High–strength porous TiNbZrTaFe alloys fabricated by sintering of nanocomposite powder precursor with space holder technique

Although introducing high porosity in biomedical Ti alloys can reduce their elastic modulus and promote new bone ingrowth, relieving the stress–shielding effect and implant failure, this also causes a decline in the alloys’ mechanical strength. In this work, a new preparation method for the high–strength and high–porosity Ti65Nb23.33Zr5Ta1.67Fe5 (TNZTF, at.%) alloy was suggested by sintering nanocomposite powder precursor in combination with the use of a space holder technique, in which NH4HCO3 is adopted to achieve a porous structure. The highly porous TNZTF alloy possesses a homogeneous fine–grained microstructure consisting of equiaxed α–Ti and a small amount of FeTi2, the latter of which is distributed in the β–Ti matrix. Through adjusting the mass fraction of NH4HCO3, a novel high–porosity, and high–strength TNZTF alloy with a low modulus was successfully prepared. The porous alloy with the addition of 30 wt.% NH4HCO3 exhibits a porosity of 50.3 ± 0.2%, a maximum strength of 327.3 ± 2.1 MPa, and an elastic modulus of 12.2 ± 0.3 GPa. The strength enhancement is mainly attributed to the unique fine–grained microstructure, which is obtained by the crystallization of the amorphous phase and the ductile–brittle mixed fracture mechanism. The prepared porous TNZTF alloy possesses higher mechanical strength and well–matched elastic modulus, showing great potential as an implant material.