Journal of Materials Processing Technology 246 (2017) 93–101 Contents lists available at ScienceDirect Journal of Materials Processing Technology jo ur nal ho me page: www.elsevier.com/locate/jmatprotec Effect of the current pulse pattern during heating in a spark plasma sintering device: Experimental and numerical modeling approaches J. Diatta a,∗ , G. Antou a , F. Courreges b , M. Georges a , N. Pradeilles a , A. Maître a a Univ. Limoges, CNRS, ENSCI, SPCTS, UMR 7315, F-87000 Limoges, France b Univ. Limoges, CNRS, XLIM/SRI, UMR 7252, F-87000 Limoges, France a r t i c l e i n f o Article history: Received 26 August 2016 Received in revised form 27 February 2017 Accepted 6 March 2017 Available online 8 March 2017 Keywords: Spark plasma sintering Pulse pattern Thermal and electrical measurement Modeling FEM a b s t r a c t The operating features of the current generator during Spark Plasma Sintering (SPS) process are care- fully studied thanks to the use of a specific instrumentation. It is shown that the current pulse pattern characteristics identified here for a Dr. Sinter 825 apparatus are transposable to other Dr. Sinter devices whatever their electrical powers. Particularly, thanks to the highlighting of the characteristic logarith- mic decrease of the ratio of rms to average electrical values, it is possible, for users of SPS devices, to determine the imposed rms intensity from the average intensity measured by the galvanometer of the apparatus without additional electrical instrumentation. Moreover, as shown by a numerical approach, the delivered rms intensity directly correlated to the pulse pattern characteristics is a key parameter that controls the heating process induced by the Joule effect. Hence, a reliable numerical model is established with an accurate assessment of the heating rate and of the thermal gradients. © 2017 Elsevier B.V. All rights reserved. Introduction Spark Plasma Sintering (SPS), also known as Field Assisted Sin- tering Technique (FAST) or Pulsed Electric Current Sintering (PECS), belongs to a class of sintering techniques that uses an electric cur- rent to activate sintering (Munir et al., 2006). This technique, which is based on the simultaneous application of high temperature, high electric current intensity (low voltage) leading to a high heating rate (up to 1000 ◦ C min −1 ) and high axial pressure, is an attractive sin- tering technique, since it allows densification under shorter cycle times compared to other pressure-assisted sintering processes (i.e. hot uniaxial pressing or hot isostatic pressing) (Orrù et al., 2009). SPS provides accelerated densification and, due to its shorter cycle time, limited and/or controlled grain growth. However, the whole of the physical phenomena promoted by the pulsed direct current (DC) and the high heating rates are not fully understood (Antou et al., 2015a, 2015b). The high heating rates in SPS leads to a complex temperature distribution within the die. The estimation of a specimen temperature by a pyrome- ter that measures a die surface temperature leads to an incorrect evaluation, often an underestimation, as previously shown by (Antou et al., 2009; Zavaliangos et al., 2004). The evaluation of ∗ Corresponding author. E-mail address: joseph.diatta@unilim.fr (J. Diatta). temperature distribution during SPS remains critical: (i) to allow for a proper comparison with traditional sintering techniques (Zavaliangos et al., 2004); (ii) to optimize processing of a larger specimen, where the presence of temperature gradients within the sample may lead to a microstructural inhomogeneity and finally to non-uniform working properties of the sintered parts (Voisin et al., 2013). Through Fourier’s transformation of the pulse pat- tern, Anselmi-Tamburini et al. (Anselmi-Tamburini et al., 2005a) have shown that most of the overall heating power in the SPS is produced by components with frequencies below 100 Hz. So, the current fluxes and temperature generation can be modeled numer- ically by considering a constant DC as a very good approximation. In the literature, finite element (FE) simulations have been cou- pled to temperature measurements in order to understand and analyze the temperature distribution and to identify the control- ling parameters of the SPS process (Cincotti et al., 2007; Manière et al., 2016a,b; Vanmeensel et al., 2005; Voisin et al., 2013). More recently, works of the literature (Charles Manière et al., 2016a,b; Mondalek et al., 2011; Olevsky et al., 2012; Song et al., 2011; Wolff et al., 2012, 2016) focused on the development of fully coupled electro-thermo-mechanical models that integrate the densification process of the powder. However, these numerical approaches needs a better understanding of an aspect often neglected, which is the relationship between the operating features of the pulsed current generator and the induced temperature field. http://dx.doi.org/10.1016/j.jmatprotec.2017.03.004 0924-0136/© 2017 Elsevier B.V. All rights reserved.