Phase Transformations in Low-Fe Alloys of the Al-Cu-Fe System

Microstructure and phase transformation in the Al-Cu-Fe alloys of the approximate compositional range of 20-50 at.% Cu and 2 - 10 Fe at.% have been investigated from samples quenched from their respective temperatures by means of different thermal analysis, magnetothermal analysis, scanning electron microscopy, electron probe analysis and powder X-ray diffraction. Representative phase transformations categorized as polymorphic, discontinuous precipitation,quasi-binary eutectoid, and ternary transitional U-type phase transformation are presented. These phase transformations were found to have a common feature which consumes the β phase and appears the φ phase. A schematic diagram was proposed to demonstrate the transition processes with decreasing temperature.     

Phase Transformations in High-Temperature Alloys of the Ni – Cr – Fe – Nb System

Metal Science and Heat Treatment -     

Copper-Indium Alloy Transformations

Phase transformations of copper-indium alloy thin films are analyzed by hot-stage x-ray diffraction (XRD) over the temperature range from 30 to 425 °C in controlled ambient. Thin films of Cu/In with a molar ratio of approximately 0.9 were used. In situ experiments were carried out in a reducing hydrogen atmosphere to minimize oxide formation. The as-deposited Cu/In alloy transformed at 150 °C to form Cu₁₁In₉. Ramping the temperature to the upper limit of 425 °C revealed an additional transformation at 350 °C to form Cu₁₆In₉.     

Copper-Indium Alloy Transformations

Phase transformations of copper-indium alloy thin films are analyzed by hot-stage x-ray diffraction (XRD) over the temperature range from 30 to 425 °C in controlled ambient. Thin films of Cu/In with a molar ratio of approximately 0.9 were used. In situ experiments were carried out in a reducing hydrogen atmosphere to minimize oxide formation. The as-deposited Cu/In alloy transformed at 150 °C to form Cu₁₁In₉. Ramping the temperature to the upper limit of 425 °C revealed an additional transformation at 350 °C to form Cu₁₆In₉. (DuPont Company Contribution Number: 7722).     

应力作用下的相变

水静压抑制Fe-C和钢中体积膨胀型相变，如铁素体、珠光体、贝氏体和马氏体相变。单向应力促发铁素体和珠光体相变，拉应力的效果尤为显著。0．38C-Cr-Mo钢中，铁素体、珠光体和贝氏体相变在应力下的动力学，可由Johnson-Mehl-Avrami方程中加入应力因子经修正来描述。由于铁素体和珠光体的化学驱动力小，应力所作膨胀功使形核率(J^*)增高和孕育期τ缩短。而贝氏体相变中，可能由于应力下碳自奥氏体贫化，或减少相界面能，从而使τ增高和τ缩短，待试验予以证明。水静压对Ms温度影响的定量描述因不同材料而异。列出Patel-Cohen所建立的dMs／dσ方程，及本文作者提出的应力影响Ms的方程。应力诱发马氏体会改变其晶体学及形态，提出以形核率的数值来判定其形态。奥氏体的力学稳定化在马氏体相变中主要由于奥氏体强化所导致，在贝氏体相变中却主要由于晶体学阻碍长大所造成的。     

New Concepts of the Nature of Bainitic Transformations in Steels

Special features of theγ → transformation occurring in a wide range of cooling rates (0.1 – 500,000 K/sec) in pure iron and in carbon and chromium steels are considered. It is shown that four stages of the γ → transformation are possible in the steels, the first of which has a diffusion or massive nature, and the other three can be characterized as displacement transformations. The genetic tie between the upper and lower bainite and transformations occurring through stages II and III, respectively, in pure iron is shown. The difference between the upper and lower bainite is determined by the difference in the mechanisms of motion of the phase boundary, which can be accompanied by redistribution of carbon atoms. Stage IV corresponds to athermal martensitic transformation. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 24 – 29, July, 2005.     

Transformations in cementite in the zone of contact with ferrous phases

Conclusions When cast irons containing ledeburitic cementite are heated, the peripheral regions of the inclusions are decarburized as a result of the diffusion of carbon to the surrounding metal, and the chemical composition of the carbide M₃C deviates from stoichiometric. This is manifested by the formation of microrelief on the surface of the inclusion of ledeburitic cementite, in which the layered structure within a single monocrystal of cementite has practically a single preferred direction. The development of microrelief and the formation of baikovite have much in common.Vinnitsk Polytechnic Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 2–3, December, 1992.     

Phase Transformations in Tempering of Roll Steels

Phase transformations in roll steels 8Kh2SGF and 6Kh5M1FS with different stability of supercooled and retained austenite are studied in the processes of quenching cooling and low-temperature tempering with long-term isothermal holds.__________Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 12 – 14, January, 2005.     

Transformations [in steel] during heating

Conclusions It was shown by various experimental methods that higher grain refinement temperature and the disappearance of texture during a secondary accelerated heating of previously quench-hardened steels are associated not with the recrystallization of strain-hardened austenite, but with the normal phase recrystallization which is determined by two basic factors: the alloy content of thea-phase and the heating rate.     

Structural and Phase Transformations in Titanium Alloys

Metal Science and Heat Treatment -     

Phase Transformations in Cast Superaustenitic Stainless Steels

The goal of this investigation was to study phase transformations in cast superaustenitic stainless steels. Experiments were performed to determine the phase transformation behavior for alloys CN3MN and CK3MCuN. Samples were taken from keel bars that were heat treated between 1160 and 1230 °C and then isothermally held for times ranging from 1 min to 2040 h at temperatures in the range of 700-900 °C. The resulting microstructures were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy and wavelength dispersive spectroscopy. The microstructures, composed primarily of sigma- and Laves-phases within a purely austenitic matrix, showed relatively slow transformation kinetics, with transformation not completed even after the longest anneals. SEM and TEM analysis of superaustenitic samples reveal that precipitation takes place initially on grain boundaries and proceeds intragranularly. The results of these SEM and TEM investigations, along with volume fractions and number densities as a function of time and temperature, will be presented and discussed.     

Syntactic Transformations on Distributed Representations

There has been much interest in the possibility of connectionist models whose representations can be endowed with compositional structure, and a variety of such models have been proposed. These models typically use distributed representations that arise from the functional composition of constituent parts. Functional composition and decomposition alone, however, yield only an implementation of classical symbolic theories. This paper explores the possibility of moving beyond implementation by exploiting holistic structure-sensitive operations on distributed representations. An experiment is performed using Pollack's Recursive Auto-Associative Memory (RAAM). RAAM is used to construct distributed representations of syntactically structured sentences. A feed-forward network is then trained to operate directly on these representations, modeling syntactic transformations of the represented sentences. Successful training and generalization is obtained, demonstrating that the implicit structure present in these representations can be used for a kind of structure-sensitive processing unique to the connectionist domain.