Entity

Time filter

Source Type

Nogent-sur-Oise, France

Martinez R.,Laval University | Larouche D.,Laval University | Cailletaud G.,MINES ParisTech Center of materials | Guillot I.,CNRS East Paris Institute of Chemistry and Materials Science | Massinon D.,Montupet SA
Modelling and Simulation in Materials Science and Engineering | Year: 2015

The precipitation of Al2Cu particles in a 319 T7 aluminum alloy has been modeled. A theoretical approach enables the concomitant computation of nucleation, growth and coarsening. The framework is based on an implicit scheme using the finite differences. The equationof continuity is discretized in time and space in order to obtain a matricial form. The inversion of a tridiagonal matrix gives way to determining the evolution of the size distribution of Al2Cu particles at t +Δt. The fluxes of in-between the boundaries are computed in order to respect the conservation of the mass of the system, as well as the fluxes at the boundaries. The essential results of the model are compared to TEM measurements. Simulations provide quantitative features on the impact of the cooling rate on the size distribution of particles. They also provide results in agreement with the TEM measurements. This kind of multiscale approach allows new perspectives to be examined in the process of designing highly loaded components such as cylinder heads. It enables a more precise prediction of the microstructure and its evolution as a function of continuous cooling rates. © 2015 IOP Publishing Ltd. Source


Chaudhury S.K.,Ahmedabad University | Apelian D.,Worcester Polytechnic Institute | Meyer P.,Aleris | Meyer P.,Montupet SA | And 2 more authors.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2015

Microstructure and mechanical properties of B319 alloy diesel cylinder heads were investigated in this study. Cylinder heads were heat treated to T5, T6, and T7 tempers using fluidized bed technology. Three different fluidized beds were used, each to solutionize, quench, and age the castings. For comparative purposes, castings were also aged using conventional forced-air circulation electric-resistance furnace. Effects of processing parameters such as temperature, time, and heating rate on microstructural evolution and mechanical properties namely tensile properties and hardness of B319 alloy castings were studied. The number density and size range of precipitates were measured. Results show that the T5 temper has no effect on eutectic phases such as Si- and Fe-rich intermetallic, and Al2Cu. On contrary, both T6 and T7 tempers result in spherodization of the eutectic Si and partial dissolution of the Al2Cu phase. Prolonged solution heat treatment for 8 hours in fluidized bed results in limited dissolution of the secondary eutectic Al2Cu phase. Aging (T6, T7, and T5) results in precipitation of Al5Cu2Mg8Si6 and Al2Cu phases in B319 alloy. The number density of precipitates in T6 temper is greater than in T7 and T5 tempers. The number density of precipitates is also affected by the duration of solution heat treatment. In general, long solution heat treatment (8 hours) results in greater precipitate density than short solution treatment (2 hours). The distribution of precipitates is inhomogeneous and varied across the dendritic structure. In general, precipitation rate of Al5Cu2Mg8Si6 phase is greater near the periphery of the dendrite as compared to the center. This is because Al5Cu2Mg8Si6 nucleates on Si particle, grain boundaries, and triple junction between recrystallized Al grains and Si particles. Similarly, heterogeneous sites such as grain boundaries and Al/Si interface also act as nucleating sites for the precipitation of Al2Cu phase. In general, the coarsening rate of precipitates near to the periphery of the dendrite is greater than in the center. This is because the Al matrix region close to the eutectic Si particles is subjected to in situ thermal stresses, which is generated due to the thermal mismatch between Al and Si particles. Thermal stress is highest at the Si/Al interface and decreases significantly away from the Al/Si interface. The precipitation and growth rate of the alloy aged in fluidized bed is greater than in conventional furnace. This is because heating rates of casting in fluidized bed (FB) are greater than conventional furnace, which result in greater precipitation rate. This study establishes a correlation between structure, thermal processing, and property of B319 alloy treated to various heat treatments. Reasonably good mechanical properties were obtained in less time using fluidized bed furnace. This work clearly demonstrates the significant potential of FB to save time and energy. © 2015, The Minerals, Metals & Materials Society and ASM International. Source


