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

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.

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Grain Size Effect on the Creep Behavior of Monolithic MoSi2

MRS Proceedings ◽

10.1557/proc-364-1053 ◽

1994 ◽

Vol 364 ◽

Cited By ~ 4

Author(s):

C.R. Feng ◽

K. Sadananda

Keyword(s):

Grain Size ◽

Size Effect ◽

Stress Exponent ◽

Creep Behavior ◽

Molybdenum Disilicide ◽

Grain Size Effect ◽

Stress Range ◽

Creep Stress ◽

Creep Stress Exponent

AbstractThe grain size effect on the creep behavior of hot-pressed monolithic molybdenum disilicide was investigated at 1200°C in a 19–255 MPa stress range. The creep-stress exponent, n, increased from 1 at low stresses to 4 at high stresses. The grain size exponent, p, varied from 0, to 3.5 and to 8 depending on the grain size, the creep-stress exponent, and creep history.

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Indentation creep of a Ti-based metallic glass

Journal of Materials Research ◽

10.1557/jmr.2009.0106 ◽

2009 ◽

Vol 24 (3) ◽

pp. 993-997 ◽

Cited By ~ 24

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.

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Indentation size effect of stress exponent and hardness in homogeneous duplex eutectic 80Au/20Sn

Materials Letters ◽

10.1016/j.matlet.2014.01.066 ◽

2014 ◽

Vol 120 ◽

pp. 151-154 ◽

Cited By ~ 9

Author(s):

Wensheng Liu ◽

Yikai Wang ◽

Yunzhu Ma ◽

Yufeng Huang ◽

Ya Tang ◽

...

Keyword(s):

Size Effect ◽

Stress Exponent ◽

Indentation Size Effect ◽

Indentation Size

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Vickers hardness indentation size effect in selective laser melted MS1 maraging steel

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406219892301 ◽

2019 ◽

pp. 095440621989230 ◽

Cited By ~ 1

Author(s):

Sebastian Balos ◽

Dragan Rajnovic ◽

Leposava Sidjanin ◽

Olivera Eric Cekic ◽

Slobodan Moraca ◽

...

Keyword(s):

Size Effect ◽

Cross Sections ◽

Vickers Hardness ◽

Indentation Size Effect ◽

Full Range ◽

Indentation Size ◽

Load Dependence ◽

Proportional Specimen Resistance ◽

Heat Treated ◽

Correlation Factors

In this paper, selective laser melting fabricated specimens in non-heat-treated and heat-treated conditions were subjected to Vickers microhardness testing, by using a full range of loadings: 10, 25, 50, 100, 200, 300, 500, and 1000 g. Microhardness of longitudinal sections and cross-sections were correlated and the obtained values were plotted against loadings and indentation size effect was studied, in order to find the optimal loading range, that gives the material true microhardness, or load-independent hardness. The load dependence of the measured Vickers hardness values was described quantitatively through the application of the Meyer’s law, proportional specimen resistance, and the modified proportional specimen resistance model. It was found that the microhardness rises as the loading is higher, causing a reversed indentation size effect, clearly indicating the range of true hardnesses of the tested material. Also, proportional specimen resistance and modified proportional specimen resistance models were found to have the highest correlation factors indicating their higher adequacy compared to Meyer’s prediction model.

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Investigation of the mechanism of the indentation size effect for titanium

Mechanical Engineering Journal ◽

10.1299/mej.18-00545 ◽

2019 ◽

Vol 6 (2) ◽

pp. 18-00545-18-00545

Author(s):

Shota HASUNUMA ◽

Hirohisa MIYAZAKI ◽

Takeshi OGAWA

Keyword(s):

Size Effect ◽

Indentation Size Effect ◽

Indentation Size

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Study of the interaction between the indentation size effect and Hall–Petch effect with spherical indenters on annealed polycrystalline copper

Journal of Physics D Applied Physics ◽

10.1088/0022-3727/41/7/074006 ◽

2008 ◽

Vol 41 (7) ◽

pp. 074006 ◽

Cited By ~ 52

Author(s):

X D Hou ◽

A J Bushby ◽

N M Jennett

Keyword(s):

Size Effect ◽

Indentation Size Effect ◽

Polycrystalline Copper ◽

Indentation Size

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Cracking and the Indentation Size Effect for Knoop Hardness of Glasses

Journal of the American Ceramic Society ◽

10.1111/j.1151-2916.2003.tb03319.x ◽

2003 ◽

Vol 86 (3) ◽

pp. 441-448 ◽

Cited By ~ 43

Author(s):

George D. Quinn ◽

Patrice Green ◽

Kang Xu

Keyword(s):

Size Effect ◽

Indentation Size Effect ◽

Knoop Hardness ◽

Indentation Size

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Indentation size effect of cortical bones submitted to different soft tissue removals

Journal of the Mechanical Behavior of Biomedical Materials ◽

10.1016/j.jmbbm.2013.02.011 ◽

2013 ◽

Vol 20 ◽

pp. 338-346 ◽

Cited By ~ 4

Author(s):

A. Bandini ◽

D. Chicot ◽

P. Berry ◽

X. Decoopman ◽

A. Pertuz ◽

...

Keyword(s):

Soft Tissue ◽

Size Effect ◽

Indentation Size Effect ◽

Indentation Size

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Further analysis of the size effect in indentation hardness tests of some metals

Journal of Materials Research ◽

10.1557/jmr.1995.2908 ◽

1995 ◽

Vol 10 (11) ◽

pp. 2908-2915 ◽

Cited By ~ 72

Author(s):

M. Atkinson

Keyword(s):

Size Effect ◽

Strain Hardening ◽

Indentation Size Effect ◽

Plastic Hinge ◽

Small Scale ◽

Indentation Hardness ◽

Vickers Indentation ◽

Indentation Size ◽

Hardness Tests ◽

Indentation Tests

The variation of apparent hardness observed in previously reported Vickers indentation tests of metals is reexamined. Common deseriptions of the effect are shown to be inaccurate: the variation of apparent hardness is monotonic but not simple. The effect is consistent with varying size of a previously postulated “plastic hinge” at the perimeter of the indent. This complexity confers uncertainty on the estimation of characteristic macrohardness from small scale tests. Association of the indentation size effect with friction and with strain hardening is confirmed.

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