[Elenco soci]


Zago Marco

Ricercatore TD(B)


Università degli Studi di Trento
marco.zago-1@unitn.it

Sito istituzionale
SCOPUS ID: 56276408900



Pubblicazioni scientifiche

[1] Zago M., Perina M., Cristofolini I., Preliminary Design Method Accounting for Shape Distortion in Metal Binder Jetting Parts: A Case Study, Lecture Notes in Mechanical Engineering, 925-936, (2023). Abstract
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Abstract: Additive Manufacturing (AM) technologies theoretically allow the production of complex products without any geometrical restriction. Nevertheless, production process delineates some limitations on the resulting dimensional and geometrical precision. This is a critical issue mainly for Metal Binder Jetting (MBJ) process, on the reason of anisotropic dimensional change and distortion on sintering. Literature reports fairly reliable models for predicting the deformation on sintering. However, the application of such methods might be time consuming from industrial perspective, because of the extensive experimental analysis required to assemble a robust material database. For that reason, this work aims at proposing an alternative approach for compensating dimensional and geometrical change on sintering. Two complex geometries, having similar geometrical features with different sizes, were printed and measured by a coordinate measuring machine before and after sintering process. The analysis of cylindricity form errors reveals an excellent geometrical stability of smaller geometry. Therefore, dimensional change along printing direction was derived in order to obtain a precise scaling factor for improving the dimensional and geometrical precision. By contrast, bigger samples encountered a dramatic distortion, which required a complete redesign. The shape of the distorted cylinder was approximated with an ellipse and a corrective function has been proposed for compensating green geometry.

Keywords: Additive manufacturing | Binder jetting | Design for AM | Distortion

[2] Zago M., Lecis N.F.M., Vedani M., Cristofolini I., Geometrical Issues in Design for Binder Jetting – The Effect of Anisotropic Dimensional Change on Sintering, Lecture Notes in Mechanical Engineering, 410-421, (2022). Abstract
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Abstract: Recent research has been focused on the binder jetting (BJ) additive manufacturing technique due to the high potential possibilities in industrial applications. The actual limitation of BJ process can be attributed to the difficult control of the product quality. In fact, a high dimensional variation occurs on sintering, which can detrimentally affect dimensional and geometrical precision, when not properly considered in the design step. This paper aims at investigating the influence of sintering on the dimensional change of through holes, with different diameter size and different axis orientation with respect to the building direction. Samples were measured in the green and sintered state by means of a coordinate measuring machine in order to calculate the diameter shrinkage. The empirical data were successfully compared with the prevision of an analytical model demonstrating that diameter shrinkage is influenced by: the anisotropic dimensional change, the axis orientation and the position of the two diametral opposite points used to identify the diameter. A deep analysis of the results showed a non-negligible effect of the gravity-induced load and of the inhomogeneous shrinkage on sample geometry. This study highlighted that the analytical model may serve as a basis in the design step for improving the dimensional quality of BJ product.

Keywords: Binder jetting | Design for additive manufacturing | Dimensional and geometrical precision

[3] Cristofolini I., Molinari A., Zago M., Uçak O.U., Vicenzi B., Dougan M.J., Schneider M., Pedersen P.H., Bolitschek J., Voglhuber J., Development of a new model describing the anisotropic dimensional change on sintering, Powder Metallurgy, 65(2), 89-100, (2022). Abstract
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Abstract: The anisotropic dimensional changes during sintering were investigated for rings made of eight different materials with different green densities and H/(Dext −Dint) ratio. Dimensional changes are affected by green density, as shown in previous works, while the geometrical parameter does not display a clear influence. The anisotropy parameter K defined in a previous work does not describe anisotropy of dimensional change unambiguously, due to the anisotropy of shrinkage/swelling in the compaction plane. A new anisotropy parameter (K 3D) was therefore defined considering the dimensional changes of internal diameter, external diameter and height. This parameter displays an unambiguous dependence on the equivalent isotropic dimensional change and will be used in further work to develop a predictive model for the prediction of the anisotropic dimensional change during sintering of parts with different green densities and geometry.