Chaudhury S.K.,Worcester Polytechnic Institute | Chaudhury S.K.,Ahmedabad University | Apelian D.,Worcester Polytechnic Institute | Meyer P.,Montupet SA | And 2 more authors.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2015

Effects of various heat treatment tempers on fatigue performance of 319 alloy diesel cylinder heads were investigated. Castings were heat treated to T5, T6, and T7 tempers. Castings were solution heat treated and quenched using fluidized beds and aged using both conventional air convective furnace and fluidized bed for T6 and T7 tempers; while they were aged after casting for T5 temper using conventional furnace. Fatigue tests were performed at 373 K (100 °C) and stress ratio equal to −1. Results show that heat treatment has significant effect on the fatigue behavior of 319 alloy. The fatigue strength of T6 tempered 319 alloy is greater than T5 and T7 treatments. Weibull analysis shows that the Weibull modulus and characteristic fatigue life of castings treated (using conventional forced air circulation electrical resistance furnace) to T6 and T7 tempers are greater than T5 temper. This implies that castings treated to T6 and T7 tempers have greater reliability vis-à-vis T5 temper. Fractographic analyses reveal three distinct regions. These are: (I) crack initiation region from the surface, (II) crack propagation region, and (III) catastrophic or monotonic failure region. The relative size of the crack propagation region in T6 and T7 treated samples is greater than T5 treated samples. In general, the monotonic failure region shows typical dimple morphology, which implies significant plastic deformation prior to failure. Dimples on the fractured surface of T5 treated alloy are relatively more faceted than those treated to T6 and T7 tempers. This implies that the 319 alloy treated to T6 and T7 tempers underwent higher degree of plasticity prior to failure than that in the T5 condition. © 2015, The Minerals, Metals & Materials Society and ASM International. Source


Jia Z.-H.,Chongqing University | Jia Z.-H.,Norwegian University of Science and Technology | Couzinie J.-P.,CNRS East Paris Institute of Chemistry and Materials Science | Cherdoudi N.,CNRS East Paris Institute of Chemistry and Materials Science | And 9 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

The precipitation behaviours of Al 3Zr precipitate in the Al-Cu-Zr and Al-Cu-Zr-Ti-V alloys were studied by transmission electron microscopy. Metastable Al 3Zr precipitates are homogeneously nucleated in dendrite centres resulting in homogeneous distribution. However, the precipitation in the interdendritic regions is complex and the precipitation morphologies, helical-like and stripe-like shapes, were observed, which are composed of many spherical Al 3Zr precipitates. The stripe-like precipitate clusters have preferential orientations along with the -100- Al directions, which is inferred to be related to θ'(Al 2Cu) and θ phases. Addition of Cu can accelerate the L1 2→D0 23 structural transformation of the Al 3Zr precipitate. Source


Jomaa G.,MINES ParisTech | Jomaa G.,Montupet SA | Goblet P.,MINES ParisTech | Coquelet C.,MINES ParisTech | Morlot V.,Montupet SA
Thermochimica Acta | Year: 2015

The pyrolysis of polyurethane was studied by dynamic thermogravimetry analysis (TGA). The studied polyurethane is used as organic binder in casting process to make sand cores and molds. A semi-empirical model is presented that can be used to describe polyurethane pyrolysis occurring during TGA experiments. This model assumes that the polyurethane is pyrolysed by several parallel independent reactions. The kinetic parameters of polyurethane pyrolysis were evaluated by fitting the model to the experimental data obtained by TGA over a wide variety of heating rates. A nonlinear least-squares optimization method is employed in the fitting procedure. A hybrid objectives based simultaneously on the mass (TG) and mass loss rate (DTG) curves has been used in the least-squares method. The values of the activation energy obtained by the non-linear fitting were then recalculated by the methods of Kissinger and Friedmand. Furthermore, the parameters obtained in the present paper were then compared with those reported in the literature. © 2015 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations