Control of porosity and superelasticity of porous NiTi shape memory alloys prepared by hot isostatic pressing

• Published in: Smart materials and structures Vol. 14; no. 5; pp. S201 - S206
• Main Authors: Yuan, B, Chung, C Y, Zhang, X P, Zeng, M Q, Zhu, M
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.10.2005; Institute of Physics
• Subjects: Exact sciences and technology; Fundamental areas of phenomenology (including applications); General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Measurement and testing methods; Physics; Servo and control equipment; robots; Solid mechanics; Structural and continuum mechanics; Powders; Phase transformations; Hot isostatic pressing; Martensitic transformations; Mechanical properties; Crack propagation resistance; Capsules; Shape memory alloy; Granular materials; Ambient temperature; Porosity; Isotropic material; Nitinol
• ISSN: 0964-1726; 1361-665X
• DOI: 10.1088/0964-1726/14/5/005

Porous Ni-rich NiTi SMAs have been successfully prepared from elemental Ni and Ti powders, using capsule-free hot isostatic pressing processing. The fabricated alloys have isotropic and uniform pore distributions of spherical pores ranging from 50 to 200 mm. The porosities of these NiTi alloys range from 30 to 40% by volume. The microstructure, martensitic transformation behaviors and mechanical properties of the fabricated porous NiTi SMAs aged under different conditions were studied. It has been found that the phase transformation behaviors of porous NiTi SMAs are similar to those of conventionally cast Ni-rich NiTi alloys. It is encouraging that the porous NiTi SMAs exhibit excellent superelasticity at room temperature after the appropriate thermomechanical treatment. Experimental results reveal that the superelasticity, which is controlled by the pore characteristics, such as pore shape, pore size and pore distribution, is important for improving the toughness, elastic properties and compression strength of the porous NiTi SMAs.