The objective of the present study was to investigate the spark plasma sintering technology when a pure coarse aluminium powder is used. In order to understand the process, different conditions of temperature, current flow through the sample, pressure and delay at which the pressure is applied were investigated to clarify the role of the pulsed electric current. It has been shown that the presence of the current flow and applying the sintering pressure with a certain delay in respect to the beginning of the cycle promote better sintering and mechanical properties. With a heating rate of 100 K min 21 , a sintering temperature of 525uC, dwell time of 1 min and pressure of 60 MPa, the mechanical properties and the fracture morphology are very similar to those of pure annealed wrought aluminium.

Titanium alloys are of great interest for several applications, but their processing and application is often difficult and expensive. Metal powder processing permits the reduction of material costs because of limited wasting, even if, sintering of titanium powders has to be carried out under controlled atmospheres, with high processing costs. Spark plasma sintering (SPS) is a new technology which permits processing of hard to sinter materials at lower temperatures and in shorter time compared to conventional technologies; furthermore, SPS can be seen as a potential near net shaping production route for non-complex components. In the present work, the use of SPS on commercial purity titanium grade 1 and grade 3 was investigated. Sintering experiments were conducted in the temperature range 700-1150uC for 5 min, under a uniaxial pressure of 60 MPa, in vacuum. Samples obtained at different temperatures were characterised in term of density, microstructure (grain size), interstitial content (C,O,N), hardness, tensile properties; SEM analysis on fracture surfaces of tensile specimen was also carried out. Results were critically discussed and correlated to sintering temperature, in respect to the typical aRb transformation temperature for each grade. Experimental data confirm that very good microstructural, chemical and mechanical properties can be attained after spark plasma sintering at temperature as low as 900uC.

No abstract

No abstract

No abstract