Keywords: anisotropy | Dimensional change

[4] du Plessis A., Schwaderer G., Cristofolini I., Zago M., Benedetti M., Dimensional metrology of additively manufactured lattice structures by combined tactile probe and X-ray tomography, Material Design and Processing Communications, 3(6), (2021). Abstract
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Abstract: Additive manufacturing allows high complexity of manufactured structures, permitting entirely new design capabilities. In the context of complex design, lattice structures hold the most promise for high complexity, tailorable and ultra-lightweight structures. These unique structures are suitable for various applications including light-weighting, energy absorption, vibration isolation, thermal management amongst many others. This new complexity leads to new manufacturing quality control and metrology challenges. Traditional metrology tools cannot access the entire structure, and the only reliable method to inspect the inner details of these structures is by X-ray computed tomography (CT). This work highlights the challenges of this process, demonstrating a novel workflow for dimensional metrology of coupon lattice samples—using a combination of surface and internal metrology using tactile probe and CT. This dual combined approach uses traditional surface coordinate measurement on exterior accessible surfaces, which is followed by internal lattice measurements. The results show a clear method and workflow for combining these technologies for a holistic dimensional inspection. The confidence gained by inspection of such lattice coupons will support the application of these lattices in end-use parts.

Keywords: calibration | laser powder bed fusion | lattice structures | metal additive manufacturing | metrology | X-ray tomography

[5] Zago M., Lecis N.F.M., Vedani M., Cristofolini I., Dimensional and geometrical precision of parts produced by binder jetting process as affected by the anisotropic shrinkage on sintering, Additive Manufacturing, 43, (2021). Abstract
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Abstract: Dimensional and geometrical precision of parts produced by binder jetting is a crucial issue to be considered aiming at promoting the transition to industrial production. The influence of both the printing and the sintering processes has to be evaluated, and the high shrinkage has to be considered. The task is further complicated by the anisotropy of dimensional change on sintering. The aim of this work is to investigate the dimensional and geometrical precision of cylindrical holes, as affected by the anisotropy of dimensional change on sintering after binder jetting. AISI 316 L powder was used to produce five different geometries, characterized by four holes with different orientation with respect to the printing direction. The geometrical features were measured both in the green and in the sintered state with a coordinate measuring machine, and the dimensional changes, as well as the geometrical variations, were calculated. According to the author's previous experience, a theoretical model has been defined, which aims at predicting the geometry of the holes as derived by the anisotropic dimensional change on sintering. The expected dimensional change of hole diameters, the variation of cylindricity, and the variation of the axis inclination were calculated by the model and compared to those derived from measurement. Good agreement between predicted and measured results has been observed, providing that the influence of printing process parameters is considered.

Keywords: Binder jetting | Dimensional and geometrical precision | Metal additive manufacturing | Shrinkage on sintering

[6] Zago M., Cristofolini I., Amirabdollahian S., Designing Powder Metallurgy Process - The Influence of High Sintering Temperature on Dimensional and Geometrical Precision, Lecture Notes in Mechanical Engineering, 3-8, (2021). Abstract
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Abstract: The precision of parts produced by Powder Metallurgy (PM) strongly depends on the careful design of PM process parameters. Among them, high sintering temperature is generally considered as detrimental for dimensional and geometrical precision, and therefore neglected in industrial production. Nevertheless, high sintering temperature would strongly improve mechanical characteristics of PM parts, so that the real influence of high sintering temperature on dimensional and geometrical precision is of great interest for PM companies. This study investigates the influence of sintering temperature (up to 1350 °C) on dimensional and geometrical precision of real parts. Dimensional changes on sintering and the effect of sintering temperature have been evaluated. Geometrical characteristics have been measured both in the green and in the sintered state, and the real influence of sintering temperature has been highlighted. As a conclusion, it has been demonstrated that the larger shrinkage due to the high sintering temperature is not detrimental with respect to the dimensional precision, being it reliably predictable. Moreover, the influence on geometrical characteristics is unexpectedly low. The encouraging results of this study convinced the main PM companies in Europe to further investigate the influence of high sintering temperature, as partners in a Club Project within the European Powder Metallurgy Association (EPMA).

Keywords: Design for powder metallurgy | Dimensional and geometrical precision | High temperature sintering process | Precision engineering | Product development

[7] Cristofolini I., Zago M., Rambelli A., Della Ricca F., The Influence of Lubricant Type and Amount on Warm Die Compaction Mechanics Relationships, Proceedings - Euro PM2020 Congress and Exhibition, (2020). Abstract
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Abstract: The mechanics relationships describing powder behaviour in uniaxial cold compaction have been derived in previous work on the basis of experimental data, as affected by many different variables in the compaction process. The influence of geometry, chemical composition, compaction strategy etc. were investigated in depth. This work focuses on warm die compaction, which stands for an interesting opportunity to increase density, also obtaining more homogeneous density distribution. Cylindrical specimens have been produced using a commercial diffusion bonded low alloy steel powder, to which different lubricants, in different amounts, have been added. The influence of type and amount of lubricant has been directly highlighted by the comparison of ejection force and energy. Axial and radial spring-back have been also evaluated. A deeper knowledge of the behaviour of the different powder mixes in warm die compaction has been obtained comparing the derived friction coefficients and constitutive models.

