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Ib txoj kev tshiab raws li kev xaiv laser melting los tswj cov microstructure ntawm cov khoom hauv cov txheej txheem tsim khoom tau npaj tseg. Lub tshuab no vam khom rau kev tsim cov nthwv dej ultrasonic siab hauv lub pas dej molten los ntawm kev siv laser irradiation uas muaj zog heev. Kev tshawb fawb sim thiab kev sim ua lej qhia tau tias txoj kev tswj hwm no yog qhov ua tau zoo thiab tuaj yeem koom ua ke zoo rau hauv kev tsim cov tshuab laser melting niaj hnub.
Kev tsim khoom ntxiv (AM) ntawm cov khoom sib xyaw ua ke tau loj hlob ntau heev nyob rau xyoo tas los no. Txawm li cas los xij, txawm hais tias muaj ntau yam txheej txheem tsim khoom ntxiv, suav nrog kev xaiv laser yaj (SLM)1,2,3, ncaj qha laser hlau deposition4,5,6, electron beam yaj7,8 thiab lwm yam9,10, Cov Khoom yuav tsis zoo. Qhov no feem ntau yog vim cov yam ntxwv tshwj xeeb ntawm cov txheej txheem molten pas dej khov kho uas cuam tshuam nrog cov thermal gradients siab, cov nqi txias siab, thiab qhov nyuaj ntawm cov cua sov voj voog hauv cov ntaub ntawv yaj thiab rov yaj11, uas ua rau epitaxial noob loj hlob thiab porosity tseem ceeb12,13. Cov txiaj ntsig qhia tau tias, nws yog qhov tsim nyog los tswj cov thermal gradients, cov nqi txias, thiab cov khoom sib xyaw ua ke, lossis siv cov kev poob siab ntxiv los ntawm cov teb sab nraud ntawm ntau yam khoom (piv txwv li, ultrasound) kom ua tiav cov qauv noob zoo sib npaug.
Muaj ntau phau ntawv tshaj tawm txog kev cuam tshuam ntawm kev kho mob vibration rau cov txheej txheem solidification hauv cov txheej txheem casting ib txwm muaj14,15. Txawm li cas los xij, kev siv lub tshav pob sab nraud rau cov khoom yaj tsis tsim cov khoom siv microstructure xav tau. Yog tias qhov ntim ntawm cov kua theem me me, qhov xwm txheej hloov pauv ntau heev. Hauv qhov no, lub tshav pob sab nraud cuam tshuam rau cov txheej txheem solidification. Cov teebmeem electromagnetic tau raug txiav txim siab thaum lub sijhawm muaj zog acoustic16,17,18,19,20,21,22,23,24,25,26,27, arc stirring28 thiab oscillation29, pulsed plasma arcs30,31 thiab lwm txoj kev32. Txuas rau lub substrate siv lub zog ultrasound sab nraud (ntawm 20 kHz). Qhov kev ua kom zoo dua ntawm cov noob qoob loo ultrasound yog vim muaj kev nce ntxiv ntawm thaj chaw compositional subcooling vim yog qhov txo qis ntawm qhov kub thiab kev txhim kho ultrasound los tsim cov crystallites tshiab los ntawm cavitation.
Hauv txoj haujlwm no, peb tau tshawb nrhiav qhov ua tau ntawm kev hloov pauv cov qauv ntawm cov hlau stainless austenitic los ntawm kev siv lub pas dej molten nrog cov suab nthwv dej uas tsim los ntawm lub laser melting nws tus kheej. Kev hloov pauv ntawm qhov teeb meem ntawm lub teeb-nqus nruab nrab ua rau muaj cov nthwv dej ultrasonic, uas hloov pauv qhov microstructure ntawm cov khoom siv. Qhov kev hloov pauv ntawm qhov teeb meem ntawm lub teeb laser no tuaj yeem yooj yim koom ua ke rau hauv cov tshuab luam ntawv SLM 3D uas twb muaj lawm. Cov kev sim hauv txoj haujlwm no tau ua tiav ntawm cov phaj hlau stainless uas cov nto tau raug rau qhov teeb meem laser-modulated. Yog li, technically, kev kho laser nto tau ua tiav. Txawm li cas los xij, yog tias kev kho laser zoo li no tau ua tiav ntawm qhov chaw ntawm txhua txheej, thaum lub sijhawm txheej-los-txheej tsim, cov teebmeem ntawm tag nrho cov ntim lossis ntawm cov khoom xaiv ntawm qhov ntim tau ua tiav. Hauv lwm lo lus, yog tias qhov khoom tau tsim txheej los ntawm txheej, kev kho laser nto ntawm txhua txheej yog sib npaug rau "kev kho laser ntim".
