Effect of Primary Microstructures during Training Producers on TWSME in NiTi Alloys

تاثير ساختارهاي مارتنزيتي، مارتنزيت+آستنيت و آستنيتي طي تربيت كردن خمشي روي اثر حافظه‌داري دوطرفه آلياژهاي Ni-50.8at% Ti و Ni-49.9at%Ti مطالعه شد. بعلاوه اثر كرنش اوليه، كرنش پلاستيك، سيكل‌هاي تربيت كردن و دماي تربيت كردن روي اثر حافظه‌داري دوطرفه بررسي شد. نمونه‌ها در حالت هاي مارتنزيتي، مارتنزيت+آستنيت و آستنيتي با تغييرشكل خمشي تربيت شدند. با وجود آنكه تعداد سيكل‌هاي تربيت كردن در حالت مارتنزيتي (15-10 سيكل) كمتر از ساير روش‌هاي تربيت كردن (25-15 سيكل) بود، كرنش اوليه در حالت مارتنزيتي (16%) بيش از ساير روش‌ها (12%) بدست آمد. همچنين مشاهده شد كه با افزايش دماي تربيت كردن در حالت آستنيتي، اثر حافظه‌داري دوطرفه افزايش مي‌يابد.

The influence of the martensitic, martensitic+austenitic and austenitic structures during bending training on two-way shape memory effect (TWSME) in Ni-50.8 at %Ti and Ni-49.9 at %Ti alloys has been studied. In addition, the effect of pre-strain, plastic strain, training cycle and training temperature on the TWSME has been investigated. Specimens were trained in martensitic, martensitic+austenitic and austenitic states with bending deformation. The results showed that in martensitic state, TWSME was more than the other states. Although the number of training cycles in martensitic state(10-15 cycle) were less than the other training methods (15-25 cycle), the obtained optimum pre-strain in martensitic state (16%) was more than other training methods (12%). In addition, it was shown that with increasing the training temperature in austenitic state, TWSME decrease.