Evolution of transformation characteristics of shape memory alloys during cyclic loading: transformation temperature hysteresis and residual martensite

Low frequency internal friction of Ti49Ni51 binary and Ti50Ni40Cu10 ternary shape memory alloys has been measured. The effect of solution and aging heat treatments on the damping property was examined. The temperature spectrum of internal friction for TiNi binary alloy consists, in general, of two peaks; one is a transition peak which is associated with the parent-martensite transformation and is rather unstable in a sense that it strongly depends on the frequency and decreases considerably when held at a constant temperature. The other one is a very high peak of the order of 10-2, which appears at around 200K. It appears both on cooling and on heating with no temperature hysteresis, and is very stable. The behavior of the peak is strongly influenced by the heat treatments. The trial of two-stage aging with a purpose of improving the damping capacity has been proved unsatisfactory. TiNiCu has a very high damping, the highest internal friction reaching 0.2, but by quenching from very high temperature, say 1373K, the damping is remarkably lowered. For the realization of high damping the quenching from a certain temperature range around 1173K seems the most preferable condition.

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Martensitic Transformation of High-Entropy and Medium-Entropy Shape Memory Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1016.1802 ◽

2021 ◽

Vol 1016 ◽

pp. 1802-1810

Author(s):

Hiromichi Matsuda ◽

Masayuki Shimojo ◽

Hideyuki Murakami ◽

Yoko Yamabe-Mitarai

Keyword(s):

Solid Solution ◽

High Temperature ◽

Martensitic Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Transformation Temperature ◽

Solid Solution Hardening ◽

Solution Hardening ◽

High Entropy ◽

The One

As new generation of high-temperature shape memory alloys, high-entropy alloys (HEAs) have been attracted for strong solid-solution hardened alloys due to their severe lattice distortion and sluggish diffusion. TiPd is the one potential high-temperature shape memory alloys because of its high martensitic transformation temperature above 500 °C. As constituent elements, Zr expected solid-solution hardening, Pt expected increase of transformation temperature, Au expected keeping transformation temperature, and Co expected not to form harmful phase. By changing the alloy composition slightly, two HEAs and two medium entropy alloys (MEAs) were prepared. Only two MEAs, Ti45Zr5Pd25Pt20Au5, and Ti45Zr5Pd25Pt20Co5 had the martensitic transformation. The perfect recovery was obtained in Ti45Zr5Pd25Pt20Co5 during the repeated thermal cyclic test, training, under 200 MPa. On the other hand, the small irrecoverable strain was remained in Ti45Zr5Pd25Pt20Au5 during the training under 150 MPa because of the small solid-solution hardening effect. It indicates that Ti45Zr5Pd25Pt20Co5 is the one possible HT-SMA working between 342 and 450 °C.

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Influence of Al content on transformation temperature and activation energy of Ti–V–Al high temperature shape memory alloys

Solid State Communications ◽

10.1016/j.ssc.2020.114104 ◽

2021 ◽

Vol 323 ◽

pp. 114104

Author(s):

Öznur Bağ ◽

Semra Ergen ◽

Fikret Yılmaz ◽

Uğur Kölemen

Keyword(s):

Activation Energy ◽

High Temperature ◽

Shape Memory Alloys ◽

Shape Memory ◽

Transformation Temperature ◽

Al Content

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A Macromechanical Constitutive Model of Shape Memory Alloys Under Uniaxial Cyclic Loading

Journal of Mechanics ◽

10.1017/jmech.2012.56 ◽

2012 ◽

Vol 28 (3) ◽

pp. 469-477 ◽

Cited By ~ 4

Author(s):

H. Lei ◽

B. Zhou ◽

Z. Wang ◽

Y. Wang

Keyword(s):

Cyclic Loading ◽

Constitutive Model ◽

Shape Memory Alloys ◽

Mechanical Behavior ◽

Shape Memory ◽

Hysteretic Behavior ◽

Test Results ◽

Model Match ◽

Number Of Cycles ◽

The Relationship

AbstractIn this paper, the thermomechanical behavior of shape memory alloys (SMAs) subjected to uniaxial cyclic loading is investigated. To obtain experimental data, the strain-controlled cyclic loading-unloading tests are conducted at various strain-rates and temperatures. Dislocations slip and deformation twins are considered to be the main reason that causes the unique cyclic mechanical behavior of SMAs. A new variable of shape memory residual factor was introduced, which will tend to zero with the increasing of the number of cycles. Exponential form equations are established to describe the evolution of shape memory residual factor, elastic modulus and critical stress, in which the influence of strain-rate, number of cycles and temperature are taken into account. The relationship between critical stresses and temperature is modified by considering the cycling effect. A macromechanical constitutive model was constructed to predict the cyclic mechanical behavior at constant temperature. Based on the material parameters obtained from test results, the hysteretic behavior of SMAs subjected to isothermal uniaxial cyclic loading is simulated. It is shown that the numerical results of the modified model match well with the test results.

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