Eng. & Tech. Journal, Vol. 28, No.5 , 2010 * Applied Science Department, University of Technology /Baghdad 992 Characterization of Ni-Ti Shape Memory Alloys Sheelan R. Areef* Received on:25/6/2009 Accepted on:3/12/2009 Abstract Master Samples NiTi (without additives) prepared using powder mixture of 55 wt% Ni and 45 wt% Ti by; mixing in a ball mill for two hours, then compacted at 300, 400, 500, 600, 700, and 800 Mpa, and then sintered at 950 o C for 9 hours under controlled atmosphere (argon). The same approach was made for the samples with Mo and Co additions compacted at 800 Mpa. From the results, it was found that compaction pressure has essential effect on; increasing hardness, decreases porosity percentage and corrosion rate. XRD test shows that the sintered samples are consisting of two phases martensite and austenite at room temperatures (mean thermal NiTi shape memory alloy). The Results shown that the hardness property and corrosion rate increased with all weight percentage of additives Mo and Co, and decreases porosity percentage. ﺍﻟﺸﻜل ﺫﺍﻜﺭﺓ ﺴﺒﺎﺌﻙ ﺨﺼﺎﺌﺹNi-Ti ﺍﻟﺨﻼﺼﺔ ﺍﻻﺴﺎﺱ ﺍﻟﻌﻴﻨﺎﺕ ﺘﺤﻀﻴﺭ ﺘﻡNiTi ) ﺍﻻﻀﺎﻓﺎﺕ ﺒﺩﻭﻥ( ﻭﺯﻨﻴﺔ ﺒﻨﺴﺒﺔ ﺍﻟﻨﻴﻜل ﻤﻥ ﺨﻠﻴﻁ ﺒﺎﺴﺘﺨﺩﺍﻡ55 % ﻭﺯﻨﻴﺔ ﺒﻨﺴﺒﺔ ﻭﺍﻟﺘﻴﺘﺎﻨﻴﻭﻡ45 % ﺍﻟﺨﻠـﻴﻁ ﻜـﺒﺱ ﻭﺘﻡ ﺴﺎﻋﺘﻴﻥ ﻟﻤﺩﺓ ﺍﻟﻜﺭﺍﺕ ﺒﻁﺎﺤﻭﻨﺔ ﺨﻠﻁﻬﻤﺎ ﻭﺘﻡ ﻜﺒﺱ ﻀﻐﻁ ﻋﻨﺩ) 300 ، 400 ، 500 ، 600 ، 700 ﻭ800 ( ﻤﻴ ﻋﻨـﺩ ﺍﻟﺘﻠﺒﻴﺩ ﻋﻤﻠﻴﺔ ﺘﻤﺕ ﻭﺒﻌﺩﻫﺎ ﺒﺴﻜﺎل ﻜﺎ ﺤﺭﺍﺭﺓ ﺩﺭﺠﺔ950 o C ﻭﻟﻤﺩﺓ9 ﺍﻻﺭﻜﻭﻥ ﺒﻐﺎﺯ ﻋﻠﻴﻪ ﻤﺴﻴﻁﺭ ﺒﺠﻭ ﺴﺎﻋﺎﺕ. ﺍﻟﻁﺭﻴﻘـﺔ ﻨﻔﺱ ﺍﺴﺘﺨﺩﻤﺕ ﺍﻻﻀﺎﻓﺎﺕ ﻤﻊ ﺍﻟﻌﻴﻨﺎﺕ ﻟﺘﺤﻀﻴﺭ ﺍﻋﻼﻩ) Mo ﻭCo ( ﻋﻨﺩ ﻜﺒﺴﻬﺎ ﻭﺘﻡ800 ﺒﺴﻜﺎل ﻤﻴﻜﺎ. ﺨـﻼل ﻤـﻥ ﺍﻟﺼﻼ ﺯﻴﺎﺩﺓ ﻋﻠﻰ ﺍﺴﺎﺴﻲ ﺒﺸﻜل ﻴﺅﺜﺭ ﺍﻟﻜﺒﺱ ﻀﻐﻁ ﺍﻥ ﻭﺠﺩ ﺍﻟﻨﺘﺎﺌﺞ ﻭﻤﻌـﺩل ﺍﻟﻤﺴـﺎﻤﻴﺔ ﻨﺴﺒﺔ ﻭﺘﻘﻠﻴل ﺩﺓ ﺍﻟﺘﺎﻜل. ﺍﻟﻤﺎﺭﺘﻨﺴـﺎﻴﺕ ﻁـﻭﺭﻴﻥ ﻋﻠﻰ ﺘﺤﺘﻭﻱ ﺍﻟﻤﻠﺒﺩﺓ ﺍﻟﻌﻴﻨﺎﺕ ﺒﺎﻥ ﻴﻭﻀﺢ ﺍﻟﺴﻴﻨﻴﺔ ﺍﻻﺸﻌﺔ ﺤﻴﻭﺩ ﺍﺨﺘﺒﺎﺭ ﺍﻟﻐﺭﻓﺔ ﺤﺭﺍﺭﺓ ﺩﺭﺠﺔ ﻓﻲ ﻭﺍﻻﻭﺴﺘﻨﺎﻴﺕ) ﺍﻟﺤﺭﺍﺭﻴﺔ ﺍﻟﺸﻜل ﺫﺍﻜﺭﺓ ﺴﺒﻴﻜﺔ ﺍﻱ( ﺒـﺎﻥ ﺍﻟﻨﺘﺎﺌﺞ ﺍﻭﻀﺤﺕ ﻜﻤﺎ ﺍ ﻭﻤﻌﺩل ﺍﻟﺼﻼﺩﺓ ﺯﻴﺎﺩﺓ ﺍﻟﻰ ﺘﺅﺩﻱ ﺍﻻﻀﺎﻓﺎﺕ ﻨﺴﺒﺔ ﺯﻴﺎﺩﺓ ﺍﻟﻤﺴﺎﻤﻴﺔ ﻨﺴﺒﺔ ﻤﻥ ﻭﺘﻘﻠل ﻟﺘﺎﻜل. 1. Introduction Ni-Ti shape memory alloys belong to the group of materials known as "smart functional materials". The outstanding properties exhibited by them are the thermal shape memory effect. The alloy recovers it's programmed shape after heating above a specific temperature A f (austenitic finish temperature) and superelastic (rubber-like) behavior (the alloy recovers its original shape after deformation to tensile strain as high as 8%). These properties are both based on thermo elastic, reversible martensitic transformation [1]. The high temperature austenite phase (with a body centred cubic structure) transforms martensitically upon cooling below an alloy specific temperature to a distorted monoclinic martensite structure. The NiTi shape https://doi.org/10.30684/etj.28.5.11 2412-0758/University of Technology-Iraq, Baghdad, Iraq This is an open access article under the CC BY 4.0 license http://creativecommons.org/licenses/by/4.0
Characterization of Ni-Ti Shape Memory Alloys
Jun 29, 2023
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