Consolidation of Hard Sinterable Materials and Near Net Shape Forming by Pulsed Current Pressure Sintering (PCPS) Process.

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The Pulsed Current Pressure Sintering (PCPS) is well known as rapid sintering process. This is a kind of hot pressing which employs the pulsed electric current to heat materials. It is suggested to be characterized by four major advantages over the conventional consolidation techniques, i.e. : (1) preservation of original microstructures after consolidation, (2) high density consolidation in a short time, (3) removal of adsorbed materials on the powder surface, (4) improved mechanical properties resulted from these (1)-(3) items. We employed the PCPS process to consolidate the aluminum alloy powder and attained the high strength sintered specimen. Furthermore, hollow shaped compacts and functionally graded Al/Al2O3 materials were formed by PCPS. Principal results obtained are as follows :(1) The maximum tensile strength of PCP sintered compact was over 9OMPa and the elongation was 50%. This value outweigh that of 1000 series Al wrought alloys.(2) PCP sintering process can densify Al powders in a short time compared to the HP sintering process. Mechanical properties of the compacts outweigh the HP compact.(3) The hollow compacts having an intricate shape were obtained by a one-pass process of PCPS sintering using the core made of h-BN or graphite powders because of their good compactibility and difficultly sinterable properties.(4) The Al/Al_2O_3 FGM composed of a dense a-Al_2O_3 layer and seven gradient intermediate layers was successfully fabricated from starting materials consisting of aluminum and Al(OH)_3 powders by employing a temperature gradient PSPC process with a copper spacer, at a pressure of 49 MPa, and with the short sintering time of 900 sec. The hardness of the aluminum layer was about 25 HV. The hardness of intermediate layers gradually increased as the volume fraction of r-Al_2O_3 increased. The top layer, which consists of dense a-Al_2O_3, was about 1000 HV on average, and the top surface of the specimen reached 1500 HV.