Grain boundaries strength

Ikuhara, Y., Yoshida, H., and Sakuma, T., Impurity effects on grain boundary strength in structural ceramics , Mater. Sci. Eng., 2001, A319-321, 24-30. 

The reason for this enhanced demand for powder purity originates in the fiict that remaining impurities after sintering greatly affect the woikability (grain boundary strength, reciystallization temperature, etc.) and properties of the final product. 

The significant decrease in microhardness and wear resistance of the X-ray amorphous films in comparison with nanocrystalline films is also observed (Fig. 1). Probably, this is related to the dependence of the material hardness on the grain boundary strength and deformation strength. For nanometer-scale grain size the diffusion slip plays an important role even at room temperature, increasing the deformation rate [7]. 

Compresave yield stress estimations from Grain boundary strength, <7 1, for sintered alumina (grain size D 1-5 pm) with grain boundary fracture touglmess [7] ss 1.5 MPa m, size of defects (e.g. pores at triple junctions)... 

For optimum toughening by crack deflection Telle et al. [145] pointed out that geometric factors like grain size, volume fraction, orientation and morphology of the added or in situ grown phases as well as the grain boundary strength have to... 

In addition to a relation of the average peak-to-valley height and the vibrational amplitude, there is also a relation to the material to be machined (Haas, 1988). Hilleke (1998) assumes here an influence of the structural properties grain size and grain boundary strength. 

The other measures of grain-boundary strength then follow ... 

Atomic size must be included when considerations are given as to whether an clement will embrittle a metal or alloy. In general, large atoms decrease the grain boundary strength while small atoms increase it 129. Thus, in the case of iron and steel, atoms such as S, P, Sn, Sb and As. which are all larger than Fc. tend to make a steel more brittle (that is. lower its ductile-to-brittle transition temperature), while small atoms such as B, Be and C. which are smaller than Fe. tend to make the steel less brittle. 

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