Keywords: Compaction mechanics | Constitutive models | Ejection | Warm die compaction

[8] Cristofolini I., Zago M., Rambelli A., della Ricca F., Warm die compaction of low alloy steel powder mix – Compaction mechanics and densification, Powder Metallurgy and Particulate Materials - 2021: Proceedings of the 2021 International Conference on Powder Metallurgy and Particulate Materials, PowderMet 2021, 72-81, (2020). Abstract
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Abstract: Powder behavior in uniaxial cold compaction has been extensively investigated in previous work. The constitutive model of different powder mixes has been derived, and the influence of several variables, such as geometry, chemical composition, lubricant type and amount etc., has been studied in depth. This work focuses on the influence of warm die compaction. A commercial diffusion bonded low alloy steel powder, added with 0.6% wt. lubricant, has been used producing cylindrical specimens with two different H/D ratios, both in cold and in warm die compaction. Concerning warm die compaction, two different lubricants have been added. The constitutive model and the densification curves have been derived for all the powder mixes using the data recorded by the press, in terms of forces and displacements. Comparing ejection force and energy, the influence of warm die compaction, type of lubricant, and height of the specimens have been highlighted.

[9] Zago M., Larsson M., Cristofolini I., An Improved Design Method for Net-Shape Manufacturing in Powder Metallurgy, Lecture Notes in Mechanical Engineering, 257-267, (2020). Abstract
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Abstract: The effectiveness of powder metallurgy as net-shape/near net-shape manufacturing technology is determined by the possibility of obtaining complex parts matching the required narrow tolerances. Sintering process determines change in volume of the green, and the related dimensional changes are significantly anisotropic. Anisotropy is affected by several variables, such as material, compaction and sintering parameters, geometry, whose influence is difficult to be distinguished and determined. Anisotropic dimensional change on sintering has been investigated in depth using an experimental approach, relating measurements results to the mechanisms responsible for the phenomenon. Main results concerning the influence of different variables are briefly presented in this work. Such results served as the basis for the development and further improvement of a design method, aimed at predicting anisotropic dimensional change. Main steps of the design method are presented and an example of application to a real part is described. Strong agreement between predicted and real dimensional changes has been observed, and compared to the attainable dimensional tolerances.

Keywords: Design for powder metallurgy | Precision engineering | Product development

[10] Cristofolini I., Molinari A., Zago M., Amirabdollahian S., Coube O., Dougan M.J., Larsson M., Schneider M., Valler P., Voglhuber J., Wimbert L., Design for Powder Metallurgy: Predicting Anisotropic Dimensional Change on Sintering of Real Parts, International Journal of Precision Engineering and Manufacturing, 20(4), 619-630, (2019). Abstract
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Abstract: Anisotropic dimensional change on sintering may strongly affect the precision of parts produced by press and sinter. In previous work a design procedure accounting for anisotropic dimensional change of axi-symmetric parts (disks and rings) has been developed on the basis of experimental data. In this work the procedure has been applied to predict the anisotropic dimensional change of real parts produced in industrial conditions, providing that coaxial rings were identified in the geometry of the actual parts. Parts were highly different for material, complexity of geometry, green density and process conditions. Parts were measured in the green and sintered state and the measured dimensional changes were compared to the predicted ones, finding a good agreement. The procedure was also adapted to predict dimensional change of an oval feature, and highly satisfactory results were obtained.