Thaum siv ultrasonic horn-based ultrasonic therapy, lub zog ultrasonic ntawm lub suab sawv ntsug tau faib thoob plaws hauv cov khoom, thaum lub zog ultrasonic uas laser ua rau muaj zog heev nyob ze ntawm qhov chaw uas lub teeb laser raug nqus. Siv lub sonotrode hauv lub tshuab SLM hmoov txaj fusion yog qhov nyuaj vim tias qhov saum npoo ntawm lub txaj hmoov uas raug rau lub teeb laser yuav tsum nyob ruaj khov. Tsis tas li ntawd, tsis muaj kev ntxhov siab ntawm lub tshuab ntawm qhov saum npoo ntawm qhov. Yog li ntawd, kev ntxhov siab acoustic ze rau xoom thiab qhov ceev ntawm cov khoom me me muaj qhov siab tshaj plaws hla tag nrho qhov saum npoo ntawm qhov. Lub suab siab hauv tag nrho lub pas dej molten tsis tuaj yeem tshaj 0.1% ntawm lub siab tshaj plaws uas tsim los ntawm lub taub hau vuam, vim tias qhov ntev ntawm cov nthwv dej ultrasonic nrog zaus ntawm 20 kHz hauv cov hlau tsis xeb yog \(\sim 0.3~\text {m}\), thiab qhov tob feem ntau tsawg dua \(\sim 0.3~\text {mm}\). Yog li ntawd, qhov cuam tshuam ntawm ultrasound ntawm cavitation yuav me me.
Yuav tsum nco ntsoov tias kev siv cov hluav taws xob laser uas muaj zog hloov kho hauv kev tso cov hlau laser ncaj qha yog thaj chaw tshawb fawb nquag35,36,37,38.
Qhov cuam tshuam ntawm cov hluav taws xob laser rau ntawm qhov nruab nrab yog lub hauv paus rau yuav luag txhua txoj kev siv laser 39, 40 rau kev ua cov khoom siv, xws li txiav41, vuam, tawv, khawb42, ntxuav qhov chaw, sib xyaw ua ke ntawm qhov chaw, txhuam qhov chaw43, thiab lwm yam. Kev tsim cov laser tau txhawb nqa kev txhim kho tshiab hauv cov txheej txheem ua cov khoom siv, thiab cov txiaj ntsig pib tau raug sau ua ke hauv ntau qhov kev tshuaj xyuas thiab cov ntawv sau44,45,46.
Yuav tsum nco ntsoov tias txhua yam kev ua tsis ruaj khov ntawm qhov nruab nrab, suav nrog kev ua lasing ntawm qhov nruab nrab uas nqus tau, ua rau muaj kev txhawb nqa ntawm cov nthwv dej acoustic hauv nws nrog ntau dua lossis tsawg dua kev ua haujlwm. Thaum pib, qhov tseem ceeb tshaj plaws yog nyob rau ntawm laser excitation ntawm cov nthwv dej hauv cov kua thiab ntau yam thermal excitation mechanisms ntawm lub suab (thermal expansion, evaporation, volume change thaum lub sijhawm hloov pauv theem, contraction, thiab lwm yam) 47, 48, 49. Ntau monographs50, 51, 52 muab kev tshuaj xyuas theoretical ntawm cov txheej txheem no thiab nws cov kev siv tau.
Cov teeb meem no tau raug tham txog tom qab ntawm ntau lub rooj sib tham, thiab kev siv laser ntawm ultrasound muaj cov ntawv thov hauv ob qho kev siv tshuab laser hauv kev lag luam53 thiab tshuaj54. Yog li ntawd, nws tuaj yeem xav tias lub tswv yim yooj yim ntawm cov txheej txheem uas lub teeb laser pulsed ua rau ntawm qhov nruab nrab nqus tau tsim. Kev tshuaj xyuas laser ultrasonic yog siv rau kev kuaj pom qhov tsis zoo ntawm cov qauv SLM-tsim55,56.
