Cov duab nco alloys (SMAs) muaj cov yam ntxwv deformation teb rau thermomechanical stimuli. Thermomechanical stimuli pib los ntawm qhov kub thiab txias, kev hloov pauv, kev hloov pauv ntawm cov khoom-rau-khoom, thiab lwm yam. (qhov kub-txias theem siab yog hu ua austenite, thiab qhov kub-txias theem qis yog hu ua martensite). Kev hloov pauv ntawm lub voj voog rov ua rau qhov kev hloov pauv zuj zus tuaj, yog li cov chaw tsis hloov pauv yuav txo qhov kev ua haujlwm ntawm SMA (hu ua haujlwm qaug zog) thiab tsim cov microcracks, uas thaum kawg yuav ua rau lub cev tsis ua haujlwm thaum tus lej loj txaus. Obviously, nkag siab txog kev qaug zog lub neej tus cwj pwm ntawm cov alloys, daws qhov teeb meem ntawm cov khoom kim heev seem, thiab txo cov khoom tsim thiab cov khoom tsim lub voj voog yuav ua rau muaj kev lag luam loj loj.
Thermo-mechanical qaug zog tsis tau tshawb fawb txog qhov loj, tshwj xeeb tshaj yog qhov tsis muaj kev tshawb fawb txog kev qaug zog tawg propagation nyob rau hauv thermo-mechanical cycles. Hauv kev ua tiav thaum ntxov ntawm SMA hauv biomedicine, lub hom phiaj ntawm kev tshawb fawb qaug zog yog tag nrho lub neej ntawm "tsis muaj qhov tsis xws luag" cov qauv nyob rau hauv cyclic mechanical loads. Hauv cov ntawv thov nrog SMA geometry me me, qaug zog tawg qhov kev loj hlob tsis tshua muaj txiaj ntsig rau lub neej, yog li kev tshawb fawb tsom mus rau kev tiv thaiv kev pib tawg es tsis yog tswj nws txoj kev loj hlob; hauv kev tsav tsheb, kev vibration txo thiab kev siv lub zog nqus, nws yog ib qho tsim nyog kom tau txais lub zog sai. SMA Cheebtsam feem ntau yog qhov loj txaus los tswj cov kev sib tsoo tseem ceeb ua ntej tsis ua haujlwm. Yog li ntawd, kom ua tau raws li qhov tsim nyog kev ntseeg siab thiab kev nyab xeeb, nws yog ib qho tsim nyog yuav tsum nkag siab tag nrho thiab ntsuas qhov kev qaug zog tawg kev loj hlob tus cwj pwm los ntawm kev puas tsuaj rau txoj kev. Daim ntawv thov kev puas tsuaj rau txoj kev cia siab rau lub tswv yim ntawm pob txha mechanics hauv SMA tsis yooj yim. Piv nrog rau cov qauv hlau ib txwm muaj, qhov muaj nyob ntawm qhov hloov pauv hloov pauv thiab cov thermo-mechanical coupling ua rau muaj teeb meem tshiab los piav qhia txog qhov qaug zog thiab overload tawg ntawm SMA.
Cov kws tshawb fawb los ntawm Texas A&M University hauv Tebchaws Meskas tau ua cov tshuab ua kom huv thiab ua rau qaug zog tawg kev loj hlob thwmsim nyob rau hauv Ni50.3Ti29.7Hf20 superalloy thawj zaug, thiab tau npaj ib qho tseem ceeb-raws li Paris-hom kev cai lij choj hais tias yuav siv tau rau haum rau qaug zog. tawg kev loj hlob tus nqi raws li ib tug parameter. Nws yog inferred los ntawm qhov no hais tias txoj kev sib raug zoo nrog tawg tus nqi yuav haum ntawm txawv loading tej yam kev mob thiab geometric configurations, uas yuav siv tau raws li ib tug muaj peev xwm unified descriptor ntawm deformation crack loj hlob nyob rau hauv SMAs. Cov ntaub ntawv cuam tshuam tau luam tawm hauv Acta Materialia nrog lub npe "Ib qho kev piav qhia ntawm kev siv tshuab thiab kev ua haujlwm qaug zog tawg hauv cov duab nco alloys".
