Ua tsaug rau koj tuaj xyuas Nature.com.Qhov browser version koj siv tau txwv kev txhawb nqa rau CSS.Rau qhov kev paub zoo tshaj plaws, peb xav kom koj siv qhov browser tshiab (lossis kaw qhov kev sib raug zoo hauv Internet Explorer).
Lub tshuab tshiab raws li kev xaiv laser melting los tswj cov microstructure ntawm cov khoom nyob rau hauv cov txheej txheem tsim tau thov.Lub tshuab cia siab rau cov tiam ntawm high-siv ultrasonic tsis nyob rau hauv lub molten pas dej ua ke los ntawm complex siv-modulated laser irradiation.Kev tshawb fawb thiab cov zauv simulations qhia tau hais tias qhov kev tswj mechanism yog technically integrated laser thiab yuav ua tau zoo nyob rau hauv cov kev xaiv ntawm laser integrated tshuab.
Additive manufacturing (AM) ntawm complex-puab qhov chaw tau loj hlob nyob rau hauv lub xyoo caum tsis ntev los no.Txawm li cas los xij, txawm hais tias muaj ntau yam kev tsim khoom ntxiv, suav nrog kev xaiv laser melting (SLM) 1,2,3, ncaj qha laser hlau deposition4,5,6, electron beam melting7,8 thiab lwm yam 9,10, Cov khoom yuav raug puas ntsoog.Qhov no feem ntau yog cov txheej txheem ntawm cov yam ntxwv ntawm cov txheej txheem siab poov xab. , thiab qhov nyuaj ntawm cov cua kub mus rau hauv cov ntaub ntawv melting thiab remelting11, uas ua rau epitaxial grain loj hlob thiab tseem ceeb porosity12,13.Cov txiaj ntsig tau pom tias , nws yog ib qho tsim nyog los tswj cov thermal gradients, txias tus nqi, thiab cov alloy muaj pes tsawg leeg, los yog siv lub cev ntxiv shocks los ntawm sab nraud teb ntawm ntau yam khoom (xws li, ultrasound) kom ua tau zoo equiaxed grain lug.
Ntau cov ntawv tshaj tawm muaj kev txhawj xeeb txog cov txiaj ntsig ntawm kev vibration kev kho mob ntawm cov txheej txheem solidification hauv cov txheej txheem casting txheej txheem14,15.Txawm li cas los xij, kev siv sab nraud rau cov khoom tawg tsis tsim cov khoom siv microstructure.Yog tias qhov ntim ntawm cov kua theem me me, qhov xwm txheej hloov pauv ntau heev.Qhov no, sab nraud teb tau cuam tshuam rau cov txheej txheem solidification.18 electromagnetic cuam tshuam, thaum lub sij hawm 19 electromagnetic teb cuam tshuam. 20,21,22,23,24,25,26,27, arc stirring28 thiab oscillation29, pulsed plasma arcs30,31 thiab lwm yam txoj kev32 .Txuas rau lub substrate siv ib tug sab nraud high-siv ultrasound qhov chaw (ntawm 20 kHz).Lub ultrasound-induced plasma arcs30,31 thiab lwm yam txoj kev32 .Txuas mus rau lub substrate siv ib tug sab nraud high-siv ultrasound qhov chaw (ntawm 20 kHz).Lub ultrasound-induced ntawm cov qoob loo ntawm cov gradation ntawm subcorating cov ntsiab lus ntawm qhov kub thiab txias. ment los tsim cov crystallites tshiab los ntawm cavitation.
Hauv kev ua haujlwm no, peb tau tshawb xyuas qhov ua tau ntawm kev hloov pauv cov qauv nplej ntawm austenitic stainless hlau los ntawm sonicating lub pas dej molten nrog lub suab tsis tsim los ntawm lub melting laser nws tus kheej.Qhov kev siv zog ntawm lub teeb hluav taws xob laser ntawm lub teeb-absorbing nruab nrab tshwm sim nyob rau hauv lub cim ntawm ultrasonic tsis, uas hloov lub microstructure ntawm cov ntaub ntawv LM rau hauv cov khoom siv tam sim no. .Cov kev sim hauv txoj haujlwm no tau ua tiav ntawm cov hlau tsis muaj steel hlau uas cov npoo tau raug siv los ntawm kev siv hluav taws xob-modulated laser radiation.So, technically, laser deg kho yog tiav.Txawm li cas los xij, yog tias qhov kev kho laser no tau ua rau ntawm txhua txheej, thaum txheej txheej txheej txheej tsim, cov teebmeem ntawm tag nrho cov ntim lossis ntawm cov txheej txheem ntawm cov ntim tau ua tiav. er ntim kev kho mob".