Keywords: Anisotropy | Dimensional change | Powder metallurgy | Precision of PM parts

[11] Zago M., Cristofolini I., Molinari A., New interpretation for the origin of the anisotropic sintering shrinkage of AISI 316L rings based on the anisotropic stress field occurred on uniaxial cold compaction, Powder Metallurgy, 62(2), 115-123, (2019). Abstract
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Abstract: AISI 316L powder mix was sieved in three particle sizes and successively compacted on rings with two different H/(D ext -D int ) ratios. The height and diameters were measured by a CMM at the green and at the sintered state. The shrinkage was calculated to study the influence of particle size and geometry on the anisotropy of dimensional change. As expected, the volumetric shrinkage increases moving from coarser to finer particle size, and the measurements confirmed the anisotropy of the dimensional variation. The measurements revealed that the lowest rings shrink more than the taller rings. The reference to the radial and axial stress during prior cold compaction shows an interesting correlation, in which shrinkage increases on increasing the stress. The further investigation of the deviatoric stress and the deviatoric shrinkage provided a possible explanation of the anisotropy of dimensional change on sintering as a function of the inhomogeneity of the compaction stress.

Keywords: anisotropic shrinkage | compaction stresses | Sintered steels

[12] Zago M., Cristofolini I., Molinari A., Pederzini G., Rambelli A., Study of elasto-plastic transition as affected by particle size during uniaxial cold compaction, Euro PM 2019 Congress and Exhibition, (2019). Abstract
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Abstract: Compaction mechanics relationships describing the behaviour of AISI 316L powder mixes during uniaxial cold compaction were derived in previous work by continuously recording the data of an industrial press. The reliability of the relationships depends on the accuracy in identifying the threshold of elasto-plastic transition, what is a difficult task due to the peculiar characteristics of powder mixes. The influence of particle size on the transition threshold has been investigated in the present work. Standard commercial AISI 316L powder was sieved in three particle sizes (fine - intermediate - coarse), 1% Acrawax was added as a lubricant and ring-shaped parts were produced by uniaxial cold compaction. Processing the data recorded during compaction, the mean relative density corresponding to the beginning of prevailing plastic deformation has been identified for all the powder mixes by means of a recursive procedure. The mechanisms responsible for the different transition thresholds have been studied in depth.

Keywords: Compaction mechanics | Particle size | Uniaxial cold compaction

[13] Cristofolini I., Molinari A., Zago M., Pederzini G., Rambelli A., The analysis of the densification curve of metallic powders in uniaxial cold compaction, Advances in Powder Metallurgy and Particulate Materials - 2019: Proceedings of the 2019 International Conference on Powder Metallurgy and Particulate Materials, 30-41, (2019). Abstract
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Abstract: Several models have been proposed in literature for decades to describe the relationships between the compaction pressure and green density. Some of them are almost empirical, others are based on a theoretical approach starting from the phenomena occurring during cold compaction. The authors of the present paper have recently (2018) proposed a model based on the investigation of the deformation experienced by the powder mix when subject to the application of the compaction pressure. In this work, the model is compared with the three most recently published ones: the Aryanpour and Farzaneh model (2015), evaluating the contribution of rearrangement; the Parilak et al. model (2017) that was validated with experimental data relevant to 205 powder mixes, and the Montes et al. equation (2018) that was developed considering the local stress and strain in the interparticle contacts. Compaction experiments were carried out on a commercial AISI 316L stainless steel powder mix, sieved in different particle size ranges, and the data collected by the compaction press control unit were used.

[14] Zago M., Molinari A., Rambelli A., Pederzini G., Cristofolini I., Study of the influence of geometry and particle size on the densification and compaction mechanics of uniaxially cold compacted rings, International Journal of Powder Metallurgy, 55(3), 29-38, (2019).
[15] Baselli S., Torresani E., Zago M., Amirabdollahian S., Cristofolini I., Molinari A., Sintering shrinkage of uniaxial cold compacted iron: influence of the microstructure on the anisothermal and isothermal shrinkage of uniaxial cold-compacted iron, Powder Metallurgy, 61(4), 276-284, (2018). Abstract
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Abstract: The influence of the microstructure of uniaxial cold-compacted green iron on the sintering shrinkage was investigated. Pores in the green parts are very slightly oriented, while the dimension of the interparticle contact areas is anisotropic. A large and anisotropic anisothermal shrinkage in alpha iron was measured, greater than isothermal shrinkage at the 1120°C. The results were interpreted on the basis of the geometrical and of the structural activity, and the effective diffusivity responsible for neck growth was determined.