Qhov cuam tshuam ntawm cov nthwv dej laser tsim rau ntawm cov ntaub ntawv yog lub hauv paus ntawm laser shock peening57,58,59, uas kuj siv rau kev kho qhov chaw ntawm cov khoom tsim ntxiv60. Txawm li cas los xij, laser shock strengthening yog qhov zoo tshaj plaws ntawm nanosecond laser pulses thiab cov chaw thauj khoom siv tshuab (piv txwv li, nrog ib txheej kua)59 vim tias kev thauj khoom siv tshuab ua rau lub siab tshaj plaws nce.
Cov kev sim tau ua los tshawb nrhiav cov teebmeem ntawm ntau yam kev ua haujlwm ntawm lub cev rau ntawm cov khoom siv khov kho. Daim duab qhia txog kev ua haujlwm ntawm qhov kev teeb tsa sim tau qhia nyob rau hauv Daim Duab 1. Ib lub laser Nd:YAG solid-state pulsed ua haujlwm hauv hom khiav dawb (lub sijhawm pulse \(\tau _L \sim 150~\upmu \text {s}\ )) tau siv. Txhua lub laser pulse raug xa mus los ntawm ntau cov lim dej neutral density thiab lub phaj beam splitter system. Nyob ntawm kev sib xyaw ua ke ntawm cov lim dej neutral density, lub zog pulse ntawm lub hom phiaj sib txawv ntawm \(E_L \sim 20~\text {mJ}\) mus rau \(E_L \sim 100~\text {mJ}\). Lub laser beam uas cuam tshuam los ntawm lub beam splitter raug pub rau lub photodiode rau kev tau txais cov ntaub ntawv tib lub sijhawm, thiab ob lub calorimeters (photodiodes nrog lub sijhawm teb ntev tshaj \(1~\text {ms}\)) raug siv los txiav txim siab qhov xwm txheej rau thiab cuam tshuam los ntawm lub hom phiaj, thiab ob lub zog ntsuas (photodiodes nrog lub sijhawm teb luv luv \(<10~\text {ns}\)) txhawm rau txiav txim siab qhov xwm txheej thiab lub zog pom kev. Calorimeters thiab cov ntsuas hluav taws xob tau raug calibrated los muab cov nqi hauv cov chav nyob siv lub thermopile detector Gentec-EO XLP12-3S-H2-D0 thiab daim iav dielectric mounted ntawm qhov chaw qauv. Tsom lub beam rau ntawm lub hom phiaj siv lub lens (Antireflection txheej ntawm \(1.06 \upmu \text {m}\), focal ntev \(160~\text {mm}\)) thiab lub beam duav ntawm lub hom phiaj nto 60– \(100~\upmu\text {m}\).
Daim duab qhia txog kev ua haujlwm ntawm qhov kev teeb tsa sim: 1—laser; 2—laser beam; 3—neutral density filter; 4—synchronized photodiode; 5—beam splitter; 6—diaphragm; 7—calorimeter ntawm qhov teeb meem beam; 8 – calorimeter ntawm qhov teeb meem beam; 9 – incident beam power meter; 10 – reflected beam power meter; 11 – focusing lens; 12 – daim iav; 13 – qauv; 14 – broadband piezoelectric transducer; 15 – 2D converter; 16 – positioning microcontroller; 17 – synchronization unit; 18 – multi-channel digital acquisition system nrog ntau yam sampling rates; 19 – personal computer.
Kev kho mob ultrasonic yog ua raws li nram no. Lub laser ua haujlwm hauv hom kev khiav dawb; yog li ntawd lub sijhawm ntawm lub laser pulse yog \(\tau _L \sim 150~\upmu \text {s}\), uas muaj ntau lub sijhawm ntawm kwv yees li \(1.5~\upmu \text {s} \) txhua. Lub sijhawm zoo li ntawm lub laser pulse thiab nws cov spectrum muaj lub hnab ntawv qis-zaus thiab lub siab-zaus modulation, nrog rau qhov nruab nrab zaus ntawm kwv yees li \(0.7~\text {MHz}\), raws li pom hauv Daim Duab 2.- Lub hnab ntawv zaus muab cov cua sov thiab tom qab ntawd yaj thiab evaporation ntawm cov khoom, thaum lub siab zaus Cheebtsam muab cov ultrasonic vibrations vim yog cov nyhuv photoacoustic. Lub waveform ntawm lub ultrasonic pulse tsim los ntawm lub laser yog feem ntau txiav txim siab los ntawm lub sijhawm zoo li ntawm lub laser pulse zog. Nws yog los ntawm \(7~\text {kHz}\) mus rau \ (2~\text {MHz}\), thiab qhov zaus nruab nrab yog \(~ 0.7~\text {MHz}\). Cov suab nrov acoustic vim yog cov teebmeem photoacoustic tau kaw cia siv cov broadband piezoelectric transducers ua los ntawm polyvinylidene fluoride zaj duab xis. Cov waveform kaw tseg thiab nws cov spectrum tau qhia hauv Daim Duab 2. Nws yuav tsum tau sau tseg tias cov duab ntawm cov laser pulses yog ib txwm muaj ntawm lub laser hom khiav dawb.