Whereas nyob rau hauv ultrasonic horn-raws li kev kho mob ultrasonic, lub zog ultrasonic ntawm lub suab yoj sawv ntsug yog muab faib thoob plaws hauv cov khoom, thaum lub laser-induced ultrasonic siv yog heev concentrated nyob ze ntawm qhov chaw uas lub laser hluav taws xob absorbed.Siv ib tug sonotrode nyob rau hauv ib tug SLM hmoov txaj fusion tshuab yog nyuaj vim hais tias lub saum npoo ntawm hmoov txaj raug rau lub laser hluav taws xob ntxiv, qhov tseem ceeb ntawm qhov chaw yuav tsum nyob twj ywm tsis muaj qhov chaw. tic kev ntxhov siab nyob ze ze rau xoom thiab cov lus tshaj tawm muaj qhov siab tshaj plaws ntawm tag nrho saum npoo ntawm qhov chaw.Lub suab siab hauv tag nrho lub pas dej molten tsis tuaj yeem tshaj 0.1% ntawm qhov siab tshaj plaws uas tsim los ntawm lub taub hau vuam, vim tias lub wavelength ntawm ultrasonic tsis muaj zaus ntawm 20 kHz hauv stainless hlau feem ntau yog \(\sim ~ 0. \text {mm}\).Yog li ntawd, cov nyhuv ntawm ultrasound ntawm cavitation tej zaum yuav me me.
Nws yuav tsum raug sau tseg tias kev siv lub zog-modulated laser hluav taws xob nyob rau hauv ncaj qha laser hlau deposition yog ib qho chaw ua haujlwm ntawm kev tshawb fawb 35,36,37,38.
Lub thermal nyhuv ntawm laser hluav taws xob tshwm sim nyob rau hauv nruab nrab yog lub hauv paus rau yuav luag tag nrho cov txheej txheem laser 39, 40 rau cov khoom siv, xws li cutting41, vuam, hardening, drilling42, nto tu, nto alloying, nto polishing43, thiab lwm yam
Nws yuav tsum tau muab sau tseg tias tej yam uas tsis yog-stationary txiav txim nyob rau hauv nruab nrab, nrog rau lasing kev txiav txim ntawm lub absorbing nruab nrab, ua rau lub excitation ntawm acoustic nthwv dej nyob rau hauv nws nrog ntau dua los yog tsawg efficiency.Thaum pib, lub ntsiab tsom xam yog nyob rau hauv lub laser excitation nthwv dej nyob rau hauv cov kua thiab ntau yam thermal excitation mechanisms ntawm lub suab (thermal expansion, evaporation, ntim hloov 7, monograph 4, thiab lwm yam). 50, 51, 52 muab kev soj ntsuam theoretical ntawm cov txheej txheem no thiab nws cov kev siv tau zoo.
Cov teeb meem no tau tham tom qab ntawm ntau lub rooj sib tham, thiab laser excitation ntawm ultrasound muaj daim ntaub ntawv nyob rau hauv ob qho tib si kev lag luam daim ntawv thov ntawm laser technology53 thiab tshuaj54.Yog li ntawd, nws muaj peev xwm txiav txim siab hais tias lub tswv yim tseem ceeb ntawm cov txheej txheem uas pulsed laser lub teeb ua rau ib tug absorbing nruab nrab tau tsim.Laser ultrasonic tshuaj xyuas yog siv rau defect nrhiav kom tau SLM-tsim qauv.55,
Cov nyhuv ntawm laser-generated shock waves ntawm cov ntaub ntawv yog lub hauv paus ntawm laser shock peening57,58,59, uas kuj yog siv rau saum npoo ntawm additively manufactured parts60.Txawm li cas los xij, laser shock reinforcing yog qhov zoo tshaj plaws ntawm nanosecond laser pulses thiab mechanically loaded nto (xws li, nrog ib txheej ntawm cov kua) 59 vim mechanical loading nce siab.
