词条 | Invar |
释义 |
It was invented in 1896 by Swiss physicist Charles Édouard Guillaume. He received the Nobel Prize in Physics in 1920 for this discovery, which enabled improvements in scientific instruments.[2] PropertiesLike other nickel/iron compositions, Invar is a solid solution; that is, it is a single-phase alloy, consisting of around 36% nickel and 64% iron.[3] Common grades of Invar have a coefficient of thermal expansion (denoted α, and measured between 20 °C and 100 °C) of about 1.2 × 10−6 K−1 (1.2 ppm/°C), while ordinary steels have values of around 11–15 ppm. Extra-pure grades (<0.1% Co) can readily produce values as low as 0.62–0.65 ppm/°C. Some formulations display negative thermal expansion (NTE) characteristics. Though it displays high dimensional stability over a range of temperatures, it does have a propensity to creep. ApplicationsInvar is used where high dimensional stability is required, such as precision instruments, clocks, seismic creep gauges, television shadow-mask frames,[4] valves in engines, antimagnetic watches, and large aerostructure molds. In land surveying, when first-order (high-precision) elevation leveling is to be performed, the level staff (leveling rod) used is made of Invar, instead of wood, fiberglass, or other metals.{{citation needed|date=August 2018}} Invar struts were used in some pistons to limit their thermal expansion inside their cylinders.[5] In the manufacture of large composite material structures for aerospace carbon fibre layup molds, invar is used to facilitate the manufacture of parts to extremely tight tolerances.[6] VariationsThere are variations of the original Invar material that have slightly different coefficient of thermal expansion such as:
Explanation of anomalous propertiesA detailed explanation of Invar's anomalously low CTE has proven elusive for physicists. All the iron-rich face-centered cubic Fe–Ni alloys show Invar anomalies in their measured thermal and magnetic properties that evolve continuously in intensity with varying alloy composition. Scientists had once proposed that Invar's behavior was a direct consequence of a high-magnetic-moment to low-magnetic-moment transition occurring in the face centered cubic Fe–Ni series (and that gives rise to the mineral antitaenite); however, this theory was proven incorrect.[7] Instead, it appears that the low-moment/high-moment transition is preceded by a high-magnetic-moment frustrated ferromagnetic state in which the Fe–Fe magnetic exchange bonds have a large magneto-volume effect of the right sign and magnitude to create the observed thermal expansion anomaly.[8] See also
References1. ^{{cite book | last = Davis | first = Joseph R. | title = Alloying: Understanding the Basics | publisher = ASM International | pages = 587–589| isbn = 0-87170-744-6 }} 2. ^{{cite web |title=The Nobel Prize in Physics 1920 |url=http://nobelprize.org/nobel_prizes/physics/laureates/1920/ |work=nobelprize.org |publisher=The Nobel Foundation |accessdate=20 March 2011 |quote=The Nobel Prize in Physics 1920 was awarded to Charles Edouard Guillaume "in recognition of the service he has rendered to precision measurements in Physics by his discovery of anomalies in nickel steel alloys".}} 3. ^{{Cite web|url=https://www.vdm-metals.com/fileadmin/user_upload/Downloads/Data_Sheets/Data_Sheet_VDM_Alloy_36.pdf|title=Material Data Sheet Alloy 36|last=|first=|date=|website=|access-date=24 November 2017}} 4. ^{{cite web |title=Nickel & Its Uses |publisher=Nickel Institute |work=Nickel Magazine |date=3 May 2005 |url=http://www.nickelinstitute.org/index.cfm/ci_id/12313.htm |accessdate=20 March 2011 |deadurl=yes |archiveurl=https://web.archive.org/web/20101219005643/http://www.nickelinstitute.org/index.cfm/ci_id/12313.htm |archivedate=19 December 2010 |df=dmy-all }} 5. ^{{cite book|title=Internal combustion engines illustrated|year=1947|publisher=Odhams Press Limited|location=Long Acre, London|page=85}} 6. ^[https://www.aero-mag.com/tooling-mould-die/ Tooling to mould and die for!], Mike Richardson, Aerospace Manufacturing, 6 April 2018, accessed 10 April 2018. 7. ^{{cite journal |author1=K. Lagarec |author2=D.G. Rancourt |author3=S.K. Bose |author4=B. Sanyal |author5=R.A. Dunlap |url=http://fizz.phys.dal.ca/~dunlap/index_files/index_files/journal/c210_lagarec.pdf |title=Observation of a composition-controlled high-moment/low-moment transition in the face centered cubic Fe–Ni system: Invar effect is an expansion, not a contraction |journal=Journal of Magnetism and Magnetic Materials |volume=236 |year=2001 |pages=107–130 |doi=10.1016/S0304-8853(01)00449-8 |bibcode=2001JMMM..236..107L |deadurl=yes |archiveurl=https://web.archive.org/web/20120425145000/http://fizz.phys.dal.ca/~dunlap/index_files/index_files/journal/c210_lagarec.pdf |archivedate=25 April 2012 |df=dmy-all }} 8. ^{{cite journal|author1=D.G. Rancourt |author2=M.-Z. Dang |title= Relation between anomalous magneto-volume behaviour and magnetic frustration in Invar alloys|journal=Physical Review B|volume= 54|issue= 17|year=1996|pages= 12225–12231|doi=10.1103/PhysRevB.54.12225|bibcode=1996PhRvB..5412225R}} External links
4 : Ferrous alloys|Nickel alloys|Named alloys|Surveying instruments |
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