Diffusion creep refers to the deformation of crystalline solids by the diffusion of vacancies through their crystal lattice.[1] Diffusion creep results in plastic deformation rather than brittle failure of the material.
Diffusion creep is more sensitive to temperature than other deformation mechanisms. It becomes especially relevant at high homologous temperatures (i.e. within about a tenth of its absolute melting temperature). Diffusion creep is caused by the migration of crystalline defects through the lattice of a crystal such that when a crystal is subjected to a greater degree of compression in one direction relative to another, defects migrate to the crystal faces along the direction of compression, causing a net mass transfer that shortens the crystal in the direction of maximum compression. The migration of defects is in part due to vacancies, whose migration is equal to a net mass transport in the opposite direction.
Crystalline materials are never perfect on a microscale. Some sites of atoms in the crystal lattice can be occupied by point defects, such as "alien" particles or vacancies. Vacancies can actually be thought of as chemical species themselves (or part of a compound species/component) that may then be treated using heterogeneous phase equilibria. The number of vacancies may also be influenced by the number of chemical impurities in the crystal lattice, if such impurities require the formation of vacancies to exist in the lattice.
A vacancy can move through the crystal structure when the neighbouring particle "jumps" in the vacancy, so that the vacancy moves in effect one site in the crystal lattice. Chemical bonds need to be broken and new bonds have to be formed during the process,[2] therefore a certain activation energy is needed. Moving a vacancy through a crystal becomes therefore easier when the temperature is higher.
The most stable state will be when all vacancies are evenly spread through the crystal. This principle follows from Fick's law:
In which Jx stands for the flux ("flow") of vacancies in direction x; Dx is a constant for the material in that direction and Δ Δ --> C / Δ Δ --> x {\displaystyle {\Delta C}/{\Delta x}} is the difference in concentration of vacancies in that direction. The law is valid for all principal directions in (x, y, z)-space, so the x in the formula can be exchanged for y or z. The result will be that they will become evenly distributed over the crystal, which will result in the highest mixing entropy.
When a mechanical stress is applied to the crystal, new vacancies will be created at the sides perpendicular to the direction of the lowest principal stress. The vacancies will start moving in the direction of crystal planes perpendicular to the maximal stress.[3] Current theory holds that the elastic strain in the neighborhood of a defect is smaller toward the axis of greatest differential compression, creating a defect chemical potential gradient (depending upon lattice strain) within the crystal that leads to net accumulation of defects at the faces of maximum compression by diffusion. A flow of vacancies is the same as a flow of particles in the opposite direction. This means a crystalline material can deform under a differential stress, by the flow of vacancies.
Highly mobile chemical components substituting for other species in the lattice can also cause a net differential mass transfer (i.e. segregation) of chemical species inside the crystal itself, often promoting shortening of the rheologically more difficult substance and enhancing deformation.
Diffusion of vacancies through a crystal can happen in a number of ways. When vacancies move through the crystal (in the material sciences often called a "grain"), this is called Nabarro–Herring creep. Another way in which vacancies can move is along the grain boundaries, a mechanism called Coble creep.
When a crystal deforms by diffusion creep to accommodate space problems from simultaneous grain boundary sliding (the movement of whole grains along grain boundaries) this is called granular or superplastic flow.[4] Diffusion creep can also be simultaneous with pressure solution. Pressure solution is, like Coble creep, a mechanism in which material moves along grain boundaries. While in Coble creep the particles move by "dry" diffusion, in pressure solution they move in solution.
Each plastic deformation of a material can be described by a formula in which the strain rate ( ϵ ϵ --> ˙ ˙ --> {\displaystyle {\dot {\epsilon }}} ) depends on the differential stress (σ or σD), the grain size (d) and an activation value in the form of an Arrhenius equation:[5]
ϵ ϵ --> ˙ ˙ --> = A e − − --> Q R T σ σ --> n d m {\displaystyle \!{\dot {\epsilon }}=Ae^{\frac {-Q}{RT}}{\frac {\sigma ^{n}}{d^{m}}}}
In which A is the constant of diffusion, Q the activation energy of the mechanism, R the gas constant and T the absolute temperature (in kelvins). The exponents n and m are values for the sensitivity of the flow to stress and grain size respectively. The values of A, Q, n and m are different for each deformation mechanism. For diffusion creep, the value of n is usually around 1. The value for m can vary between 2 (Nabarro-Herring creep) and 3 (Coble creep). That means Coble creep is more sensitive to grain size of a material: materials with larger grains can deform less easily by Coble creep than materials with small grains.
It is difficult to find clear microscale evidence for diffusion creep in a crystalline material, since few structures have been identified as definite proof. A material that was deformed by diffusion creep can have flattened grains (grains with a so called shape-preferred orientation or SPO). Equidimensional grains with no lattice-preferred orientation (or LPO) can be an indication for superplastic flow.[6] In materials that were deformed under very high temperatures, lobate grain boundaries may be taken as evidence for diffusion creep.[7]
Diffusion creep is a mechanism by which the volume of the crystals can increase. Larger grain sizes can be a sign that diffusion creep was more effective in a crystalline material.