Cov kev sim tau ua los tshawb xyuas qhov tshwm sim ntawm ntau yam ntawm lub cev ntawm lub microstructure ntawm cov ntaub ntawv solidified.Cov kev ua haujlwm ntawm cov kev sim teeb tsa tau pom nyob rau hauv daim duab 1.A pulsed Nd:YAG solid-state laser kev khiav hauj lwm nyob rau hauv free-running hom (pulse duration \(\tau _L \sim 150~\upmu \text {sul.}) dhau los ntawm kev siv lub tshuab lim.Each) s thiab beam splitter phaj system.Txawm li cas los xij, nyob ntawm kev sib xyaw ntawm cov lim dej nruab nrab, lub zog pulse ntawm lub hom phiaj txawv ntawm \(E_L \sim 20 ~ \text {mJ}\) rau \(E_L \sim 100 ~ \text {mJ}\). des nrog lub sij hawm teb ntev tshaj \(1~\text {ms}\)) yog siv los txiav txim qhov xwm txheej rau thiab cuam tshuam los ntawm lub hom phiaj, thiab ob lub zog ntsuas hluav taws xob (photodiodes nrog lub sij hawm teb luv\(<10~\text {ns}\)) los txiav txim qhov xwm txheej thiab pom lub hwj chim kho qhov muag. Calorimeters thiab lub zog ntsuas hluav taws xob tau ntsuas los muab cov txiaj ntsig Gen-P2-E-2 ntsuas ntsuas thiab ntsuas qhov ntsuas kub. Daim iav dielectric mounted ntawm qhov chaw coj mus kuaj.Tom lub nqaj mus rau lub hom phiaj siv lub lens (Antireflection txheej ntawm \(1.06 \upmu \text {m}\), focal length \(160 ~ \text {mm}\)) thiab lub duav duav ntawm lub hom phiaj nto 60– \(100 ~ \upmu\text {m}\).
Lub luag haujlwm schematic daim duab ntawm kev sim teeb tsa: 1-laser;2- laser nqaj;3-Neutral density filter;4 - synchronized photodiode;5 - beam splitter;6 - diaphragm;7-calorimeter ntawm qhov teeb meem kab teeb;8 - calorimeter ntawm reflected beam;9 - qhov teeb meem kab hluav taws xob ntsuas;10 - reflected beam zog ntsuas;11 - tsom iav tsom iav;12 - iav;13 - qauv;14 - broadband piezoelectric transducer;15 - 2D converter;16 - positioning microcontroller;17 - synchronization chav tsev;18 - multi-channel digital acquisition system nrog ntau tus nqi piv txwv;19 - tus kheej lub computer.
Ultrasonic kev kho mob yog nqa tawm raws li nram no.Lub laser ua nyob rau hauv dawb-khiav hom;Yog li ntawd, lub sij hawm ntawm lub laser mem tes yog \(\tau _L \sim 150~\upmu \text {s}\), uas muaj ntau lub sij hawm ntawm kwv yees li \(1.5 ~ \upmu \text {s } \) txhua.Lub cev nqaij daim tawv ntawm lub laser pulse thiab nws spectrum muaj ib tug tsawg-frequency hnab ntawv thiab ib tug high-frequency ntawm 7 MHz. \), raws li qhia hauv daim duab 2.- Lub hnab ntawv zaus muab cov cua sov thiab tom qab melting thiab evaporation ntawm cov khoom, thaum lub siab zaus tivthaiv muab cov ultrasonic vibrations vim photoacoustic nyhuv.Qhov waveform ntawm ultrasonic pulse generated los ntawm lub laser yog tsuas yog txiav txim los ntawm lub sij hawm zoo ntawm lub laser pulse siv.Nws yog los ntawm \(7 ~ \text {kHz}\) mus rau \ (2 ~ \text {MHz}\), thiab qhov chaw zaus yog \(~ 0.7 ~ \text {MHz}\). Acoustic pulses vim cov nyhuv photoacoustic tau sau tseg siv broadband piezoelectric transducers ua los ntawm polyvinylidene fluoride films.Nws yuav tsum tsis txhob specture yoj 2. laser pulses yog ib yam ntawm ib tug dawb-khiav hom laser.