Daim ntawv txuas:
https://doi.org/10.1016/j.actamat.2021.117155
Txoj kev tshawb no pom tias thaum Ni50.3Ti29.7Hf20 alloy yog raug rau uniaxial tensile xeem ntawm 180 ℃, lub austenite feem ntau elastically deformed nyob rau hauv tsis tshua muaj kev ntxhov siab nyob rau hauv lub loading txheej txheem, thiab cov tub ntxhais lub modulus yog hais txog 90GPa. Thaum qhov kev ntxhov siab nce mus txog 300MPa Thaum pib ntawm qhov kev hloov pauv zoo, austenite hloov mus rau kev ntxhov siab vim yog martensite; Thaum unloading, kev ntxhov siab vim yog martensite feem ntau dhau los ntawm elastic deformation, nrog ib tug Young's modulus txog 60 GPa, thiab tom qab ntawd hloov mus rau austenite. Los ntawm kev sib koom ua ke, qhov qaug zog tawg qhov kev loj hlob ntawm cov khoom siv tau raug haum rau Paris-hom fais fab txoj cai qhia.
Fig.1 BSE duab ntawm Ni50.3Ti29.7Hf20 kub zoo zoo nco alloy thiab loj tis ntawm oxide hais
Daim duab 2 TEM duab ntawm Ni50.3Ti29.7Hf20 siab kub zoo nco alloy tom qab kev kho cua sov ntawm 550 ℃ × 3h
Daim duab 3 Kev sib raug zoo ntawm J thiab da / dN ntawm cov neeg kho tshuab qaug zog tawg ntawm NiTiHf DCT cov qauv ntawm 180 ℃
Hauv qhov kev sim hauv kab lus no, nws tau ua pov thawj tias cov qauv no tuaj yeem haum rau qhov qaug zog tawg cov ntaub ntawv loj hlob los ntawm txhua qhov kev sim thiab tuaj yeem siv tib cov txheej txheem. Lub hwj chim txoj cai exponent m yog hais txog 2.2. Kev tshawb fawb qaug zog qhia tau hais tias ob qho tib si kev siv tshuab tawg thiab kev tsav tsheb tawg yog kev sib cais ntawm cov pob txha tawg, thiab qhov nquag muaj ntawm hafnium oxide tau ua rau cov kab nrib pleb tawm tsam. Cov txiaj ntsig tau pom tau hais tias ib qho kev cai lij choj hluav taws xob nkaus xwb tuaj yeem ua tiav qhov xav tau zoo sib xws hauv ntau qhov chaw thau khoom thiab cov teeb tsa geometric, yog li muab cov lus piav qhia sib koom ua ke ntawm thermo-mechanical qaug zog ntawm cov duab nco alloys, yog li kwv yees lub zog tsav.
Daim duab 4 SEM duab ntawm qhov tawg ntawm NiTiHf DCT cov qauv tom qab 180 ℃ mechanical fatigue crack growth test
Daim duab 5 Fracture SEM duab ntawm NiTiHf DCT cov qauv tom qab tsav tsheb qaug zog tawg kev loj hlob sim nyob rau hauv qhov kev tsis ncaj ncees tas li ntawm 250 N
Nyob rau hauv cov ntsiab lus, daim ntawv no ua cov neeg kho tshuab ntshiab thiab tsav tsheb qaug zog tawg kev loj hlob thwmsim ntawm npib tsib xee-nplua nuj NiTiHf siab kub zoo nco alloys thawj zaug. Raws li kev sib koom ua ke cyclic, Paris-hom fais fab-txoj cai kev loj hlob kev nthuav qhia yog npaj kom haum rau qhov qaug zog tawg qhov kev loj hlob ntawm txhua qhov kev sim nyob rau hauv ib qho kev txwv.
Post lub sij hawm: Sep-07-2021