Phase composition, microstructure, and mechanical properties of porous Ti–Nb–Zr alloys prepared by a two-step foaming powder metallurgy method

• Porous Ti–Nb–Zr alloys with low elastic modulus as human bones are fabricated.
• TiH2 is used as the source powder with adding NH4HCO3 to form pores in substrates.
• Adding Nb–Zr and increasing sintering temperature transform the phase from α to β.
• Increasing NH4HCO3 changes pore characteristics.
• Phase composition and pore characteristics affect mechanical properties.

Porous Ti–Nb–Zr alloys with different porosities from 6.06 to 62.8% are prepared by a two-step foaming powder metallurgy method using TiH2, Nb, and Zr powders together with 0 to 50 wt% of NH4HCO3. The effects of the amounts of Nb and Zr as well as the sintering temperature (1473 to 1673 K) on their phase composition, porosity, morphology, and mechanical characteristics are investigated. By controlling the porosity, Nb and Zr concentrations as well as the sintering temperature, porous Ti–Nb–Zr alloys with different mechanical properties can be obtained, for example, the hardness between 290 and 63 HV, the compressive strength between 1530.5 and 73.4 MPa, and the elastic modulus between 10.8 and 1.2 GPa. The mechanical properties of the sintered porous Ti–Nb–Zr alloys can be tailored to match different requirements for the human bones and are thus potentially useful in the hard tissue implants.