G.A. Song

Investigation of the mechanical properties of Ti-Fe-Sn ultrafine eutectic composites by dendrite phase selection

Microstructural investigation of Ti-Fe-Sn ultrafine eutectic composites reveals that β-Ti primary dendrite in eutectic matrix consists of TiFe and β-Ti for Ti72Fe22Sn6 alloy. Similarly, the Ti64Fe32Sn4 alloy and Ti68Fe23Sn9 alloy consists of TiFe and Ti3Sn micron-scale primary dendrites uniformly embedded in the TiFe and β-Ti eutectic structure. The β-Ti dendrite was formed in Ti72Fe22Sn6 alloy, the large number of shear bands propagation and makes multiple steps on the fracture surface. The Ti3Sn dendrite in Ti68Fe23Sn9 ultrafine eutectic alloy leads slip bands which induce the work hardening that have important role in plasticity during deformation. On the other hand, TiFe dendrite in Ti64Fe32Sn4 alloy was presented shear bands bypass and extinction while the propagation of shear bands. These microstructural changes lead to different deformation behavior in primary dendrite. Therefore, it is believed that the mechanical properties of Ti-Fe-Sn alloys could improve due to a different deformation behavior through the minute compositional tuning of Ti-Fe-Sn alloys.

FABRICATION OF POROUS Ti- AND W-COMPACTS BY ELECTRO-DISCHARGE-SINTERING PROCESS

A single pulse of 0.57–1.1 kJ/0.3 g-spherical Ti-powder in size range of 30–70 μm, using a constant 450 μF capacitor, was applied to produce fully porous Ti- and W-compacts by electro-discharge sintering. Microstructure examination and hardness measurement of the porous Ti-compacts revealed that more stable necks formed with increasing electrical input energy up to 1.1 kJ. On the contrary, W-compacts using rectangular W-powders in size range of 5–15 μm are composed of solid region with micropore and porous layer with weak particle bonding indicating heterogeneous structure. These results suggest that the powder morphology plays a crucial role to control the porous microstructure.