Kev faib tawm ntawm lub zog laser pulse (a) thiab qhov ceev ntawm lub suab ntawm qhov chaw tom qab ntawm cov qauv (b), spectra ntawm laser pulse (c) thiab ultrasonic pulse (d) nruab nrab tshaj 300 laser pulses (kab liab) rau ib qho laser pulse (kab xiav).
Peb tuaj yeem paub qhov txawv ntawm cov khoom siv qis thiab siab ntawm kev kho mob acoustic uas sib raug rau lub hnab ntawv qis ntawm lub laser pulse thiab lub siab-zaus modulation, raws li. Cov wavelengths ntawm cov nthwv dej acoustic tsim los ntawm lub hnab ntawv laser pulse tshaj \(40~\text {cm}\); yog li ntawd, qhov cuam tshuam tseem ceeb ntawm cov khoom siv broadband siab-zaus ntawm lub teeb liab acoustic ntawm microstructure yog xav tau.
Cov txheej txheem lub cev hauv SLM yog qhov nyuaj thiab tshwm sim tib lub sijhawm ntawm ntau qhov chaw thiab lub sijhawm sib txawv. Yog li ntawd, ntau txoj kev ntsuas yog qhov tsim nyog tshaj plaws rau kev tshuaj xyuas theoretical ntawm SLM. Cov qauv lej yuav tsum xub muaj ntau lub cev. Cov txheej txheem thiab thermophysics ntawm ntau theem nruab nrab "khoom khov-kua yaj" cuam tshuam nrog huab cua inert tuaj yeem piav qhia tau zoo. Cov yam ntxwv ntawm cov khoom siv thermal loads hauv SLM yog raws li hauv qab no.
Cov nqi cua sov thiab txias txog li \(10^6~\text {K}/\text {s}\) /\text{ vim yog kev siv laser irradiation hauv zos nrog lub zog ceev txog li \(10^{13}~\text {W} cm}^2\).
Lub voj voog yaj-khoov kav ntev li ntawm 1 thiab \(10~\text {ms}\), uas ua rau thaj chaw yaj khov sai sai thaum lub sijhawm txias.
Kev ua kom sov sai ntawm qhov chaw kuaj ua rau muaj kev ntxhov siab thermoelastic siab hauv txheej saum npoo. Qhov txaus (txog li 20%) ntawm cov txheej hmoov tau evaporated heev63, uas ua rau muaj kev thauj khoom ntxiv rau ntawm qhov chaw teb rau laser ablation. Yog li ntawd, qhov kev ntxhov siab ua rau muaj kev cuam tshuam loj heev rau qhov geometry ntawm qhov chaw, tshwj xeeb tshaj yog nyob ze cov kev txhawb nqa thiab cov khoom siv nyias nyias. Qhov kub siab hauv pulsed laser annealing ua rau muaj kev tsim cov nthwv dej ultrasonic uas nthuav dav los ntawm qhov chaw mus rau lub substrate. Txhawm rau kom tau txais cov ntaub ntawv kom raug ntawm kev ntxhov siab hauv zos thiab kev faib tawm ntawm kev ntxhov siab, kev sim mesoscopic ntawm qhov teeb meem elastic deformation conjugated rau cua sov thiab pawg hloov pauv tau ua tiav.
