J jog Step in a dislocation line perpendicular to its slip plane. Jogs of the height equal to one interplanar spacing (called elementary jogs) can occur either as a result of the dislocation intersection with a forest dislocation or due to the dislocation climb. Jogs of the edge type on screw dislocations can also form during double cross-slip, the jogs being several interplanar spacings high (called multiple jogs). The edge-type jogs on screw dislo - cations impede their glide because the jogs can only climb. Johnson–Mehl–Kolmogorov equation Description of transformation kinetics, assuming that: nucleation is homogeneous; the nucleation rate, , is independent of time; and the linear growth rate of new crystallites, G, is constant and isotropic. In this case, the kinetic equation is: where V and V 0 are the transformed and initial volumes, respectively, and t is the transformation time. Compare with Avrami equation. N · VV 0 ⁄ 1 π N · G 3 t 4 –3⁄()exp–= © 2003 by CRC Press LLC J jog Step in a dislocation line perpendicular to its slip plane. Jogs of the height equal to one interplanar spacing (called elementary jogs) can occur either as a result of the dislocation intersection with a forest dislocation or due to the dislocation climb. Jogs of the edge type on screw dislocations can also form during double cross-slip, the jogs being several interplanar spacings high (called multiple jogs). The edge-type jogs on screw dislo - cations impede their glide because the jogs can only climb. Johnson–Mehl–Kolmogorov equation Description of transformation kinetics, assuming that: nucleation is homogeneous; the nucleation rate, , is independent of time; and the linear growth rate of new crystallites, G, is constant and isotropic. In this case, the kinetic equation is: where V and V 0 are the transformed and initial volumes, respectively, and t is the transformation time. Compare with Avrami equation. N · VV 0 ⁄ 1 π N · G 3 t 4 –3⁄()exp–= © 2003 by CRC Press LLC K Kelvin’s tetrakaidecahedron See tetrakaidecahedron . Kê peak/relaxation Internal friction peak induced by a viscous behaviour of grain boundaries connected with grain-boundary sliding . Kerr microscopy Technique for observing domain structures by means of polarized-light microscopy . Magnetic domains are visible because the interaction of polarized light with the magnetized matter rotates the polar - ization plane of reflected light by an angle dependent upon the magneti- zation direction . Kikuchi lines Nearly straight, black lines and white lines in electron diffraction patterns received from relatively thick foils. They result from diffraction of nonelastically scattered electrons. Kikuchi lines are used for a precise determination (with an accuracy better than 1°) of lattice orientation. kinetics [of transformation] Time dependence of the volume fraction trans- formed. The term relates not only to phase transitions, but also to recrystallization. Kinetics of thermally activated reactions are usually described either by the Johnson–Mehl–Kolmogorov equation or the Avrami equation. kink A step of one interatomic spacing length in a dislocation. Unlike jogs, it lies in the slip plane of the dislocation. Kinks can occur by thermal activation as, e.g., double kinks connecting two parallel segments of the same dislocation lying on both sides of the Peierls barrier. Kinks can easily glide along with the dislocation. kink band Part of a plastically deformed grain. The lattice inside the band is disoriented relative to the lattice of the grain parts outside it. In contrast to deformation bands, the disorientation inside kink bands is rather small, if any. Kink bands are frequently observed in HCP metals sub - jected to compression. Kirkendall effect Manifestation of the difference in diffusion rates of the atoms of different components in the case of vacancy mechanism, i.e., in substitutional solid solutions. An annealing of a sample made of two closely contacting parts of different compositions results in the follow - ing. First, the interface between these parts shifts into the part with the higher intrinsic diffusivity (just this is known as the Kirkendall effect). Second, since the atomic flux is equivalent to the vacancy flux in the © 2003 by CRC Press LLC L laminar slip Stage of plastic deformation of a single crystal in which only one slip system is active. See also easy glide. Lankford coefficient See -value. large-angle grain boundary See high-angle grain boundary. Larson–Miller parameter Empirically found quantity, P, used for the extrapo- lation of the creep-rupture data obtained on a definite material at a certain temperature, T: P = cT (A +B ln t) where c, A, and B are empirical coefficients, and t is the creep-rupture life. The extrapolation is valid only for the same material and an identical stress state. latent hardening Decreased deformation, if any, on one or more slip systems having the same Schmid factor as the active slip system. Latent hardening results from the inhibition of the dislocation glide motion, as well as from the blocking of the dislocation sources on the systems with low deforma - tion, both caused by a stress field produced by dislocations on the active slip system. lath martensite Product of martensitic transformation in low- to medium-car- bon steels with a relatively high M s temperature. The martensite crystal- lites have an appearance of tightly arranged, thin (<1 µm) laths separated by low-angle boundaries. The laths are characterized by the habit plane {111} A , whereas their lattice is oriented with respect to the austenite according to the Kurdjumov–Sachs orientation relationship. The laths form packets with jugged boundaries. The substructure of lath martensite is characterized by high density of dislocation tangles. Lath martensite is also called packet, blocky, or massive martensite. lattice See crystal lattice. lattice basis Group of atoms belonging to a lattice point. Translations of lattice basis along 3 crystal axes build the corresponding crystal structure. If the group consists of one atom, the basis is denoted by the coordinates of the atoms at the origin and inside the unit cell. For instance, the basis for BCC structure is (0 0 0; 1/2 1/2 1/2) and for FCC structure (0 0 0; 1/2 r © 2003 by CRC Press LLC M M d te mperature Temperature below which a strain-induced martensite occurs under the influence of plastic deformation; it is higher than the M s σ temperature. M s σ temperature Temperature below which a stress-assisted martensite occurs; it is higher than M s a nd lower than M d temperature. macrograph Photograph of macrostructure. macroscopic stress Residual stress acting at distances significantly greater than the mean grain size. macrosegregation Heterogeneity revealing itself in different chemical compo - sition and, sometimes, in different phase constituents in various parts of an ingot or casting. Macrosegregation occurs on solidification and is always nonequilibrium. Its formation can be explained in the same way as that of coring, but in the case of macrosegregation, s 1 , s 2 , and s 3 (s ee Figure M.1) show the compositions of different ingot parts. Macrosegre - gation is also referred to as major or zonal segregation or as liquation. FIGURE M.1 Occurrence of macrosegration in alloy X in the course of solidification. Points s 1 , s 2 , and s 3 sh ow compositions of the ingot parts solidified at temperatures T 1 , T 2 , and T 3 , respectively. For further details, see coring, Figure C.3. X X s 1 s 2 s 3 T 1 T 2 T 3 Temperature L + α α β L L A B α A %B © 2003 by CRC Press LLC . Manifestation of the difference in diffusion rates of the atoms of different components in the case of vacancy mechanism, i.e., in substitutional solid solutions. An annealing of a sample made of two. connecting two parallel segments of the same dislocation lying on both sides of the Peierls barrier. Kinks can easily glide along with the dislocation. kink band Part of a plastically deformed grain sample made of two closely contacting parts of different compositions results in the follow - ing. First, the interface between these parts shifts into the part with the higher intrinsic diffusivity