Ancient people mentioned in Chinese histories Not to be confused with Yueshi culture. For Present Yuezi, Yuechi people, see Chechi clan. YuezhiFigures in the embroidered carpets of the Noin-Ula burial site, proposed to be Yuezhis (1st century BC - 1st century AD).[1][2][3][4][5][6][7]The migrations of the Yuezhi through Central Asia, from around 176 BC to 30 ADTotal populationSome 100,000 to 200,000 horse archers, according to the…
United States Department of JusticeNational Security DivisionSeal of the United States Department of Justice National Security DivisionDivision overviewFormedMarch 9, 2005; 18 years ago (2005-03-09)JurisdictionUnited States government agencyHeadquartersRobert F. Kennedy Department of Justice Building950 Pennsylvania Avenue NWWashington, D.C., United StatesDivision executiveMatthew G. Olsen, Assistant Attorney GeneralParent departmentU.S. Department of JusticeWebsiteOfficial web…
此條目须擴充相關主題的現實世界視角內容,如緣由或背景、設計概念、製作及發展過程、評價或影響等。 (2018年3月11日)請根據虚构格式手冊和相关指南來改善這個條目。若條目為電子遊戲類,可根據电子游戏条目指引撰寫。 《蝶之毒華之鎖》是Aromarie公司發行的女性向日本成人遊戲,作品後推出延伸Fan disc《蝶之毒華之鎖 幻想夜話》與廣播劇等改編作品。本表列出這些作品
Salón Internacional del Automóvil MéxicoLocalizaciónPaís México[editar datos en Wikidata] El Salón Internacional del Automóvil México, abreviado como SIAM, es un salón del automóvil, anteriormente con carácter anual, celebrándose en el Centro Banamex ubicado a un lado del Hipódromo de las Américas en la Ciudad de México. Anteriormente se celebraba en el mes de diciembre de cada año. Este evento iba a ser el más corto de vida oficial en los autoshow del mundo, co…
Михайло Михайлович Воскобойников Народився 16 (28) квітня 1873(1873-04-28)Павловськ, Воронезька губернія, Російська імперіяПомер 15 грудня 1942(1942-12-15) (69 років)Кзил-Орда, КазахстанКраїна Російська імперія → СРСРДіяльність зоологAlma mater Московський університетГалузь зоологія, морф…
Indian actress This article is about the Indian actress born in 1982. For the Indian actress born in 1985, see Meenakshi (Malayalam actress). For other people, see Meenakshi (name). MeenakshiMeenakshi posing with a copy of the Thangam magazineBornPinky Sarkar (1982-08-06) 6 August 1982 (age 41)Kolkata, West Bengal, IndiaNationalityIndianOccupationActressYears active2006–2017 Pinky Sarkar (born 6 August 1982[1]) better known as Meenakshi, is an Indian actress, who appears in T…
Bintang PanturaMusim 5Penayangan25 Juni – 17 Agustus 2018JuriNassarInul DaratistaDewi PersikZaskia Gotik[1]Pembawa acaraRamziIrfan HakimGilang DirgaAyu DewiSaluranIndosiarLokasi finalStudio 5 IndosiarPemenangPutri JamilaLagu kemenanganPelangi di MatamuGenredDangdut-PopJuara duaNilah FauzisthaKronologi◀ 2018 ► Bintang Pantura (Musim 5) adalah sebuah ajang pencarian bakat penyanyi dangdut pantura musim kelima dari Bintang Pantura yang ditayangkan di Indosiar. Acara ini mulai digelar …
Rhea ChakrabortyChakraborty pada tahun 2020Lahir1 Juli 1992 (umur 31)Bangalore, Karnataka, IndiaKebangsaanIndianPekerjaanaktrisVJTahun aktif2009—sekarangKota asalBangalore Rhea Chakraborty (lahir 1 Juli 1992) adalah seorang aktris film India.[1][2] Dia memulai sebagai VJ di MTV India.[3] Pada 2013, ia membuat Bollywood debutnya dengan film Mere Dad Ki Maruti disutradarai oleh Ashima Chibber. Rhea Chakraborty dipenjara karna kasus kepemilikan narkoba.[…
Para otros usos de este término, véase Villalpando (desambiguación). Villalpando municipio de España Escudo Puerta de la Villa o de San Andrés. VillalpandoUbicación de Villalpando en España. VillalpandoUbicación de Villalpando en la provincia de Zamora.País España• Com. autónoma Castilla y León• Provincia Zamora• Comarca Tierra de Campos• Partido judicial Villalpando• Municipio Villalpando• Mancom…
CrocodileEpisode Black MirrorPoster promosiNomor episodeEpisode 3SutradaraJohn HillcoatPenulisCharlie BrookerMusikOriginal Score byAtticus RossLeopold RossClaudia SarneTanggal siar29 Desember 2017 (2017-12-29)Durasi59 minutesBintang tamu Andrea Riseborough sebagai Mia Nolan Andrew Gower sebagai Rob Kiran Sonia Sawar sebagai Shazia Akhand Anthony Welsh sebagai Anan Akhand Claire Rushbrook sebagai detektif polisi Joshua James sebagai Gordy Adelle Leonce sebagai Noni Harper-Brown Brian Pettife…