Cov qauv tswj hwm ntawm tus qauv suav nrog (1) cov qauv hloov pauv cua sov tsis ruaj khov qhov twg thermal conductivity nyob ntawm theem xeev (hmoov, yaj, polycrystalline) thiab kub, (2) kev hloov pauv hauv elastic deformation tom qab continuum ablation thiab thermoelastic expansion equation. Qhov teeb meem ntawm tus nqi ciam teb yog txiav txim siab los ntawm cov xwm txheej sim. Lub laser flux modulated yog txhais rau ntawm qhov chaw ntawm cov qauv. Convective txias suav nrog conductive heat exchange thiab evaporative flux. Lub mass flux yog txhais raws li kev xam ntawm lub siab vapor saturated ntawm cov khoom evaporating. Kev sib raug zoo ntawm elastoplastic stress-strain yog siv qhov twg thermoelastic stress yog proportional rau qhov sib txawv kub. Rau lub zog nominal \(300~\text {W}\), zaus \(10^5~\text {Hz}\), intermittent coefficient 100 thiab \(200~\upmu \text {m}\) ntawm lub beam txoj kab uas hla.
Daim Duab 3 qhia txog cov txiaj ntsig ntawm kev sim ua lej ntawm thaj chaw molten siv tus qauv lej macroscopic. Lub txoj kab uas hla ntawm thaj chaw fusion yog \(200~\upmu \text {m}\) (\(100~\upmu \text {m}\) radius) thiab \(40~\upmu \text {m}\) tob. Cov txiaj ntsig simulation qhia tau tias qhov kub ntawm qhov chaw hloov pauv hauv zos nrog lub sijhawm raws li \(100~\text {K}\) vim yog qhov sib txawv ntawm qhov sib txawv ntawm lub zog pulse modulation. Cov cua sov \(V_h\) thiab txias \(V_c\) tus nqi yog nyob rau ntawm qhov kev txiav txim ntawm \(10^7\) thiab \(10^6~\text {K}/\text {s}\), feem. Cov nqi no zoo sib xws nrog peb qhov kev tshuaj xyuas yav dhau los64. Qhov kev txiav txim ntawm qhov sib txawv ntawm \(V_h\) thiab \(V_c\) ua rau muaj kev kub ntxhov sai ntawm cov txheej saum npoo, qhov twg thermal conduction mus rau lub substrate tsis txaus los tshem tawm cov cua sov. Yog li ntawd, ntawm \(t=26~\upmu \text {s}\) lub Qhov kub ntawm qhov chaw nce siab txog li \(4800~\text {K}\). Kev ua pa ntawm cov khoom tuaj yeem ua rau qhov chaw ntawm cov qauv raug kev nyuaj siab ntau dhau thiab tev tawm.
Cov txiaj ntsig simulation ntawm thaj chaw yaj ntawm ib lub laser pulse annealing ntawm 316L qauv phaj. Lub sijhawm txij thaum pib ntawm lub pulse mus rau qhov tob ntawm lub pas dej yaj uas ncav cuag qhov siab tshaj plaws yog \(180~\upmu\text {s}\). Lub isotherm\(T = T_L = 1723~\text {K}\) sawv cev rau ciam teb ntawm cov kua thiab cov khoom khov. Cov isobars (kab daj) sib raug rau qhov kev ntxhov siab ntawm cov zis uas suav ua haujlwm ntawm qhov kub thiab txias hauv ntu tom ntej. Yog li ntawd, nyob rau hauv thaj chaw ntawm ob lub isolines (isotherms\(T=T_L\) thiab isobars\(\sigma =\sigma _V(T)\)), cov khoom khov raug rau cov khoom siv kho tshuab muaj zog, uas yuav ua rau muaj kev hloov pauv hauv microstructure.
Cov nyhuv no tau piav qhia ntxiv hauv Daim Duab 4a, qhov twg qib siab hauv thaj chaw molten tau plotted ua haujlwm ntawm lub sijhawm thiab qhov deb ntawm qhov chaw. Ua ntej, tus cwj pwm siab yog cuam tshuam nrog kev hloov kho ntawm lub zog laser pulse piav qhia hauv Daim Duab 2 saum toj no. Lub siab tshaj plaws \text{s}\) ntawm txog \(10~\text {MPa}\) tau pom ntawm txog \(t=26~\upmu). Qhov thib ob, qhov kev hloov pauv ntawm lub siab hauv zos ntawm qhov chaw tswj hwm muaj cov yam ntxwv oscillation zoo ib yam li zaus ntawm \(500~\text {kHz}\). Qhov no txhais tau tias cov nthwv dej siab ultrasonic tau tsim ntawm qhov chaw thiab tom qab ntawd kis mus rau hauv lub substrate.
