Spark-plasma-sintering and finite element method: From the identification of the sintering parameters of a submicronic α-alumina powder to the development of complex shapes

Zhao

et al. 2017

Sci Rep

Multifunctional materials with more than two good properties are widely required in modern industries. However, some properties are often trade-off with each other by single microstructural designation. For example, nanostructured materials have high strength, but low ductility and thermal stability. Here by means of spark plasma sintering (SPS) of nitrided Ti particles, we synthesized bulk core-shell structured Ti alloys with isolated soft coarse-grained Ti cores and hard Ti-N solid solution shells. The core-shell Ti alloys exhibit a high yield strength (~1.4 GPa) comparable to that of nanostructured states and high thermal stability (over 1100 °C, 0.71 of melting temperature), contributed by the hard Ti-N shells, as well as a good plasticity (fracture plasticity of 12%) due to the soft Ti cores. Our results demonstrate that this core-shell structure offers a design pathway towards an advanced material with enhancing strength-plasticity-thermal stability synergy.

Section: Resultsmentioning

confidence: 84%

Core-shell structured titanium-nitrogen alloys with high strength, high thermal stability and good plasticity

Zhao

et al. 2017

Sci Rep

Journal of the European Ceramic Society

“…The shrinkage curves introduced into the model (Fig. 3) are calculated by an analytic Olevsky's model for sintering [18] previously determined for our alumina powder [19]. The Table 1 Physical properties of inconel, graphite and alumina (with T in Kelvin).…”

Section: The Joule Heating Modelmentioning

confidence: 99%

“…The punch/die ECR is globally modelled here by a resistive layer with an anisotropic effective electrical resistivity e ( ex , ey ) of thickness 0.2 mm, corresponding to the initial punch/die gap where the papyex is introduced, which is assumed constant (19).…”

Section: Spacer/punch Punch/sample Sample/die and Punch/die Calibramentioning

confidence: 99%

Contact resistances in spark plasma sintering: From in-situ and ex-situ determinations to an extended model for the scale up of the process

Manière

Durand

Brisson

et al. 2017

Self Cite

, et al.. Contact resistances in spark plasma sintering: From in-situ and ex-situ determinations to an extended model for the scale up of the process. Journal of the European Ceramic Society, Elsevier, 2017, vol. 37 (n°4) b s t r a c tHeating in spark plasma sintering is a key point of this manufacturing process that requires advanced simulation to predict the thermal gradients present during the process and adjust them. Electric and thermal contact resistances have a prominent role in these gradients. Their determination is difficult as they vary with pressure and temperature. A calibration method is used to determine all of the contact resistances present within tools of different sizes. Ex situ measurements were also performed to validate the results of the in-situ calibrations. An extended predictive and scalable contacts model was developed and reveals the great importance and diversity of the contact resistances responsible for the general heating of the column and high thermal gradients between the parts. The ex/in situ comparison highlights a high lateral thermal contact resistance and the presence of a possible phenomenon of electric current facilitation across the lateral interface for the high temperatures.

“…We showed in a previous work [30] that this intrinsic difficulty is responsible for densification inhomogeneity for all die compaction type processes. In a complex shape, the areas of small thickness need lesser densification distance than the high thickness area.…”

Section: Introductionmentioning

confidence: 99%

“…The main difficulty of the multiple parts configurations is the temperature homogeneity. Finite Element Method (FEM) simulations of the Joule heating [12][13][14][15][16][17][18][19][20][21][22] and the densification [23][24][25][26][27][28][29][30] are performed by many authors, with the aim of predicting the temperature and densification field and find optimized solutions [10,[31][32][33][34][35][36]. In previous work [11], we showed that a homogenization of the temperature field can be attained for multiple parts configurations by adjusting the electric current flow with electric insulations and specific geometrical tricks.…”

Section: Introductionmentioning

confidence: 99%

Spark plasma sintering and complex shapes: The deformed interfaces approach

Manière¹,

Nigito²,

Durand³

et al. 2017

Powder Technology

Self Cite

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. a b s t r a c tOver the last few decades, the SPS technique has proven its benefits in terms of microstructure control, reduction of cycling time and a general stability of the results. However, to overcome the so-called "valley of death" between fundamental research and successful industrialization, the next step is to prove the ability of this technology to perform the total densification of highly complex shape samples. The elaboration of complex shapes with die compaction processes often present densification inhomogeneity because of the thickness differences of the sample. In this paper, we present a method to solve this problem with an approach we called the "deformed interfaces method" that uses sacrificial materials. This method can be generalized to all the pressure assisted sintering techniques and allow a complete densification whatever the shape complexity of the part. This method is tested with different materials (Al, CoNiCrAlY, PMMA, Al 2 O 3 , 4Y-ZrO 2 ) and shapes. To prove the effectiveness of this method on very high complex shapes, a 98% dense turbine blade shape has been made.