690 1068-1302/12/1112-0690  2012 Springer Science+Business Media, Inc. Powder Metallurgy and Metal Ceramics, Vol. 50, Nos. 11-12, March, 2012 (Russian Original Vol. 50, Nos. 11-12, Nov.-Dec., 2011) THEORY AND TECHNOLOGY OF SINTERING, THERMAL AND CHEMICOTHERMAL TREATMENT ELECTRICAL ASPECTS OF THE SPARK-PLASMA SINTERING OF TiN–TiB 2 COMPOSITE. II. EFFECT OF ALTERNATING CURRENT ON THE SPARK-PLASMA SINTERING OF TiH 2 + BN POWDER MIXTURE A. S. Petukhov, 1 I. V. Khobta, 1 A. V. Ragulya, 1,2 A. V. Derevyanko, 1 and V. V. Starchenko 1 UDC 621.762 The effect of alternating current on the formation of phases and structure during the synthesis of TiN + TiB 2 composite by spark-plasma sintering of TiH 2 + BN powder mixtures employing a superposition of alternating and direct currents is studied. The sintering leads to composites with semiconductor and dielectric phases (Ti and BN oxides) if a direct current is used and to TiN + TiB 2 composite with metallic conductivity if a superposition of direct and alternating currents is used. The alternating current intensifies the ion electromigration between particles during spark discharge. This accelerates the decomposition of -BN by atomic hydrogen and, as a result, intensifies the formation of TiN + TiB 2 composite. Keywords: TiN + TiB 2 , spark-plasma sintering, superposition of alternating and direct currents, spark discharge. INTRODUCTION The physical and chemical processes accompanying spark-plasma sintering (SPS) are largely determined by the behavior of electric current load [1]. The reactive SPS of TiH 2 + BN powder mixture to produce TiN + TiB 2 composite was studied in [2–4]. Spark-plasma sintering is compaction under low pressure (to 100 MPa), which causes spark discharge between particles of the powder at a certain potential difference. This process is accompanied by intensive heating due to ionic collisions between and with particles, diffusion processes in solid particles and on their surfaces, and ion electromigration between particles under the action of the electric field [1]. The collisions of ions and the considerable increase in the temperature on the surface of powder particles cause intensive removal of oxides from 1 Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Kiev, Ukraine. 2 To whom correspondence should be addressed; e-mail: ragulya@ipms.kiev.ua. Translated from Poroshkovaya Metallurgiya, Vol. 50, No. 11–12 (482), pp. 19–28, 2011. Original article submitted April 14, 2011.