Macrostresses in sintered carbides

Effect of residual stresses on the strength of ceramic materials (Review)

“…Carbide, e.g., ZrC and NbC, billets are character ized by a significant difference between the chemical compositions in the surface layers and in the volume, and a significant gradient of α appears in them, which results in residual macrostresses in the absence of a [2][3][4][5][6]. Even an insignificant coeffi cient α gradient in high modulus carbides leads to the formation of high tensile stresses.…”

“…(The stresses related to volumetric changes should be almost relaxed.) Based on the results of studying the coefficient α gradient over the cross section of a billet using the well known depen dences of the thermal stresses on the properties [2,6], researchers obtained the following expression for the maximum residual stresses:…”

“…Macrostresses propagate over the entire volume or a significant part of a sample, mesoscopic stresses appear in a region of several grains in a polycrystal from several to several hundred microns in size, and microscopic stresses are localized inside one grain (several fractions of a micron). X ray diffraction analysis is used to measure all types of residual stresses [4][5][6][7][8][9]. For example, macrostresses are estimated from a shift in the positions of X ray dif fraction lines, mesoscopic stresses are estimated from the smearing and shift of the center of gravity of X ray diffraction lines, and microscopic stresses are esti mated from the radius of bending of extinction con tours in electron microscopic images [10] and using Raman spectra [11].…”

Development and characterization of Fe70Pd30 ferromagnetic shape memory splats

“…Still, in a rapidly solidified polycrystalline sample there are always contributions to the intrinsic stress by lattice distortions at defects. A quantification of the intrinsic microstress from the XRD diffractograms is difficult, as the peak width w is not only influenced by the microstress s inside the sample according to w ¼ E$ s 4tan q [24] (E is the elastic modulus of the sample), but also by the grain size according to the Scherrer-formula.…”