A mathematical model for calculating phase transformations in steels during rapid heating and cooling is presented. It is based on a rule of additivity. The isothermal kinetics are modelled by Johnson-Mehl-Avrami law. The model des6ribes the kinetics of austenitization during heating. the state of austenite at the end of heating (carbon content, grain size), the kinetics of transformations during cooling. the final microstructure and hardness. The model is worked out firstly on dilatometric specimenswithout thermal gradients in order to validate the modelling and the input data. Thenthe application of the model to massive cylinders heated up and cooled down with high thermal gradients is presented. Introduction In the past a number of studies have dealt with the prediction of microstructural evolutions of steels during cooling. A review has been given inl'2) to which some other works should be added.3,4) Only a few studies concern the calculation of the kinetics of austenitization during rapid heating.4'5) Moreover the modelling of the effect of the state of austenite at the end of heating (inhomogeneouschemical composition, grain size) on the kinetics of phase transformations during cooling has been little taken up. Several authors4'6,7) have introduced the grain size of austenite as a parameter in the laws describing the isothermal or anisothermal kinetics of transformation. As far as we know only one study8) takes into account the effect of local carbon content of austenite on the critical cooling rate and on Mstem-perature. Someyears ago, we have developed a model for calculating phase transformations during continuous cooling in steels.1'2) In this paper we present an extension of this model in order to describe also phase transformations during heating. An approach for taking into account both the effect of the local carbon content of austenite and the effect of the grain size of austenite on the kinetics of phase transformations during cooling is presented. The model is worked out firstly on dilatometrlc specimens without thermal gradients for which the parameters needed for the validation of the computations are measured. Then we illustrate how the modelworks on cylindrical specimens with high thermal gradients. Finally, an application of the model to induction hardening is r.c) 1992 ISIJ 31 6 shown. 2. The methodused in this paper for calculating phase transformations during continuous heating from iso-thermal data is based on a rule of additivity. It has been used by several authors2,5,9) and we recall briefly the principal of the method. The temprature-time curve is discretized in a series of isothermal steps. On each step the volume fraction of new phase formed is calculated by using isothermal transformation kinetics. The iso-thermal transformation kinetics is modelled according to the law developed by JohnsonMehllo) and by Avrami I i): yk = y~** k(I-ex p(-bkt"k)) where yk is the volume fraction of constituent k transformed into austenite (k= I Pearlite, k=2 ferrite) and bk and nk are temperature de...

Carbon nanotube reinforced alumina matrix nanocomposite was fabricated by cold spray process on Al-Si alloys surfaces. The effects of various amounts of CNTs from 0, 2 and 4 wt % on alumina powders were investigated. Results show that the improvement in both wear resistance and hardness was provided by 2 wt. % CNTs reinforcement. The hardness of carbon nanotube reinforced alumina matrix nanocomposite was increased due to an enhanced load sharing of homogeneously distributed carbon nanotubes. Homogeneous distribution of CNTs within the Al 2 O 3 matrix and strong interfacial connection between CNTs-Al 2 O 3 give nanocomposites with superior wear properties.

Graft copolymer of Amylopectin and PMMA was synthesized by atom transfer radical polymerization (ATRP) method. The hydroxyl groups of amylopectin partially substituted with tert-butyl a-bromoisobutyrate to form tert-butyl a-bromoisobutyrate (TBBiB ) groups. This compound is known as an efficient macro-initiator for ATRP process. This research, aimed to obtain a bio based polymer of Amylopectin, in which the amylopectin was used as macro-initiator in the ATRP of MMA. The experiment was carried out in the homogeneous system under temperature range of 40 – 70°C in DMSO solution using TEA as catalyst. The modified amylopectin-TBBiB then was grafted to methyl methacrylate trough ATRP. Product characterization indicates that the graft copolymer Amylopectin-g-PMMA is efficient and the obtained product owns well defined structures

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Reliability of equipment of the oil and gas industry is vital, whereas on pipeline transmission system, decreasing the integrity of the pipeline is generally caused by corrosion. Failure that occurs due to corrosion deterioration influenced by the environment within a certain time, and has exceeded the nominal thickness of the pipe so there is a failure. This study used the reliability analysis approach based on modeling corrosion degradation ratio that is determined by the amount of the corrosion rate externally and internally. Using the Weibull probabilistic distribution method, results that the reliability of pipeline will decrease with increasing lifetime. It was identified that internal corrosion has a major contribution to the remaining life of pipeline. From the calculation results obtained by external corrosion has the greatest reliability over 60 years, followed by internal corrosion less than 30 years and the least is by cumulative corrosion which is less than 20 years. From the value of reliability, it can be known probability of failure (POF) which is the anti reliability.