Effect of Zr addition and cold-rolling deformation on microstructure and mechanical properties of TiNi alloys

The Ti50-0.5 x Ni50-0.5 x Zr x series alloys were prepared by vacuum arc melting and subsequent suction casting. Metallographic observation and tensile mechanical tests show that adding trace amount of Zr can reduce grain size and increase higher tensile strength and elongation， however， excessive Zr content can easily lead to the formation of brittle intermetallic compound Zr2Ni and reduce its mechanical properties. The multi-pass cold-rolling deformation and annealing treatment on Ti49.9Ni49.9Zr0.2 alloy were carried out. The results show that the tensile strength σ b and the elongation δ of the Ti50－0.5 x Ni50－0.5 x Zr x alloys increase with the increase of cold-rolling deformation. Compared with the unrolled alloys， after four-passes cold-rolling deformation， the tensile strength and the elongation after fracture of the alloys increase from 561 MPa，1.14% to 768 MPa，35.1%，respectively.Microscopic observation of SEM and TEM show that the hard Ti2Ni particles distributed along the grain boundaries during the