Cov yam ntxwv xam tau ntawm thaj chaw deformation ze ntawm thaj chaw yaj tau qhia nyob rau hauv daim duab 4b. Laser ablation thiab thermoelastic stress tsim cov elastic deformation waves uas kis mus rau hauv lub substrate. Raws li tuaj yeem pom los ntawm daim duab, muaj ob theem ntawm kev tsim kev ntxhov siab. Thaum lub sijhawm thawj zaug ntawm \(t < 40~\upmu \text {s}\), Mises stress nce mus rau \(8~\text {MPa}\) nrog kev hloov pauv zoo ib yam li qhov siab ntawm qhov chaw. Qhov kev ntxhov siab no tshwm sim vim yog laser ablation, thiab tsis muaj kev ntxhov siab thermoelastic tau pom nyob rau hauv cov ntsiab lus tswj vim tias thaj chaw cuam tshuam los ntawm cua sov thawj zaug me dhau. Thaum cua sov raug dissipated rau hauv lub substrate, qhov chaw tswj tsim kev ntxhov siab thermoelastic siab tshaj \(40~\text {MPa}\).
Cov theem kev ntxhov siab uas tau txais muaj qhov cuam tshuam loj rau qhov sib txuas ntawm cov khoom khov thiab kua thiab tej zaum yuav yog lub tshuab tswj hwm txoj kev khov. Qhov loj ntawm thaj chaw deformation yog 2 txog 3 npaug loj dua li ntawm thaj chaw yaj. Raws li pom hauv Daim Duab 3, qhov chaw ntawm lub isotherm yaj thiab qib kev ntxhov siab sib npaug rau qhov kev ntxhov siab ntawm cov zis tau muab piv. Qhov no txhais tau tias lub pulsed laser irradiation muab cov khoom siv siab hauv cov cheeb tsam hauv zos nrog lub cheeb tsam zoo ntawm 300 thiab \(800~\upmu \text {m}\) nyob ntawm lub sijhawm tam sim ntawd.
Yog li ntawd, qhov kev hloov kho nyuaj ntawm cov pulsed laser annealing ua rau muaj cov nyhuv ultrasonic. Txoj kev xaiv microstructure txawv yog tias piv rau SLM yam tsis muaj ultrasonic loading. Cov cheeb tsam tsis ruaj khov ua rau muaj cov voj voog ntawm kev sib zog thiab ncab hauv cov khoom khov kho. Yog li, kev tsim cov ciam teb tshiab thiab cov ciam teb subgrain ua tau. Yog li ntawd, cov khoom microstructural tuaj yeem hloov pauv tau, raws li qhia hauv qab no. Cov lus xaus tau muab qhov ua tau los tsim cov qauv SLM uas siv pulse modulation. Hauv qhov no, piezoelectric inductor 26 siv rau lwm qhov tuaj yeem raug tshem tawm.
(a) Lub zog siab ua haujlwm ntawm lub sijhawm, xam ntawm qhov deb sib txawv ntawm qhov chaw 0, 20 thiab \(40~\upmu \text {m}\) raws txoj kab sib luag.(b) Lub sijhawm-nyob ntawm Von Mises kev ntxhov siab xam hauv lub matrix khov kho ntawm qhov deb 70, 120 thiab \(170~\upmu \text {m}\) ntawm qhov chaw qauv.
Cov kev sim tau ua rau ntawm AISI 321H stainless hlau phaj nrog qhov ntev \(20\times 20\times 5~\text {mm}\). Tom qab txhua lub laser pulse, lub phaj txav \(50~\upmu \text {m}\), thiab lub laser beam duav ntawm lub hom phiaj nto yog li \(100~\upmu \text {m}\). Txog li tsib lub beam hla tom qab tau ua raws tib txoj kev kom rov yaj ntawm cov khoom ua tiav rau kev ua kom zoo dua. Hauv txhua qhov xwm txheej, thaj chaw rov yaj tau sonicated, nyob ntawm qhov oscillatory ntawm lub laser radiation. Qhov no ua rau muaj kev txo qis ntau dua 5-zaug hauv thaj chaw nruab nrab. Daim duab 5 qhia txog li cas microstructure ntawm thaj chaw laser-yaj hloov pauv nrog tus lej ntawm cov voj voog rov yaj tom qab (dhau).
