In situ formation of Ti alloy/TiC porous composites by rapid microwave sintering of Ti6Al4V/MWCNTs powder

摘要

The rapid in situ formation of a Ti alloy/TiC porous composite was achieved using the powder metallurgy approach. Ti6Al4V powders were mixed with 14.5 vol.% of multiwalled carbon nanotubes (MWCNTs) and the particle size of Ti6Al4V was reduced to ∼5 μm by ball milling. The MWCNTs acted as microwave susceptors as well as reactants for the rapid sintering of Ti alloys. The green compact of the Ti6Al4V/MWCNTs powder was sintered in a 1.4 kW, 2.45 GHz bi-directional microwave emission furnace without using any protective gas environment. The microwave sintering was completed within 2 min. The surface temperature of the sample reached 1620 °C during sintering, as measured by a pyrometer. Titanium carbide was formed after the sintering as confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The composite has a porosity of approximately 25%, compressive strength of 270.41 ± 24.97 MPa, compressive yield stress of 145.48 ± 27.28 MPa, compressive Young's modulus of 10.87 ± 2.46 GPa and compressive strain of 3.75 ± 1.11%. The Vickers hardness value in the TiC region (545.4 ± 13.9 HV) is significant higher than that in the Ti alloy region (435.9 ± 12.9 HV). An overall Rockwell hardness of 47 HRA was measured.