Papers by Author: Jakub Jaroszewicz

Abstract: X-ray micro-computed tomography system has been used for visualization in two- (2-D) and three dimensions (3-D) of the dendrite structure and pores in single-crystals fabricated by Bridgman investment casting technique. The system described in the paper reconstructs 3-D geometry from a set of 2-D images obtained by multiple slicing of an X-ray radiography image. The results obtained in this study demonstrate the effect of withdrawal rate on the primary dendrite arm spacing and porosity in single-crystal made of CMSX-4 alloy.

Abstract: Nanocrystalline WC-12wt.%Co was consolidated by Pulse Plasma Sintering (PPS) at various temperatures between 900 and 1200oC for 6 minutes under a pressure of 60MPa. Cemented carbides sintered at 1100oC have a relative density of 99%, a hardness of 2248HV30, the fracture toughness, KIC=12.5 MPa*m1/2, and have a structure containing 50nm WC crystallites. Increasing the sintering temperature to 1200oC causes an increase in the size of the WC crystallite size to about 110 nm, reduces the hardness to 2198HV30, and decreases the KIC to 9.7 MPa*m1/2.

Abstract: Nanocrystalline copper powders, produced by the reduction of the CuO with hydrogen, were consolidated using the pulse plasma sintering (PPS) method. The sintering process was carried out at temperatures between 500 and 900 oC under a load of 60 MPa for 5 min. The average crystallite size of the sintered component obtained at 500 oC was about 80nm and at 900 oC 1880 nm. The components produced at 500 oC had a relative density of 90 %, and those sintered at 900 oC 92 %; their hardness was 215 and 140 HV0.1, respectively.

Abstract: The paper presents the results of examination of the structure and properties of nanocrystalline Cu-Al2O3 composites with the two different Al2O3 contents: 10 and 20 vol.%. The composites were produced using a mixture of copper and Al2O3 powders with an average crystallite size of about 60nm for Cu and about 40nm for Al2O3. The powders were consolidated by pulse plasma sintering (PPS) for 5 minutes at a temperature of 650oC under a load of 60 MPa. Irrespective of the volumetric content of Al2O3, the relative density of the composites was about 92%, and the average Cu crystallite size was about 80nm. The hardness of the composites varied with the volumetric content of Al2O3, and was equal to 270 HV0.1 for 20 and to 240 HV0.1 for 10% of Al2O3. The Cu-20%Al2O3 composite had a resistivity of 0.386 while that with 10% of Al2O3 was 0.149 56m.