scholarly journals On the functional degradation of binary titanium–tantalum high-temperature shape memory alloys — A new concept for fatigue life extension

2014 ◽  
Vol 07 (04) ◽  
pp. 1450042 ◽  
Author(s):  
T. Niendorf ◽  
P. Krooß ◽  
E. Batyrsina ◽  
A. Paulsen ◽  
J. Frenzel ◽  
...  

High-temperature shape memory alloys are promising candidates for actuator applications at elevated temperatures. Ternary nickel–titanium-based alloys either contain noble metals which are very expensive, or suffer from poor workability. Titanium–tantalum shape memory alloys represent a promising alternative if one can avoid the cyclic degradation due to the formation of the omega phase. The current study investigates the functional fatigue behavior of Ti – Ta and introduces a new concept providing for pronounced fatigue life extension.

2015 ◽  
Vol 08 (06) ◽  
pp. 1550062 ◽  
Author(s):  
T. Niendorf ◽  
P. Krooß ◽  
C. Somsen ◽  
R. Rynko ◽  
A. Paulsen ◽  
...  

Titanium–tantalum shape memory alloys (SMAs) are promising candidates for actuator applications at elevated temperatures. They may even succeed in substituting ternary nickel–titanium high temperature SMAs, which are either extremely expensive or difficult to form. However, titanium–tantalum alloys show rapid functional and structural degradation under cyclic thermo-mechanical loading. The current work reveals that degradation is not only governed by the evolution of the ω-phase. Dislocation processes and chemical decomposition of the matrix at grain boundaries also play a major role.


1991 ◽  
Vol 246 ◽  
Author(s):  
R. Kainuma ◽  
H. Nakano ◽  
K. Oikawa ◽  
K. Ishida ◽  
T. Nishizawa

AbstractAn attempt to develop a new type of high temperature shape memory alloys based on the Ni-Al system has been made through microstructural control. Addition of Fe or Mn to the binary Ni-Al alloy results in the formation of a ductile fcc phase in an extremely brittle P matrix phase, leading to an improvement in its ductility. These ductile alloys with β + γ two-phase structure in the Ni-Al-Fe, Ni-Al-Mn and Ni-Al-Mn-Fe systems exhibit a shape memory effect due to a thermoelastic martensitic transformation in the temperature range between -100°C and 700°C; besides, the transformation temperatures are easily controlled by annealing at an appropriate temperature. These alloys are expected to be a new group of shape memory alloys which operate at elevated temperatures.


Author(s):  
H Onat Tugrul ◽  
Hasan H Saygili ◽  
Benat Kockar

The cyclic stability and the fatigue life of NiTiHf alloys are very important for their functionality at high temperatures. The previous studies have shown that the increase in Upper Cycle Temperature (UCT) and the magnitude of applied stress decreased the cyclic stability and fatigue life of NiTiHf high temperature shape memory alloys due to plasticity with dislocation formation at high temperature. On the other hand, this study was dedicated to the effect of limited actuation strain against the applied constant stress to the functional fatigue life and the possible damage mechanism such as dislocation and crack formation. Strain limitation led to observe insignificant amount of accumulated irrecoverable strain but significant amount of crack formation such that the reason of the failure of Ni50.3Ti29.7Hf20 (at%) alloy was found to be the crack formation instead of dislocation accumulation.


2020 ◽  
Vol 794 ◽  
pp. 139857 ◽  
Author(s):  
O. Karakoc ◽  
K.C. Atli ◽  
A. Evirgen ◽  
J. Pons ◽  
R. Santamarta ◽  
...  

Metals ◽  
2017 ◽  
Vol 7 (11) ◽  
pp. 511 ◽  
Author(s):  
Matthew Carl ◽  
Jesse Smith ◽  
Brian Van Doren ◽  
Marcus Young

Sign in / Sign up

Export Citation Format

Share Document