Abstract
Rare-earth containing magnesium alloy AE42 was prepared by powder metallurgy technique of spark plasma sintering for the first time. The effect of sintering parameters on the microstructure, precipitation of secondary particles and mechanical properties was investigated.
The gas-atomized AE42 alloy powder was sintered at three different temperatures of 450 degrees C, 500 degrees C and 550 degrees C for three minutes, which was sufficient to achieve almost full density. Despite the negligible effect of the sintering temperature on the grain size, sintering had a pronounced effect on the Al11RE3 secondary phase particles.
Fine eutectic lamellar structure of Al11RE3 in gas-atomized powder transformed to almost globular particles during SPS and size of these secondary phase particles increased with increasing sintering temperature. As the result, SPS temperature had significant effect on the mechanical strength of the material via altering the size and morphology of Al11RE3 particles.
Sintered material was compared with the gas-atomized powder subsequently annealed at 550 degrees C. It was found that the kinetics of the globularization of the Al11RE3 secondary phase particles is much faster during spark plasma sintering than during conventional annealing at the same temperature.
This can be associated with increased diffusivity along the matrix/precipitate interface or possibly with locally increased temperature due to electron transport.