Brittle fracture grain boundaries

Also the character of fracture under the DF in corrosive medium is changed samples of steel Fe76.iCriiNiioMo2Tio.9 after HE with e < 5 have brittle intergranular fracture pattern with traces of plastic deformation at some grain boundaries. The initial (undeformed) state is typical of brittle fracture (trans- and intercrystalline one) with no indication of a plastic deformation. After HE with e >... 

Hydrogen embrittlement is the result of hydrogen that diffuses along the grain boundaries and combines with the carbon to form methane gas. The methane gas collects in small voids along the grain boundaries where it builds up enormous pressures that initiate cracks and decrease the ductility of the steel. If the metal is under a high tensile stress, brittle fracture can occur. 

Embrittlement by the segregation of impurity elements to grain boundaries leads to failure by fast fracture. A question that has been debated over hundred years is How can minute traces of bismuth cause this ductile metal to fail in a brittle manner Three hypotheses for this embrittlement exist. 

Ceramics are brittle, polycrystalline solids. For this family of materials, the fracture resistance is intimately related to the size and distribution of internal flaws or defects, which may occur near grain boundaries. Thus, reducing the grain size of alumina ceramics over the past 30 years (Table 6.2) has resulted in an overall improvement in its fracture strength. 

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