Hlau melting yog ib qho txheej txheem thermodynamic uas cov siv lead ua lattice ntawm cov hlau puas thiab nws dhau los ntawm cov khoom hauv lub xeev mus rau lub xeev ua kua.
Melting point of metals - qhov taw qhia ntawm qhov kub thiab txias ntawm cov hlau rhuab, thaum ncav cuag cov txheej txheem ntawm theem hloov (melting) pib. Cov txheej txheem nws tus kheej yog qhov thim rov qab ntawm crystallization thiab yog inextricably txuas nrog nws. Ua kom yaj hlau? nws yuav tsum tau rhuab siv ib qho hluav taws xob sab nraud rau lub melting point, thiab tom qab ntawd txuas ntxiv muab cov cua sov kom kov yeej lub zog ntawm cov theem hloov. Qhov tseeb yog tias tus nqi ntawm qhov melting point ntawm hlau qhia qhov kub ntawm cov khoom yuav nyob rau hauv theem equilibrium, nyob rau hauv ciam teb ntawm cov kua thiab cov khoom. Ntawm qhov kub no, cov hlau ntshiab tuaj yeem nyob ib txhij hauv ob qho tib si khoom thiab kua. Txhawm rau ua kom tiav cov txheej txheem melting, nws yog ib qho tsim nyog yuav tsum overheat cov hlau me ntsis saum toj no qhov sib npaug ntawm qhov ntsuas kub kom thiaj li muaj peev xwm ua tau zoo thermodynamic. Muab ib hom kev txhawb nqa rau tus txheej txheem.
Melting point of metalsyog tas mus li rau cov khoom ntshiab. Lub xub ntiag ntawm impurities yuav hloov lub peev xwm sib npaug ntawm ib qho kev coj los yog lwm qhov. Qhov no yog vim hais tias cov hlau nrog impurities tsim ib tug sib txawv siv lead ua lattice, thiab kev sib cuam tshuam rog ntawm atoms nyob rau hauv lawv yuav txawv ntawm cov tam sim no nyob rau hauv cov ntaub ntawv ntshiab, nyob ntawm qhov melting point, hlau muab faib ua fusible (txog 600 ° C, xws li. Gallium, mercury), nruab nrab-melting (600-1600 ° C, tooj liab, aluminium) thiab refractory (>1600 ° C, tungsten, molybdenum).
Nyob hauv lub ntiaj teb niaj hnub no, cov hlau ntshiab tsis tshua siv vim qhov tseeb tias lawv muaj cov khoom siv lub cev tsawg. Kev lag luam tau ntev thiab siv ntau yam kev sib txuas ntawm cov hlau - alloys, ntau yam thiab cov yam ntxwv ntawm cov khoom loj dua. Lub melting point ntawm cov hlau uas ua rau ntau yam alloys kuj yuav txawv ntawm lub melting point ntawm lawv alloy. Qhov sib txawv ntawm cov tshuaj txiav txim siab qhov kev txiav txim ntawm lawv cov melting lossis crystallization. Tab sis muaj qhov sib npaug ntawm qhov sib npaug ntawm cov hlau uas ua rau cov hlau ua kom khov lossis yaj ib txhij, uas yog, lawv coj zoo li cov khoom sib xws. Cov alloys no hu ua eutectic.
Kev paub txog qhov kub thiab txias yog qhov tseem ceeb heev thaum ua haujlwm nrog hlau, tus nqi no yog qhov tsim nyog ob qho tib si hauv kev tsim khoom, rau kev suav cov tsis muaj alloys, thiab hauv kev ua haujlwm ntawm cov khoom hlau, thaum lub sijhawm hloov pauv kub ntawm cov khoom siv los ntawm cov khoom siv. cov khoom tsim los txiav txim siab qhov kev txwv hauv nws txoj kev siv. Rau kev yooj yim, cov ntaub ntawv nosummarized nyob rau hauv ib lub rooj. Lub rooj melting ntawm cov hlau yog cov ntsiab lus ntawm kev tshawb fawb lub cev ntawm cov yam ntxwv ntawm ntau yam hlau. Kuj tseem muaj cov rooj zoo sib xws rau cov alloys. Lub melting point ntawm hlau kuj tseem ceeb heev nyob ntawm lub siab, yog li ntawd, cov ntaub ntawv nyob rau hauv lub rooj muaj feem xyuam rau ib tug tshwj xeeb siab tus nqi (feem ntau cov no yog ib txwm tej yam kev mob thaum lub siab yog 101.325 kPa). Qhov siab dua, qhov siab dua qhov melting point, thiab vice versa.