Kev faib tawm ib ntus ntawm laser mem tes siv (a) thiab ceev ntawm lub suab nyob rau sab nraum qab ntawm cov qauv (b), spectra ntawm laser pulse (c) thiab ultrasonic pulse (d) nruab nrab ntawm 300 laser pulses (liab nkhaus) rau ib leeg laser mem tes (xiav nkhaus).
Peb tuaj yeem paub qhov txawv ntawm qhov tsawg zaus thiab cov khoom siv ntau zaus ntawm kev kho acoustic sib haum rau lub hnab ntawv tsawg zaus ntawm lub laser pulse thiab lub siab zaus hloov kho, raws li.Qhov wavelengths ntawm lub suab acoustic wavelengths generated los ntawm lub hnab ntawv laser pulse ntau tshaj li 4 ~ 0.Yog li ntawd, cov txiaj ntsig tseem ceeb ntawm broadband high-frequency Cheebtsam ntawm cov teeb liab acoustic ntawm microstructure yog xav tau.
Cov txheej txheem ntawm lub cev hauv SLM yog qhov nyuaj thiab tshwm sim ib txhij ntawm qhov sib txawv ntawm qhov sib txawv thiab lub cev ntawm lub cev.Yog li ntawd, cov txheej txheem ntau yam yog qhov tsim nyog tshaj plaws rau kev soj ntsuam theoretical ntawm SLM.Mathematical qauv yuav tsum pib ua ntau lub cev.The mechanics thiab thermophysics ntawm multiphase nruab nrab "khoom-kua yaj" interacting nrog ib tug inertly cov yam ntxwv ntawm SLM.
Cua sov thiab cua txias npaum li cas mus txog \(10^6~\text {K}/\text {s}\) /\text{vim localized laser irradiation nrog lub hwj chim ceev mus txog \(10^{13}~\text {W} cm}^2\).
Lub voj voog melting-solidification kav ntev li ntawm 1 thiab \(10 ~ \text {ms}\), uas ua rau kom muaj zog sai ntawm thaj chaw melting thaum lub caij txias.
Cov cua kub ceev ntawm cov qauv saum npoo ua rau muaj kev kub ntxhov siab nyob rau hauv cov txheej txheej saum npoo. Txaus (txog 20%) ntawm cov hmoov txheej yog evaporated 63, uas ua rau muaj kev cuam tshuam ntxiv rau ntawm qhov chaw nyob rau hauv teb rau laser ablation.Yog li ntawd, qhov induced strain ho distorts lub feem geometry. Lub cim ntawm ultrasonic strain nthwv dej uas propagate los ntawm qhov chaw mus rau lub substrate.Yuav kom tau txais cov ntaub ntawv muaj tseeb nyob rau hauv lub zos kev ntxhov siab thiab strain tis, ib tug mesoscopic simulation ntawm elastic deformation teeb meem conjugated rau tshav kub thiab huab hwm coj hloov yog ua.
Cov kev sib npaug ntawm cov qauv suav nrog (1) qhov sib npaug ntawm qhov hloov pauv tsis ruaj khov uas qhov thermal conductivity nyob ntawm theem xeev (hmoov, yaj, polycrystalline) thiab kub, (2) hloov pauv hauv elastic deformation tom qab txuas ntxiv ablation thiab thermoelastic expansion equation.Qhov teeb meem ntawm tus ciam teb yog txiav txim siab los ntawm kev sim ua. flux.Qhov loj flux yog txhais raws li kev xam ntawm cov saturated vapor siab ntawm cov khoom evaporating.Qhov kev sib raug zoo ntawm elastoplastic stress-strain yog siv qhov twg cov thermoelastic stress yog proportional rau qhov kub thiab txias sib txawv.Rau nominal zog \(300 ~ \text {W}\), zaus \(10^5 ~ \text {t Hz}\), \) ntawm txoj kab uas hla zoo.
Daim duab 3 qhia cov txiaj ntsig ntawm cov lej simulation ntawm thaj tsam molten siv cov qauv lej macroscopic.Qhov txoj kab uas hla ntawm thaj tsam fusion yog \(200 ~ \upmu \text {m}\) (\(100 ~ \upmu \text {m}\) vojvoog) thiab \(40 ~ \upmu \text {m}\) qhov tob ntawm lub sij hawm qhia qhov tob (0. K}\) vim yog qhov sib txawv ntawm qhov ntsuas pulse.Qhov 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 yog nyob rau hauv zoo pom zoo nrog peb yav dhau los tsom xam qhov sib txawv \(V_h) Nyob rau hauv ceev overheating ntawm txheej txheej, qhov thermal conduction mus rau lub substrate yog tsis txaus kom tshem tawm cov cua sov. Yog li ntawd, ntawm \(t=26~\upmu \text {s}\) qhov kub saum npoo peaks siab li \(4800 ~ \text {K}\).Vivorous evaporation ntawm cov khoom yuav ua rau cov qauv saum npoo yuav raug tawm.
