scholarly journals High-Temperature Nano-Indentation Creep of Reduced Activity High Entropy Alloys Based on 4-5-6 Elemental Palette

Entropy ◽  
2020 ◽  
Vol 22 (2) ◽  
pp. 230 ◽  
Author(s):  
Maryam Sadeghilaridjani ◽  
Saideep Muskeri ◽  
Mayur Pole ◽  
Sundeep Mukherjee
Keyword(s):  
Stress Exponent ◽  
Creep Resistance ◽  
Nuclear Reactors ◽  
Indentation Creep ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Nano Indentation ◽  
Creep Stress ◽  
Plastic Deformation Behavior ◽  
Reduced Activity

There is a strong demand for materials with inherently high creep resistance in the harsh environment of next-generation nuclear reactors. High entropy alloys have drawn intense attention in this regard due to their excellent elevated temperature properties and irradiation resistance. Here, the time-dependent plastic deformation behavior of two refractory high entropy alloys was investigated, namely HfTaTiVZr and TaTiVWZr. These alloys are based on reduced activity metals from the 4-5-6 elemental palette that would allow easy post-service recycling after use in nuclear reactors. The creep behavior was investigated using nano-indentation over the temperature range of 298 K to 573 K under static and dynamic loads up to 5 N. Creep stress exponent for HfTaTiVZr and TaTiVWZr was found to be in the range of 20–140 and the activation volume was ~16–20b3, indicating dislocation dominated mechanism. The stress exponent increased with increasing indentation depth due to a higher density of dislocations and their entanglement at larger depth and the exponent decreased with increasing temperature due to thermally activated dislocations. Smaller creep displacement and higher activation energy for the two high entropy alloys indicate superior creep resistance compared to refractory pure metals like tungsten.

scholarly journals High-Temperature Nano-Indentation Creep Behavior of Multi-Principal Element Alloys under Static and Dynamic Loads

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 250 ◽  
Author(s):  
Maryam Sadeghilaridjani ◽  
Sundeep Mukherjee
Keyword(s):  
Stress Exponent ◽  
Dynamic Loads ◽  
Dislocation Creep ◽  
Indentation Creep ◽  
Principal Element ◽  
Dislocation Glide ◽  
Nano Indentation ◽  
Plastic Deformation Behavior ◽  
Structural Applications ◽  
Static And Dynamic Loads

Creep is a serious concern reducing the efficiency and service life of components in various structural applications. Multi-principal element alloys are attractive as a new generation of structural materials due to their desirable elevated temperature mechanical properties. Here, time-dependent plastic deformation behavior of two multi-principal element alloys, CoCrNi and CoCrFeMnNi, was investigated using nano-indentation technique over the temperature range of 298 K to 573 K under static and dynamic loads with applied load up to 1000 mN. The stress exponent was determined to be in the range of 15 to 135 indicating dislocation creep as the dominant mechanism. The activation volume was ~25b3 for both CoCrNi and CoCrFeMnNi alloys, which is in the range indicating dislocation glide. The stress exponent increased with increasing indentation depth due to higher density and entanglement of dislocations, and decreased with increasing temperature owing to thermally activated dislocations. The results for the two multi-principal element alloys were compared with pure Ni. CoCrNi showed the smallest creep displacement and the highest activation energy among the three systems studied indicating its superior creep resistance.

Measurement of Press Creep Stress Exponent of ZM6 Alloy at Room Temperature

2007 ◽  
Vol 546-549 ◽  
pp. 509-511
Author(s):  
Ying Ying Zhong ◽  
Shu Fang Xu ◽  
Xin Ming Zhang ◽  
Tian Cai Guo ◽  
Yun Lai Deng
Keyword(s):  
Strain Rate ◽  
Linear Relationship ◽  
Stress Exponent ◽  
Room Temperature ◽  
Constant Load ◽  
Nano Indentation ◽  
Indentation Technique ◽  
Creep Stress ◽  
Creep Stress Exponent ◽  
Relationship Of

