Quenched from

Figure C2.1.9. Specific voiume of poiy (vinyi acetate) as a function of tiie temperature measured during heating two sampies which were preiiminary quenched from tiie meit to -20 °C. One sampie was stored for i min and tiie otiier for iOO h at -20 °C before heating. (Figure from [77], reprinted by pennission of Joim Wiiey and Sons Inc).

Lead—silver alloys show significant age hardening when quenched from elevated temperature. Because of the pronounced hardening which occurs using small amounts of silver, the content of silver as an impurity in pure lead is restricted to less than 0.0025 wt % in most specifications. Small additions of silver to lead produces high resistance to recrystaUization and grain growth. 

Vanadium—Cobalt-Iron Alloys. V—Co—Fe permanent-magnet alloys also are ductile. A common commercial ahoy, Vicahoy I, has a nominal composition 10 wt % V, 52 wt % Co, and 38 wt % Fe (Table 10). Hard magnetic properties are developed by quenching from 1200°C for conversion to bcc a-phase foUowed by aging at 600°C (precipitation of fee y-phase). The resulting properties are isotropic, with ca kJ/m ... 

Fig. 6. (a) The effect of sub2ero cooling on the hardness gradient in a carburized and quenched 3312 steel where (e) is oil quenched from 925 to 20°C and ( ) is cooled to -195°C. The initial quench to 20°C does not convert all of the austenite to martensite because the high carbon content in the surface region lowers the temperature below 20°C. Subsequent cooling to -195°C converts most of the retained austenite to martensite, raising the hardness, (b) The... 

Precipitation Heat Treatment. The supersaturated solution produced by the quench from the solution temperature is unstable, and the alloys tend to approach equiUbrium by precipitation of solute. Because the activation energies required to form equiUbrium precipitate phases are higher than those to form metastable phases, the soHd solution decomposes to form G-P zones at room temperature (natural aging). Metastable precursors to the equihbrium phases are formed at the temperatures employed for commercial precipitation heat treatments (artificial aging). 

Theoretical investigations of quenched-annealed systems have been initiated with success by Madden and Glandt [15,16] these authors have presented exact Mayer cluster expansions of correlation functions for the case when the matrix subsystem is generated by quenching from an equihbrium distribution, as well as for the case of arbitrary distribution of obstacles. However, their integral equations for the correlation functions... 

The relaxation time r of the mean length, = 2A Loo, gives a measure of the microscopic breaking rate k. In Fig. 16 the relaxation of the average length (L) with time after a quench from initial temperature Lq = 1.0 to a series of lower temperatures (those shown on the plot are = 0.35,0.37, and 0.40) is compared to the analytical result, Eq. (24). Despite some statistical fluctuations at late times after the quench it is evident from Fig. 16 that predictions (Eq. (24)) and measurements practically coincide. In the inset is also shown the reverse L-jump from Tq = 0.35 to = 1.00. Clearly, the relaxation in this case is much ( 20 times) faster and is also well reproduced by the non-exponential law, Eq. (24). In the absence of laboratory investigations so far, this appears the only unambiguous confirmation for the nonlinear relaxation of GM after a T-quench. 

FIG. 16 Time evolution of the average length for a living polymer system [59] after a quench from an initial Tq = 1.0 to three final temperatures = 0.35 (circles),... 

Langevin simulations of time-dependent Ginzburg-Landau models have also been performed to study other dynamical aspects of amphiphilic systems [223,224]. An attractive alternative approach is that of the Lattice-Boltzmann models, which take proper account of the hydrodynamics of the system. They have been used recently to study quenches from a disordered phase in a lamellar phase [225,226]. 

Figure 9 Ambient-temperature x-ray diffractograms of PDTMB samples (a) annealed at 70°C for 24 days, and (b) freshly quenched from the melt [25,26]. Noise has been suppressed.

Figure 13 Small-angle synchrotron profiles [30] corresponding to three PTEB samples freshly quenched from the melt (dotted line), annealed at room temperature for 12 months (dashed line), and annealed at 85°C during 12 days (continuous line).

In conclusion, the different thermal histories imposed to PTEB have a minor effect on the /3 and y relaxations, while the a. transition is greatly dependent on the annealing of the samples, being considerably more intense and narrower for the specimen freshly quenched from the melt, which exhibits only a liquid crystalline order. The increase of the storage modulus produced by the aging process confirms the dynamic mechanical results obtained for PDEB [24], a polyester of the same series, as well as the micro-hardness increase [22] (a direct consequence of the modulus rise) with the aging time. 

Figure 5 Free energy surface at l l(Fig. 5a) [22, 24, 28] and 1 3 (Fig. 5b) [23, 24, 33] stoichiometries in the vicinity of disordered state ( f=0.0) at T—. 7Q and 1.6, respectively. The solid line in left-hand (right-hand) figure indicates the kinetic path evolving towards the L q LI2 ordered phase when the system is quenched from T—2.5 (3.0) down to 1.70 (1.60), while the broken lines are devolving towards disordered phase. The open arrows on the contour surface designate the direction of the decrease of free energy, and the arrows on the kinetic path indicate the direction of time evolution or devolution.

Fig. 8. Temporal evolution of q for the alloy model described in text after the quench from T = 0.9 to T = 0.61. at following times t after the quench (a) 0, (b) 120, (c) 260, and (d) 1000.

Comparison of Ordering After Quenching from above T, with Order-Order Relaxations The Influence of Antiphase Domain Growth... 

Figure 7. Resistivity change during isochronal anneaUng of Ni76Al24+0.19at%B ( pure ordering ) after separating non-ordering effects of defect recovery from as-measured curves (broken line) For more details see . S1(G) 8% reduction, S2(0) 14% reduction, S3(i) slow-cooling, S4( ) quenched from 973K.

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