Tus lej simulation tau tshwm sim ntawm melting cheeb tsam ntawm ib leeg laser pulse annealing ntawm 316L qauv phaj.Lub sij hawm los ntawm qhov pib ntawm lub mem tes mus rau qhov tob ntawm lub pas dej molten ncav cuag tus nqi siab tshaj plaws yog \(180 ~ \upmu\text {s}\).The isotherm\(T = T_L = 1723 ~ \texts cov kab nruab nrab ntawm cov khoom sib khi) sib raug rau cov txiaj ntsig kev ntxhov siab suav nrog kev ua haujlwm ntawm qhov kub thiab txias hauv ntu tom ntej.Yog li ntawd, nyob rau hauv qhov chaw nruab nrab ntawm ob lub isolines (isotherms\(T = T_L\) thiab isobars\(\sigma = \sigma _V(T)\)), cov theem khoom yog raug rau cov neeg kho tshuab muaj zog loads, uas tej zaum yuav ua rau muaj kev hloov hauv microstructure.
Cov nyhuv no tau piav qhia ntxiv nyob rau hauv daim duab 4a, qhov twg lub siab theem nyob rau hauv lub molten cheeb tsam yog plotted raws li ib tug muaj nuj nqi ntawm lub sij hawm thiab nyob deb ntawm lub nto. Ua ntej, lub siab tus cwj pwm yog txuam nrog lub modulation ntawm lub laser pulse siv tau piav nyob rau hauv daim duab 2 saum toj no.A siab tshaj plaws siab \text{s}\) ntawm txog \(10 ~ \ lub fluctuation ntawm 6) ~ (m. ation ntawm lub zog hauv zos ntawm qhov chaw tswj muaj tib yam oscillation yam ntxwv raws li qhov zaus ntawm \(500 ~ \text {kHz}\).
Cov yam ntxwv ntawm lub deformation cheeb tsam ze ntawm lub melting zone yog qhia nyob rau hauv daim duab 4b.Laser ablation thiab thermoelastic kev nyuaj siab tsim elastic deformation nthwv dej uas propagate mus rau hauv lub substrate.Raws li tau pom los ntawm daim duab, muaj ob theem ntawm kev nyuaj siab tiam.Thaum thawj theem ntawm \(t < 40 ~ \upmu \text {s}\) zoo ib yam li cov ntaub ntawv ntawm lub substrate. 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 qhov pib tshav kub cuam tshuam qhov chaw me me dhau lawm.Thaum tshav kub dissipated rau hauv substrate, qhov taw tes tswj generates siab thermal stress saum toj no \(40 ~ \text {MPa}\).
Qhov tau txais modulated kev ntxhov siab muaj qhov cuam tshuam tseem ceeb ntawm cov khoom-kua interface thiab tej zaum yuav yog cov tswj kev tswj hwm txoj hauv kev solidification.Qhov loj ntawm thaj tsam deformation yog 2 mus rau 3 npaug loj dua li ntawm thaj tsam melting.Raws li pom nyob rau hauv daim duab 3, qhov chaw ntawm lub melting isotherm thiab cov kev ntxhov siab theem sib npaug zos rau cov yield kev nyuaj siab yog muab piv nrog cov neeg kho tshuab txoj kab uas hla. 300 thiab \(800~\upmu \text {m}\) nyob ntawm lub sij hawm instantaneous.
Yog li ntawd, lub complex modulation ntawm lub pulsed laser annealing ua rau cov nyhuv ultrasonic.Qhov kev xaiv microstructure yog txawv yog tias piv rau SLM yam tsis muaj ultrasonic loading.Deformed tsis ruaj tsis khov cheeb tsam ua rau lub sij hawm mus rau lub sij hawm ntawm compression thiab stretching nyob rau hauv cov khoom theem. Yog li, lub tsim ntawm tshiab grain ciam teb thiab subgrain ciam teb yuav ua tau raws li qhov kev xav tau ntawm microstructure. Muaj peev xwm tsim tau ib qho kev hloov pauv ntawm cov mem tes-vim ultrasound-tsav SLM qauv. Hauv qhov no, piezoelectric inductor 26 siv lwm qhov tuaj yeem raug cais tawm.