Cov duab me me (a, d, g, j) thiab (b, e, h, k) - microstructure ntawm laser melted cheeb tsam, cov duab me me (c, f, i, l) - thaj chaw faib ntawm cov noob xim. Shading sawv cev rau cov khoom siv los xam cov histogram. Xim sib raug rau thaj chaw noob (saib cov xim bar saum toj ntawm histogram. Cov duab me me (ac) sib raug rau cov hlau tsis tau kho, thiab cov duab me me (df), (gi), (jl) sib raug rau 1, 3 thiab 5 remelts.
Vim tias lub zog laser pulse tsis hloov ntawm cov kev hla tom qab, qhov tob ntawm thaj chaw molten yog tib yam. Yog li, cov channel tom qab "npog" tag nrho cov dhau los. Txawm li cas los xij, cov histogram qhia tias qhov nruab nrab thiab thaj chaw nruab nrab txo qis nrog rau kev nce ntxiv ntawm cov kev hla. Qhov no yuav qhia tau tias lub laser ua haujlwm rau ntawm lub substrate es tsis yog cov yaj.
Kev ua kom cov noob zoo dua tej zaum yuav yog vim txias sai ntawm lub pas dej ua kua 65. Lwm cov kev sim tau ua tiav uas cov nplaim ntawm cov phaj hlau tsis xeb (321H thiab 316L) raug rau cov hluav taws xob laser txuas ntxiv mus rau hauv huab cua (Daim duab 6) thiab lub tshuab nqus tsev (Daim duab 7). Lub zog laser nruab nrab (300 W thiab 100 W, feem) thiab qhov tob ntawm lub pas dej ua kua yog ze rau cov txiaj ntsig ntawm kev sim ntawm Nd: YAG laser hauv hom kev khiav dawb. Txawm li cas los xij, ib qho qauv columnar ib txwm muaj tau pom.
Cov qauv me me ntawm thaj chaw laser-melted ntawm lub laser nthwv dej tas mus li (300 W lub zog tas mus li, 200 mm/s scan ceev, AISI 321H stainless hlau).
(a) Microstructure thiab (b) electron backscatter diffraction duab ntawm thaj chaw laser-melted hauv lub tshuab nqus tsev nrog lub laser nthwv dej tas mus li (100 W lub zog tas mus li, 200 mm/s scan speed, AISI 316L stainless hlau)\ (\sim 2~\text {mbar}\).
Yog li ntawd, nws tau pom tseeb tias qhov kev hloov kho nyuaj ntawm lub zog laser pulse muaj qhov cuam tshuam loj rau qhov tshwm sim microstructure. Peb ntseeg tias qhov cuam tshuam no yog mechanical hauv xwm thiab tshwm sim vim yog lub cim ntawm ultrasonic vibrations propagating los ntawm qhov chaw irradiated ntawm lub yaj tob rau hauv cov qauv. Cov txiaj ntsig zoo sib xws tau txais hauv 13, 26, 34, 66, 67 siv cov transducers piezoelectric sab nraud thiab sonotrodes muab cov ultrasound siab-intensity hauv ntau yam ntaub ntawv suav nrog Ti-6Al-4V alloy 26 thiab stainless hlau 34 qhov tshwm sim ntawm. Lub mechanism ua tau yog xav tias raws li hauv qab no. Ultrasonic hnyav tuaj yeem ua rau acoustic cavitation, raws li tau pom hauv ultrafast hauv situ synchrotron X-ray imaging. Kev tawg ntawm cov cavitation npuas hauv lem tsim cov nthwv dej poob siab hauv cov khoom siv molten, uas nws lub siab pem hauv ntej ncav cuag txog \ (100 ~ \ text {MPa} \) 69. Cov nthwv dej poob siab no yuav muaj zog txaus los txhawb kev tsim cov nuclei khoom tseem ceeb hauv cov kua dej loj, cuam tshuam cov qauv columnar grain ntawm kev tsim khoom ntxiv txheej-rau-txheej.