Keywords: anisotropy | microstructure | Shrinkage

[16] Molinari A., Amirabdollahian S., Zago M., Larsson M., Cristofolini I., Effect of geometry and green density on the anisotropic sintering shrinkage of axisymmetric iron parts, Powder Metallurgy, 61(4), 267-275, (2018). Abstract
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Abstract: Sintering shrinkage of prior cold compacted iron rings with different geometry (height to wall thickness ratio) and green density in the 6.5–7.3 g/cm3 range was investigated. It displays a minimum at an intermediate green density. Axial, tangential and radial shrinkages are different, due to the gradients of green density along the axial and the radial directions. Therefore, the effect of height on shrinkage and its anisotropy is the result of their effect on the stress distribution in the green parts during cold compaction, and the resulting green density and deformation experienced by the powder. Anisotropy decreases on increasing shrinkage.

Keywords: geometry | green density | Shrinkage anisotropy

[17] Zago M., Cristofolini I., Molinari A., Pederzini G., Rambelli A., Processing method to improve the reliability of data recorded by an industrial press in describing powder behavior during uniaxial cold compaction, Euro PM 2018 Congress and Exhibition, (2018). Abstract
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Abstract: In previous work the data recorded by an industrial press (forces and displacements) were extensively used to describe powder behavior during uniaxial cold compaction. Satisfactory models describing densification were proposed, as the result of the axial and radial stresses acting on the powder column. The recorded data are very precise from an industrial perspective, mainly in the last stage of compaction, directly related to final green density. Nevertheless, they are slightly scattered in the first stage, which is interesting from a scientific perspective, as the step where rearrangement occurs. To overcome this limit, this work proposes a methodology to analyze the signal of forces in the frequency domain to increase the signal to noise ratio. The signal was decomposed through the Fourier transformation, and the noise was smoothed by a low-pass filter specifically designed for the press. Reliability of the data and effectiveness of the derived relationships result significantly improved.

Keywords: Compaction mechanics | Signal analysis | Smoothing operation

[18] Cristofolini I., Molinari A., Zago M., Amirabdollahian S., Coube O., Dougan M.J., Larsson M., Schneider M., Valler P., Voglhuber J., Wimbert L., Design for Sintering club project - Dealing with the anisotropy of dimensional changes in real parts, Euro PM 2018 Congress and Exhibition, (2018). Abstract
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Abstract: In previous work the anisotropic dimensional change on sintering has been investigated in depth. An anisotropy parameter has been identified, depending both on geometry and on sintering conditions, and it has been used to define a model for the anisotropic behaviour. A design procedure accounting for anisotropic dimensional changes has been proposed. This work summarizes the main results obtained within the Design for Sintering Club Project, aimed at validating and enlarging the aforementioned design procedure by the application on real industrial parts. Project partners provided axi-symmetric parts, which were measured both in the green state and after sintering in standard industrial conditions. The real dimensional changes were compared to the dimensional changes predicted by means of the design procedure based on the anisotropy model. The results, also compared to the attainable dimensional tolerances, allowed validating the design procedure, and showing directions to further improvement.

Keywords: Anisotropy | Design for sintering | Dimensional change

[19] Molinan A., Zago M., Amirabdollhaian S., Cnstofolim L., From compaction mechanics to sintering shrinkage of rings with different h/(d<inf>ext</inf>-d<inf>int</inf>) ratio, Advances in Powder Metallurgy and Particulate Materials - 2018: Proceedings of the 2018 International Conference on Powder Metallurgy and Particulate Material, POWDERMET 2018, 2018-June, 81-90, (2018). Abstract
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Abstract: The sintering shrinkage of AISI316L rings with different height was correlated to the stress field applied to the powder mix dunng prior cold compaction. Both the stress field and the sintering shrinkage are isotropic in the compaction plane, while anisotropic along the axial direction with respect to the radial and tangential directions. A clear correlation between shrinkage and compaction stress was individuated, both from the mean analysis and from the local analysis; the higher the compaction stress, the higher the sintering shrinkage Such a correlation was used to predict the axial shrinkage theoretically. The anisotropy of shrinkage was correlated with the deviatonc component of the stress field.