(a) Siab raws li lub sijhawm ua haujlwm, suav ntawm qhov sib txawv ntawm qhov chaw 0, 20 thiab \(40 ~ \upmu \text {m}\) raws li axis ntawm symmetry.(b) Lub sij hawm-dependent Von Mises kev ntxhov siab suav hauv cov khoom matrix ntawm qhov deb 70, 120 thiab \(170 ~ \upm) ntawm tus qauv \
Kev sim tau ua nyob rau ntawm AISI 321H stainless hlau daim hlau nrog qhov ntev \(20\times 20\times 5~\text {mm}\).Tom qab txhua lub laser mem tes, lub phaj txav \(50 ~\upmu \text {m}\), thiab lub laser beam duav ntawm lub hom phiaj nto yog hais txog \(100 ~ \upmu). remelting ntawm cov khoom ua tiav rau grain refinement.Txhua qhov xwm txheej, thaj tsam remelted yog sonicated, nyob ntawm oscillatory tivthaiv ntawm lub laser hluav taws xob.Qhov no ua rau ib tug ntau tshaj li 5-fold txo nyob rau hauv nruab nrab grain cheeb tsam.Daim duab 5 qhia tau hais tias yuav ua li cas lub microstructure ntawm lub laser-melted cheeb tsam hloov nrog tus naj npawb ntawm remelting cycles tom ntej (passes).
Subplots (a, d, g, j) thiab (b, e, h, k) - microstructure ntawm laser melted cheeb tsam, subplots (c, f, i, l) - thaj tsam faib ntawm cov xim xim.Shading sawv cev rau cov khoom siv los suav cov histogram.Colors sib haum rau thaj tsam lis (saib cov xim bar nyob rau sab saum toj ntawm histogram. Subplots (ac) sib raug rau cov hlau tsis zoo, thiab subplots (df), (gi), (jl) sib haum rau 1, 3 thiab 5 remelts.
Txij li thaum lub zog laser pulse tsis hloov ntawm qhov txuas ntxiv tom ntej, qhov tob ntawm thaj tsam molten yog tib yam.Yog li, cov channel txuas ntxiv tom qab tag nrho "npog" yav dhau los.Txawm li cas los xij, cov histogram qhia tau hais tias qhov nruab nrab thiab nruab nrab grain cheeb tsam txo nrog nce tus naj npawb ntawm passes.Qhov no yuav qhia tau hais tias lub laser yog ua nyob rau hauv lub substrate es lub yaj.
Grain refinement tej zaum yuav tshwm sim los ntawm ceev ceev ntawm lub molten pas dej ua ke 65.Lwm txheej ntawm thwmsim tau ua nyob rau hauv uas cov nto ntawm stainless hlau daim hlau (321H thiab 316L) tau raug mus tas li yoj laser hluav taws xob nyob rau hauv cov huab cua (Fig. 6) thiab nqus tsev vacuum (Fig. 7).Qhov nruab nrab laser hwj chim (300 W thiab 316L) yog fwm qhov kev sim ntawm poov xab thiab 10. :YAG laser nyob rau hauv dawb-khiav hom.Txawm li cas los xij, ib qho qauv columnar raug pom.
Microstructure ntawm lub laser-melted cheeb tsam ntawm ib tug nruam yoj laser (300 W tas li lub zog, 200 mm / s scan ceev, AISI 321H stainless hlau).
(a) Microstructure thiab (b) electron backscatter diffraction dluab ntawm cheeb tsam laser-melted nyob rau hauv lub tshuab nqus tsev nrog ib tug nruam yoj laser (100 W tas li lub zog, 200 mm / s scan ceev, AISI 316L stainless hlau)\ (\sim 2 ~ \ text {mbar}\).
