Mechanically activated reactive forging synthesis (MARFOS) of NiTi

作者：Neves F^*; Martins I; Correia J B; Oliveira M; Gaffet E

来源：Intermetallics, 2008, 16(7): 889-895.

DOI：10.1016/j.intermet.2008.04.002

• intermetallics, miscellaneous
• mechanical alloying and milling
• isothermal forging
• powder metallurgy

The production of NiTi alloys through mechanically activated reactive forging synthesis (MARFOS) of elemental powder mixtures with equiatomic composition has been investigated for the first time. The short duration of mechanical activation (4 h) successfully produced powder mixtures capable of being hot deformed at relatively low temperatures. As a consequence, a bulk product constituted by intermetallic and metallic nanocrystalline phases was effectively obtained at 700 degrees C. An additional heat treatment at 950 degrees C/24 h removed almost all the undesired phases and maintained the nanocrystalline structure, resulting in an Ni-rich NiTi matrix containing some Ti(2)Ni/Ti(4)Ni(2)O(x) and having a microhardness of 708 H(V)0.3. The formation of such microstructure may be attributed to the presence of oxygen and nitrogen impurities in the materials. After ageing at 500 degrees C/48 h, some degree of compositional rectification was achieved in the NiTi matrix due to the formation of Ni(4)Ti(3) precipitates.

• 出版日期2008-7