how to test existence of martensite stabilization in shape memory alloys
Which shape memory alloy is this? Ni-based? If it is Ni based, this may be due to the B19' phase. You may read some papers regarding austenite - R phase - B19' phase transformations. The existence can probably be observed with TEM.
thank you very much sir, i had doubt on Copper based shape memory alloys.
You are welcome, unfortunately I have no information on Cu effect. I recommend you "Shape memory materials" book by Otsuka and Wayman. Personally, it is the best book on shape memory materials in the literature.
to develop a new material for actuator, based on thermal induced transformation. does it requires to satisfy both the shape memory and superelasticity property? or shape memory effect is enough?
What temperature do you need to reach approximately? What loading scenarios will be exerted on shape memory material?
Have a look at the paper, "Aging Response to Microstructure and Properties of Ferromagnetic Shape Memory Alloys", Advanced Materials Research Vol. 326 (2011) pp 81-87.
Dear Bala,
Martensite stabilization means that martensite once formed during the forward transformation (during cooling) does not undergo the reverse transformation to austenite (during heating), so it becomes much more stable and it is said that martensite is stabilized. In general, any process shifting to high temperature the reverse transformation temperatures As and Af, could be considered as an stabilization of the martensite.
This is due to several different processes linked to the dificulty of moving back the interfaces of martensite because of the pinning by vacancies (for instance), or because an intrinsic decrease of the free energy (due to atomic ordering for instance).
These mechanisms can produce an strong stabilization effect on Cu-Based SMA, for which there is a lot of information related to stabilization of martensite, but there have been scarcely reported for Ti-Ni alloys.
To avoid stabilization of the martensite, the usual procedure is to perform thermal treatments in order to avoid the migration of vacancies (during or after quenching) towards the martensite interfaces. For instance by step quenching. Another point is to promote atomic ordering in austenite, previously to transform to martensite, in order to avoid further evolution of the transformation temperatures. This is done tipically by an aging treatment.
You may give a look to the two papers I send you here attached, in which you can find also some bibliography on this field.
The complete understanding of stabilization of martensite is a bit more complex, but I hope that this could be useful for you.
Jose sir Thank you Very much for Your answer. now i got an idea abt that.