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Monday, September 22, 2008
Abstract ID#: 20366
Password: 834182
Title: SME and TWSME Study in Ti-Ni Alloy after Strain Aging
Session Selection: SMA Properties and Characterizations
Presentation Format: Oral
Lead Presenter's E-mail Address: dreams_sea@mail.ru
Summary: This paper focuses on the optimization of shape memory effect (SME) training parameters bringing maximum one-way and two-way recovery strain. The joint effect of isothermal annealing at 430 deg.C after Low-Temperature Thermomechanical Treatment (LTMT) and external training parameters on functional properties of Ti-50.7%Ni alloy is studied. The homogenizing annealing at 700 deg.C, 20 min is chosen as a reference heat treatment (RHT). Under experiment procedure, the bending loading mode, strain state, loading value and loading time were varied. Increasing of strain aging time from 10 min to 10 hr affects characteristic temperatures As and Af after aging and RHT, however, in the case of LTMT the As - Af temperature range is significantly wider than after RHT. The TEM and X-ray studies testify that it is caused by two factors: heterogeneity of nano-size subgrain structure and nano-phase Ti3Ni4 precipitates. The evolution of SME and two-way TWSME parameters is studied as well. The recovery strain er and TWSME amplitude eTW increase with aging time. Variation of loading time is effective for eTW regulation; the achievement of required TWSME value is possible after minimum number of training cycles owing to exposure time increasing in a constrained condition. The loading mode and constraining strain et strongly affect all studied SME and TWSME parameters. Variation of training parameters enables additional precise regulation of final functional properties. The obtained results can be used for development elements functioning under TWSME realization.
Password: 834182
Title: SME and TWSME Study in Ti-Ni Alloy after Strain Aging
Session Selection: SMA Properties and Characterizations
Presentation Format: Oral
Lead Presenter's E-mail Address: dreams_sea@mail.ru
Summary: This paper focuses on the optimization of shape memory effect (SME) training parameters bringing maximum one-way and two-way recovery strain. The joint effect of isothermal annealing at 430 deg.C after Low-Temperature Thermomechanical Treatment (LTMT) and external training parameters on functional properties of Ti-50.7%Ni alloy is studied. The homogenizing annealing at 700 deg.C, 20 min is chosen as a reference heat treatment (RHT). Under experiment procedure, the bending loading mode, strain state, loading value and loading time were varied. Increasing of strain aging time from 10 min to 10 hr affects characteristic temperatures As and Af after aging and RHT, however, in the case of LTMT the As - Af temperature range is significantly wider than after RHT. The TEM and X-ray studies testify that it is caused by two factors: heterogeneity of nano-size subgrain structure and nano-phase Ti3Ni4 precipitates. The evolution of SME and two-way TWSME parameters is studied as well. The recovery strain er and TWSME amplitude eTW increase with aging time. Variation of loading time is effective for eTW regulation; the achievement of required TWSME value is possible after minimum number of training cycles owing to exposure time increasing in a constrained condition. The loading mode and constraining strain et strongly affect all studied SME and TWSME parameters. Variation of training parameters enables additional precise regulation of final functional properties. The obtained results can be used for development elements functioning under TWSME realization.