Nanoindentation mechanical properties on spark plasma sintered 48Ti-48Al-2Cr-2Nb alloy

This study aims to investigate the microstructure, plastic (H) properties, elastic (E) properties, reduced elastic (Er) properties the strain-to-break parameter (H/Er), and the resistance to plastic deformation parameter (H3/Er2) of the Ti-48Al-2Cr-2Nb alloy by use of scanning electron microscopy, nanoindentation and micro-indentation techniques. The results show that the sintering parameters had significant effect on the resulting microstructure. Desirable mechanical properties were obtained with the sample sintered at temperature of 1200 °C, pressure of 50 MPa, holding time of 7.5 min and a heating rate of 50 °C/min which had a near lamellar structure, resulting from the grain boundary pinning effect of the fine equiaxed gamma grains and the impartation of ductility due to the coarsened lamellar colonies. The nano-hardness and elastic modulus were observed to be about 4GPa and 31GPa for the near lamellar microstructure, respectively, with the microhardness of about 4.4GPa. While the duplex and the near gamma microstructures possessed the least nano-hardness (3.65-3.78GPa) and elastic modulus (3.6-29.5GPa) with the exception of sample sintered at temperature of 1150 °C, pressure of 50 MPa, holding time of 7.5 min and a heating rate of 100 °C/min., with nano-hardness and elastic modulus of 4.05GPa and 31.25GPa, respectively, however it had the lowest micro-hardness of 2.7GPa. Furthermore, the ratios H/Er and H3/Er2 values were observed to be greater for the same sample suggesting good wear resistance of the alloy.