embrittled by charging with hydrogen. Some will then fracture intergranularly by impact, but others require to be fractured by a slow tensile pull. This group includes the au.stenitic stainless steels [4], nickel [12], the nickel-base superalloys [14] and nickel aluminum alloys [45]. 

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