Nano-indentation technique was used to survey creep stress exponent of ZM6 (Mg-2.8Nd-0.7Zn-0.6Zr) alloy at room temperature. The results showed that average press creep stress exponent of ZM6 alloy was about 89.75, and independent of strain rate and hardness, which has been verified by linear relationship of the double logarithmic plots between strain rate ( ε& ) and hardness (H ) measured by a nano-indentation equipment with constant load of 500mN.

scholarly journals Indentation creep of a Ti-based metallic glass

2009 ◽  
Vol 24 (3) ◽  
pp. 993-997 ◽  
Author(s):  
Y.J. Huang ◽  
Y.L. Chiu ◽  
J. Shen ◽  
J.J.J. Chen ◽  
J.F. Sun
Keyword(s):  
Metallic Glass ◽  
Size Effect ◽  
Stress Exponent ◽  
Deformation Behavior ◽  
Room Temperature ◽  
Bulk Sample ◽  
Indentation Creep ◽  
Indentation Size ◽  
Plastic Deformation Behavior ◽  
Measured Stress

In this work, the time-dependent plastic deformation behavior of Ti40Zr25Ni3Cu12Be20 bulk and ribbon metallic glass alloys was investigated using a nanoindentation technique at room temperature with the applied load ranging from 5 to 100 mN. The stress exponent n, defined as, has been derived as a measure of the creep resistance. It was found that the measured stress exponent increases rapidly with increasing indentation size, exhibiting a positive size effect. The size effect on the stress exponent n obtained from the bulk sample is more pronounced than that obtained from the ribbon sample. The deformation mechanism involved will be discussed.

scholarly journals Ambient-Temperature Indentation Creep of Shape Memory NiTi Alloys: Additively Manufactured versus Cast

2021 ◽  
Vol 5 (3) ◽  
pp. 87
Author(s):  
Md. Minhazul Islam ◽  
Parisa Bayati ◽  
Mohammadreza Nematollahi ◽  
Ahmadreza Jahadakbar ◽  
Mohammad Elahinia ◽  
...  
Keyword(s):  
Size Effect ◽  
Ambient Temperature ◽  
Stress Exponent ◽  
Indentation Size Effect ◽  
Indentation Creep ◽  
Indentation Size ◽  
Niti Alloys ◽  
Creep Stress ◽  
Heat Treated ◽  
Creep Stress Exponent

In this study, depth-sensing indentation creep response of cast and additively manufactured (laser powder bed fusion) NiTi alloys in heat-treated conditions have been investigated at ambient temperature. Indentation creep tests were evaluated with the help of a dual-stage approach comprising a loading segment with a subsequent constant load-holding stage and an unloading phase afterward. The investigation was carried out at a maximum load of 50 mN along with a holding time of 600 s. Different creep parameters comprising indentation creep displacement, creep strain rate, creep stress exponent as well as the indentation size effect have been analyzed quantitatively for the employed materials. In addition, microstructural analysis has been performed to ascertain the processing–microstructure–creep property correlations. A substantial indentation size effect was seen for both cast and printed NiTi samples in heat-treated conditions. According to the creep stress exponent measurements, the dominant mechanism of rate-dependent plastic deformation for all NiTi samples at ambient temperature is attributed to the dislocation movement (i.e., glide/climb). The outcome of this investigation will act as a framework to understand the underlying mechanisms of ambient-temperature indentation creep of the cast and printed NiTi alloy in conjunction with heat-treated conditions.

Unusual plastic deformation behavior of nanotwinned Cu/high entropy alloy FeCoCrNi nanolaminates

Nanoscale ◽  
2019 ◽  
Vol 11 (23) ◽  
pp. 11340-11350 ◽  
Author(s):  
Y. F. Zhao ◽  
J. Y. Zhang ◽  
Y. Q. Wang ◽  
K. Wu ◽  
G. Liu ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Deformation Behavior ◽  
Dominant Role ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Popular Belief ◽  
Soft Phase ◽  
High Entropy ◽  
Plastic Deformation Behavior

Contrary to the popular belief that the soft phase in bimetal multilayers plays the dominant role in plastic deformation, the hard FeCoCrNi high entropy alloys (HEA) phase makes more contribution to the deformation of Cu/HEA nanolaminates.

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