In materials science, the yield strength anomaly refers to materials wherein the yield strength (i.e., the stress necessary to initiate plastic yielding) increases with temperature.[1][2][3] For the majority of materials, the yield strength decreases with increasing temperature. In metals, this decrease in yield strength is due to the thermal activation of dislocation motion, resulting in easier plastic deformation at higher temperatures.[4]
In some cases, a yield strength anomaly refers to a decrease in the ductility of a material with increasing temperature, which is also opposite the trend in the majority of materials. Anomalies in ductility can be more clear, as an anomalous effect on yield strength can be obscured by its typical decrease with temperature.[5] In concert with yield strength or ductility anomalies, some materials demonstrate extrema in other temperature dependent properties, such as a minimum in ultrasonic damping, or a maximum in electrical conductivity.[6]
The yield strength anomaly in β-brass was one of the earliest discoveries such a phenomenon,[7] and several other ordered intermetallic alloys demonstrate this effect. Precipitation-hardened superalloys exhibit a yield strength anomaly over a considerable temperature range. For these materials, the yield strength shows little variation between room temperature and several hundred degrees Celsius. Eventually, a maximum yield strength is reached. For even higher temperatures, the yield strength decreases and, eventually, drops to zero when reaching the melting temperature, where the solid material transforms into a liquid. For ordered intermetallics, the temperature of the yield strength peak is roughly 50% of the absolute melting temperature.[8]
- ^ Liu, J.B.; Johnson, D.D.; Smirnov, A.V. (24 May 2005), "Predicting yield-stress anomalies in L12 alloys: Ni3Ge–Fe3Ge pseudo-binaries", Acta Materialia, 53 (13): 3601–3612, Bibcode:2005AcMat..53.3601L, doi:10.1016/j.actamat.2005.04.011
- ^ Wua, D.; Baker, I.; Munroe, P.R.; George, E.P. (February 2007), "The yield strength anomaly of single-slip-oriented Fe–Al single crystals", Intermetallics, 15 (2): 103–107, doi:10.1016/j.intermet.2006.03.007
- ^ Gornostyrev, Yu. N.; A. F. Maksyutov; O. Yu. Kontsevoi; A. J. Freeman; M. I. Katsnelson; A. V. Trefilov (3 March 2003), "Negative yield stress temperature anomaly and structural stability of Pt3Al", American Physical Society March Meeting 2003, vol. 2003, American Physical Society, pp. D17.009, Bibcode:2003APS..MARD17009G
- ^ Smallman, R. E. (4 September 2013). Modern physical metallurgy. Ngan, A. H. W. (Eighth ed.). Oxford. ISBN 978-0-08-098223-6. OCLC 858948359.
{{cite book}}: CS1 maint: location missing publisher (link) - ^ Han, F. F.; Zhou, B. M.; Huang, H. F.; Leng, B.; Lu, Y. L.; Dong, J. S.; Li, Z. J.; Zhou, X. T. (2016-10-01). "The tensile behavior of GH3535 superalloy at elevated temperature". Materials Chemistry and Physics. 182: 22–31. doi:10.1016/j.matchemphys.2016.07.001. ISSN 0254-0584.
- ^ Chu, Zhaokuang; Yu, Jinjiang; Sun, Xiaofeng; Guan, Hengrong; Hu, Zhuangqi (2010-05-15). "Tensile property and deformation behavior of a directionally solidified Ni-base superalloy". Materials Science and Engineering: A. 527 (12): 3010–3014. doi:10.1016/j.msea.2010.01.051. ISSN 0921-5093.
- ^ Ardley, G. W.; Cottrell, Alan Howard; Mott, Nevill Francis (1953-09-22). "Yield points in brass crystals". Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences. 219 (1138): 328–340. Bibcode:1953RSPSA.219..328A. doi:10.1098/rspa.1953.0150. S2CID 137118204.
- ^ George, E.P.; Baker, I. (1998). "A model for the yield strength anomaly of Fe—Al". Philosophical Magazine A. 77 (3): 737–750. Bibcode:1998PMagA..77..737G. doi:10.1080/01418619808224080.