Thermomechanical treatment

Because of constitutional complexity, the exact chemistries of nickel-base superalloys must be controlled carehiUy in order to avoid the precipitation of deleterious topologically close-packed (TCP) phases and extraneous carbides after long-term high temperature exposure. Heat-treatment schedules and thermomechanical treatments in the case of wrought alloys also are important to provide optimum strength and performance. 

The late discovery of acetyl xylan and feruloyl esterases has been partly due to the lack of suitable substrates. Xylans are often isolated by alkaline extraction, in which ester groups are saponified. Treatment of plant materials under mildly acidic conditions, as in steaming or aqueous-phase thermomechanical treatment, leaves most of the ester groups intact. These methods, however, partly hydrolyze xylan to shorter fragments (63,69). Polymeric acetylated xylan can be isolated from delignified materials by dimethyl sulfoxide extraction (70). The choice of substrate is especially important in studies of esterases for deacetylation of xylans. The use of small chromophoric substrates (p-nitrophenyl acetate, a-naphthyl acetate, and methylumbelliferyl acetate) analogously to the assays of disaccharidases may lead to the monitoring of esterases unable to deacetylate xylan (33, 63, 64). 

Ti-6A1-4V is probably the most widely used Ti alloy in the world. It is an alloy with a duplex structure containing solid solutions based on the a, c.p.h. A3 and / , b.c.c. A2 allotropes of Ti. In its final heat-treated form it consists predominantly of a and its high strength is partly derived from its final microstructure which is manipulated by a series of thermomechanical treatments that include hot isothermal forging just below its P transits temperature (T ). The interest is, in the first place, to predict and how the amounts of a and P vary with temperature. 

The capillary forces have been recognized as intermolecular forces which are created by cohesion and adhesion at interfaces. From the evaluation of the thermomechanical treatment we could clearly make out that these forces depend on the free Helmholz energy functions of the solid phase and the density gradient of the liquid. 

Al-Sc alloys in consequence of high recrystallization temperature are the best materials for creation of the superplastic state. Al - Mg - Sc alloys are used as the superplastic materials the most frequently [9-13], These alloys are natural superplastic materials, since they are superplastic after standard thermomechanical treatment, for example after cold rolling and following annealing. Elongation to fracture in Al - Mg - Sc alloys maybe up to 1000 % and parameter m that characterizes the sensibility of yield stress to the deformation rate maybe m = 0.6 -h 0.7. 

EFFECT OF THERMOMECHANICAL TREATMENT ON STRUCTURE AND PROPERTIES OF TI-B-X ALLOYS... 

Effect of thermomechanical treatment on structure and properties of 255 Ti-B-X alloys... 

Some examples of applications of neutron and synchrotron radiation diffraction applied to the determination of residual stresses in various industrial and technological components have been presented. The reliability of the technique has been shown, being able to determine residual stresses induced by various thermomechanical treatments, such as shrink-fit joints, welds and surface treatments in automotive and aerospace materials. It has been shown how, by this method, it is possible to determine stresses both in the coating and in the substrate of plasma-spray deposed hydroxyapatite layers on Ti alloy for biomedical applications. 

Poly(ethylene terephthalate) Poly(ethylene terephthalate) is a widely used semicrystalline polymer. The macroscopic properties of PET such as thermal, mechanical, optical, and permeation properties depend on its specific internal morphologies and microstructure arrangement. It can be quenched into the completely amorphous state, whereas thermal and thermomechanical treatments lead to partially crystallized samples with easily controlled degrees of crystallinity. The crystallization behavior of thermoplastic polymers is strongly affected by processing conditions [91-93]. 

Using new methods (7) for following the transformation of metal soaps in the polymer, this chapter studys the synergism obtained from chloride ions between zinc and calcium stearate in the absence or presence of secondary stabilizers during PVC thermomechanical treatments in the Brabender plasticorder or in a rolling mill. 

The mechanical behaviour is improved by reduction of A1 content, alloying with further elements and thermomechanical treatments, which leads to alloys for eventual applications in conventional power plants - in particular in steam turbines - or in coal conversion plants. Exhaust units in cars and electric heating elements are near application. 

Since the transition metal elements in these ternary Laves phases can substitute for each other freely, and since the distribution of Laves phase can be controlled by thermomechanical treatments there are possibilities for optimizing such NiAl alloys with Laves phases with respect to creep resistance and the brittle-to-ductile transition temperature (BDTT) by controlling the composition and phase distribution, and this is being studied presently... 

The Cu-Al-Ni alloys are advantageous because of their higher stability at higher temperatures compared with the Cu-Zn-Al alloys. However, second-phase precipitation cannot be suppressed and embrittles the Cu-Al-Ni alloys and precludes cold working, i.e. such alloys can only be hot finished (Van Humbeek and Delaey, 1989 Hodgson, 1990). Thermomechanical treatments and microalloying additions - in particular Mn, Ti, and Zr - are used for... 

In this chapter, the FSW process parameters that can affect microstructure/property distributions in aluminum alloy friction stir welds are described. The chapter includes a brief description of the main classes of aluminum alloys, the processing routes (thermomechanical treatments) typically associated with each class, and how FSW parameters can be manipulated, in a general way, to modify the microstructure and... 

PLA is a rigid polymer at ambient temperature (see Table 9.1). It crystalhzes slowly, like PET. The ciystalhzation kinetics of PLA has been extensively studied. Like PET, PLA can be oriented by thermomechanical treatment. Orienting the chains notably increases its mechanical strength. 

Thermomechanical treatment showed superior corrosion resistance on AA5083 corrosion compared to as-received samples. Precipitates such as Al-(Fe, Si, Mn, Cr), Al-13Fe4, Al6(Fe, Mn), and Mg2Si together with the P-phase post-sensitization were identified using SEM, EDS, and TEM. Dislocation networks showed better corrosion resistance than the matrix [47]. 

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