Keywords: Compaction mechanics | Sintering shrinkage

[20] Cristofolini I., Molinari A., Zago M., Pederzini G., Rambelli A., Delia Ricca R.C.F., The influence of lubricant on the constitutive model of low alloy steel powder mix, Advances in Powder Metallurgy and Particulate Materials - 2018: Proceedings of the 2018 International Conference on Powder Metallurgy and Particulate Material, POWDERMET 2018, 2018-June, 55-66, (2018). Abstract
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Abstract: Compaction mechanics has been investigated in previous work using the data continuously recorded by an industrial press, aiming at obtaining the constitutive model of powder mixes actually representing powder behaviour during uniaxial cold compaction. The influence of geometry and powder mix has been previously investigated. In this work the same experimental approach was followed, aiming at highlighting the influence of the lubricant admixed to the metal powder. Two different lubricants, in two different amounts have been added to a commercial diffusion bonded low alloy steel powder. Different compaction strategies have been used to produce ring shaped parts, characterized by different H/(Dext-Dmt) ratios (0.5, 1,1.5, 2) and different green densities (6.7, 6.9, 7.1 g/cm3). The recorded data have been used to derive the mechanics relationships governing densification for each powder mix. The results have been compared to highlight the innuence of lubricant type and amount.

[21] Molinari A., Zago M., Amirabdollahian S., Cristofolini I., Larsson M., Anisotropic sintering shrinkage of ring shaped iron parts: Effect of geometry and green density and correlation to the stress field during uniaxial cold compaction, Proceedings Euro PM 2017: International Powder Metallurgy Congress and Exhibition, (2017). Abstract
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Abstract: Sintering shrinkage of uniaxially cold compacted axi-symmetrical parts is anisotropic. Not only is the shrinkage of height (parallel to the compaction direction) different from that of the diameters (in the compaction plane), but even the dimensional changes of the inner and of the outer diameters differ significantly. This behaviour has been investigated on iron rings with different geometry and green density. In the compaction plane radial and tangential shrinkages are different, and tangential shrinkage significantly changes along the wall thickness. This is due to the distribution of radial and tangential stresses during cold compaction that in turn depends on the axial stress. The stress field and its dependence on both green density and geometry were hypothesized to propose a working direction to interpret the anisotropy of sintering shrinkage in real parts.

Keywords: Geometry | Green density | Sintering shrinkage

[22] Cristofolini I., Molinari A., Zago M., Pederzini G., Rambelli A., The influence of H/T ratio on the densification model of aisi 316L powder during uniaxial cold compaction, Advances in Powder Metallurgy and Particulate Materials 2017 - Proceedings of the 2017 International Conference on Powder Metallurgy and Particulate Materials, 2017-June, 30-40, (2017). Abstract
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Abstract: In previous works the deformation of the powder column during uniaxial cold compaction was studied by means of experimental data, also deriving relationships with densification and the axial and radial stresses distribution. Cylindrical specimens were considered in all the previous works. Aiming at enlarging the field of application of the results, obtained by the data continuously recorded by an industrial press without any additional device, the influence of geometry is investigated in this work. Rings characterised by different H/T ratios (Height on Thickness equal to 1, 2, 3, 4), considerably higher than in the previous works, were produced using different compaction strategies. Densification curves are derived, where density is reported as a function of the pressure applied by the upper punch, also highlighting density gradients. The deformation of the powder column is derived from experimental data and related to the densification. The results are compared with those obtained investigating cylindrical specimens.

[23] Fedel M., Poelman M., Zago M., Vandermiers C., Cossement D., Olivier M.G., Deflorian F., Influence of formulation and application parameters on the performances of a sol-gel/clay nanocomposite on the corrosion resistance of hot-dip galvanized steel. Part II. Effect of curing temperature and time, Surface and Coatings Technology, 274, 9-17, (2015). Abstract
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Abstract: The study deals with the investigation of a sol-gel/nanoclay composite coating as a protective layer for the corrosion protection of hot dip galvanized (HDG) steel. Sol-gel coatings prepared from glycidoxypropyltrimethoxysilane, tetraethoxysilane and methyltriethoxysilane with 2. wt.% of sodium montmorillonite were investigated. The effect of different curing times (2, 5, 10, 15. min) and different curing temperatures (90 °C, 150 °C, 180 °C) on the protection properties of the hybrid layer was investigated. ToF-SIMS analyses and FT-IR measurements highlighted that the higher is the curing temperature, the higher is the densification of the sol-gel network. FT-IR spectroscopy measurements underlined that the Si-O-Si/Si-OH ratio rises by increasing curing time or temperature. ToF-SIMS analyses indicate a lessening in the coating thickness by increasing the curing temperature. The densification of the network through formation of siloxane bonds was found to be responsible for the improved protection offered by the sol-gel layer which leads to a remarkable drop of the cathodic current density and an increase of the resistance associated to the sol-gel film.

Keywords: Corrosion | EIS | FT-IR | HDG | Sol-gel