Artikel ini perlu diwikifikasi agar memenuhi standar kualitas Wikipedia. Anda dapat memberikan bantuan berupa penambahan pranala dalam, atau dengan merapikan tata letak dari artikel ini. Untuk keterangan lebih lanjut, klik [tampil] di bagian kanan. Mengganti markah HTML dengan markah wiki bila dimungkinkan. Tambahkan pranala wiki. Bila dirasa perlu, buatlah pautan ke artikel wiki lainnya dengan cara menambahkan [[ dan ]] pada kata yang bersangkutan (lihat WP:LINK untuk keterangan lebih lanjut). …
Дівчинка на тлі перського килима Творець: Врубель Михайло ОлександровичЧас створення: 1886Розміри: 104×68 см.Техніка: полотно, олійні фарбиЖанр: портретЗберігається: Київ, УкраїнаМузей: Київська національна картинна галерея «Дівчинка на тлі перського килима» — станк…
ユリアン・ブラント ドイツ代表でのブラント(2018年)名前ラテン文字 Julian Brandt基本情報国籍 ドイツ生年月日 (1996-05-02) 1996年5月2日(27歳)出身地 ブレーメン身長 185cm体重 83kg選手情報在籍チーム ボルシア・ドルトムントポジション MF / FW背番号 19利き足 右足ユース2001-2009 ボルクフェルト2009-2011 オーバーノイラント2011-2014 ヴォルフスブルククラブ1年 クラブ 出場 (得点)2…
アラン・ヒューストンAllan Houston 2010年のヒューストンウェストチェスター・ニックス GMポジション SG役職 ゼネラルマネージャー基本情報国籍 アメリカ合衆国生年月日 (1971-04-20) 1971年4月20日(52歳)出身地 ケンタッキー州ルイビル身長(現役時) 198cm (6 ft 6 in)体重(現役時) 93kg (205 lb)キャリア情報出身 テネシー大学ドラフト 1993年 11位選手経歴1993-19951995…
Swedish baked potato dish Hasselback potatoes Hasselback potatoes or Potato à la Hasselbacken (Swedish: hasselbackspotatis) are a type of baked potato that is cut about halfway through into thin, fan-like slices. They can be served as a main course,[1] side dish, or canapé.[2][3] Various toppings can be added, such as caraway seeds, paprika, and bread crumbs.[4] Origins Hasselback potatoes may have been created in 1953 by Leif Elisson, a trainee chef at Hasselba…
Typeface designed by William Morris The Golden Type used in a printing of The Nature of Gothic by John Ruskin. The Golden Type is a serif font designed by artist William Morris for his fine book printing project, the Kelmscott Press, in 1890. It is an old-style serif font, based on type designed by engraver and printer Nicolas Jenson in Venice around 1470.[1][2][3] It is named for the Golden Legend, which was intended to be the first book printed using it.[1] The …
Indian writer and linguist Raghunath MurmuPortrait of Raghunath MurmuNative nameᱨᱚᱜᱷᱩᱱᱟᱛᱷ ᱢᱩᱨᱢᱩBorn5 May 1905Mayurbhanj State, British India (present-day Mayurbhanj, Odisha, India)Died1 February 1982(1982-02-01) (aged 76)OccupationIdeologist, playwright, and writerNationalityIndianSubjectOl Chiki alphabet Raghunath Murmu (5 May 1905[1][2] – 1 February 1982)[3] was an Indian Santali writer and educator. He developed the Ol Chiki script fo…
Species of butterfly Aeria eurimedia Scientific classification Domain: Eukaryota Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Lepidoptera Family: Nymphalidae Genus: Aeria Species: A. eurimedia Binomial name Aeria eurimedia(Cramer, [1777])[1] Synonyms List Papilio eurimedia Cramer, [1777] Ithomia eurimedia var. negricola C. & R. Felder, 1862 Aeria agna Godman & Salvin, [1879] Ithomia indola Doubleday, [1845] Ithomia agna Doubleday, 1847 Aeria pacifica Godman &am…
National flag As a result of the Syrian Civil War since 2011, there are at least two flags used to represent Syria, used by different factions in the war.[1] The incumbent government of the Syrian Arab Republic led by the Ba'ath Party uses the red-white-black tricolour originally used by the United Arab Republic, while Syrian opposition factions such as the Syrian National Coalition use the green-white-black tricolour known as the ''Independence flag'', first used by Mandatory Syria. Fla…
Hospital in Pembroke Place, LiverpoolLiverpool Royal InfirmaryMain building on Pembroke PlaceLocation in LiverpoolShow map of LiverpoolLocation in MerseysideShow map of MerseysideGeographyLocationPembroke Place, LiverpoolCoordinates53°24′32″N 2°58′05″W / 53.409°N 2.968°W / 53.409; -2.968OrganisationCare systemPublic NHSTypeTeachingAffiliated universityUniversity of LiverpoolHistoryOpened1743Closed1978 The Liverpool Royal Infirmary was a hospital in Pembroke Pl…
Lokasi Pengunjung: 18.118.26.217