Ntawm no, peb xav txog lwm txoj hauv kev uas ua rau muaj kev hloov kho los ntawm kev siv sonication ntau heev. Tom qab khov lawm, cov khoom siv nyob rau qhov kub siab ze rau qhov melting point thiab muaj kev ntxhov siab tsawg heev. Cov nthwv dej ultrasonic ntau heev tuaj yeem ua rau cov yas ntws hloov cov qauv ntawm cov khoom kub, uas khov lawm. Txawm li cas los xij, cov ntaub ntawv sim uas ntseeg tau ntawm qhov kub thiab txias ntawm kev ntxhov siab muaj nyob ntawm \(T\lesssim 1150~\text {K}\) (saib Daim Duab 8). Yog li ntawd, los sim qhov kev xav no, peb tau ua qhov kev sim molecular dynamics (MD) ntawm Fe-Cr-Ni zoo ib yam li AISI 316 L hlau kom ntsuas qhov kev ntxhov siab ntawm cov khoom ze rau qhov melting point. Txhawm rau xam qhov kev ntxhov siab ntawm cov khoom siv, peb tau siv MD shear stress relaxation technique uas tau piav qhia hauv 70, 71, 72, 73. Rau kev suav kev sib cuam tshuam ntawm interatomic, peb tau siv Embedded Atomic Model (EAM) los ntawm 74. Kev sim MD tau ua tiav siv LAMMPS codes 75,76. Cov ntsiab lus ntawm MD simulations yuav raug tshaj tawm rau lwm qhov. Kev xam MD cov txiaj ntsig ntawm kev ntxhov siab ntawm cov qoob loo ua haujlwm ntawm qhov kub thiab txias tau qhia nyob rau hauv daim duab 8 ua ke nrog cov ntaub ntawv sim thiab lwm yam kev ntsuam xyuas 77,78,79,80,81,82.
Kev ntxhov siab rau AISI qib 316 austenitic stainless hlau thiab cov qauv sib xyaw piv rau qhov kub thiab txias rau MD simulations. Kev ntsuas sim los ntawm cov ntaub ntawv siv: (a) 77, (b) 78, (c) 79, (d) 80, (e) 81. saib. (f) 82 yog tus qauv empirical ntawm kev ntxhov siab-kub nyob ntawm kev ntsuas kev ntxhov siab hauv kab thaum lub sijhawm tsim khoom siv laser. Cov txiaj ntsig ntawm kev sim MD loj hauv kev tshawb fawb no tau qhia tias yog \ (\ vartriangleleft \) rau ib qho tsis muaj qhov tsis xws luag tsis kawg thiab \ (\ vartriangleright \) rau cov noob finite coj mus rau hauv tus account qhov nruab nrab ntawm cov noob ntawm Hall-Petch kev sib raug zoo Dimensions \ (d = 50 ~ \ upmu \ text {m} \).
Nws tuaj yeem pom tias ntawm \(T>1500~\text {K}\) qhov kev ntxhov siab poob qis dua \(40~\text {MPa}\). Ntawm qhov tod tes, kev kwv yees kwv yees tias qhov laser-generated ultrasonic amplitude tshaj \(40~\text {MPa}\) (saib daim duab 4b), uas txaus los ua kom cov yas ntws hauv cov khoom kub uas nyuam qhuav khov.
Qhov kev tsim cov qauv me me ntawm 12Cr18Ni10Ti (AISI 321H) austenitic stainless hlau thaum lub sijhawm SLM tau tshawb nrhiav los ntawm kev siv lub zog laser pulsed modulated complex.
Qhov txo qis ntawm cov noob hauv thaj chaw laser yaj tau pom vim yog kev rov yaj laser tas mus li tom qab 1, 3 lossis 5 zaug dhau.
Kev ua qauv macroscopic qhia tau hais tias qhov kwv yees loj ntawm thaj chaw uas ultrasonic deformation yuav cuam tshuam rau qhov solidification pem hauv ntej yog txog li \(1~\text {mm}\).
Tus qauv MD me me qhia tau hais tias lub zog tso zis ntawm AISI 316 austenitic stainless hlau raug txo qis rau \(40~\text {MPa}\) ze ntawm qhov chaw yaj.
Cov txiaj ntsig tau txais qhia txog ib txoj kev los tswj cov microstructure ntawm cov ntaub ntawv siv cov txheej txheem laser modulated nyuaj thiab tuaj yeem ua lub hauv paus rau kev tsim cov kev hloov kho tshiab ntawm cov txheej txheem pulsed SLM.
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