Yog li ntawd, nws tau pom meej meej tias qhov kev hloov kho ntawm lub laser pulse siv tau muaj txiaj ntsig zoo rau qhov tshwm sim microstructure.Peb ntseeg tias cov nyhuv no yog cov neeg kho tshuab hauv qhov xwm txheej thiab tshwm sim vim yog lub cim ntawm ultrasonic vibrations propagating los ntawm irradiated nto ntawm cov yaj sib sib zog nqus mus rau hauv cov qauv.Similar tau txais nyob rau hauv 13, 26, 36, 36, 6, 6, 26, 26, 36, 6, 26, 36, 6, 26, 26, 36, 6. Ultrasound nyob rau hauv ntau yam ntaub ntawv xws li Ti-6Al-4V alloy 26 thiab stainless hlau 34 qhov tshwm sim ntawm.Qhov ua tau mechanism yog speculated raws li nram no.Intense ultrasound yuav ua rau acoustic cavitation, raws li pom nyob rau hauv ultrafast nyob rau hauv situ synchrotron X-ray imaging.Lub cev qhuav dej ntawm lub cavitation npuas nyob rau hauv lem generates shock waves nyob rau hauv lub siab moltenucha yoj 6 (cov ntaub ntawv ntawm lub siab moltenuch) ~ 6. s tej zaum yuav muaj zog txaus los txhawb qhov tsim ntawm qhov tseem ceeb ntawm cov khoom tseem ceeb-theem nuclei hauv cov kua dej ntau, cuam tshuam cov qauv kab lis kev cai ntawm txheej txheej-los ntawm-txheej additive manufacturing.
Ntawm no, peb tawm tswv yim lwm lub luag haujlwm rau kev hloov kho cov qauv los ntawm kev mob siab sonication.Tam sim tom qab solidification, cov khoom yog nyob rau ntawm qhov kub thiab txias ze rau lub melting point thiab muaj ib tug tsis tshua muaj yield stress.Intense ultrasonic tsis yuav ua rau cov yas ntws los hloov cov grain qauv ntawm kub, tsuas yog solidified cov ntaub ntawv.Txawm li cas los xij, cov ntaub ntawv sim kev sim ntawm qhov ntsuas kub 1 \ K 5 tsis muaj kev vam khom. ) (saib daim duab 8).Yog li ntawd, txhawm rau ntsuas qhov kev xav no, peb tau ua qhov kev sim molecular dynamics (MD) simulations ntawm Fe-Cr-Ni muaj pes tsawg leeg zoo ib yam li AISI 316 L steel txhawm rau ntsuas cov txiaj ntsig kev ntxhov siab nyob ze ntawm qhov melting point.Rau xam cov txiaj ntsig kev ntxhov siab, peb siv MD shear 7 7 kev sib cuam tshuam kev ntxhov siab 7 2. , peb siv Embedded Atomic Model (EAM) los ntawm 74.MD simulations tau ua tiav siv LAMMPS cov lej 75,76.Cov ntsiab lus ntawm MD simulations yuav raug luam tawm rau lwm qhov.The MD suav cov txiaj ntsig ntawm kev ntxhov siab los ntawm kev ua haujlwm ntawm qhov kub thiab txias yog qhia hauv daim duab 8 nrog rau cov ntaub ntawv muaj kev sim thiab lwm yam 78,8,79.
Kev ntxhov siab rau AISI qib 316 austenitic stainless hlau thiab cov qauv muaj pes tsawg leeg piv rau qhov kub thiab txias rau MD simulations.Kev ntsuas kev ntsuas los ntawm cov ntaub ntawv: (a) 77, (b) 78, (c) 79, (d) 80, (e) 81.Refer to.(f)82 yog ib qho kev ntsuas kev ntxhov siab ntxiv rau lub sij hawm laser-txoj kev ywj pheej itive manufacturing.Cov txiaj ntsig ntawm qhov loj-scale MD simulations nyob rau hauv txoj kev tshawb no yog denoted li \(\vartriangleft\) rau ib tug defect-dawb infinite ib crystal thiab \(\vartriangleright\) rau finite grains noj mus rau hauv tus account qhov nruab nrab grain loj ntawm Hall-Petch relation Dimensions\(d = 50 ~ \upmu). \text {m.
Nws tuaj yeem pom tau tias ntawm \(T> 1500 ~ \text {K}\) cov txiaj ntsig kev ntxhov siab poob qis hauv qab \(40 ~ \text {MPa}\). Ntawm qhov tod tes, kev kwv yees kwv yees tias lub laser-tsim ultrasonic amplitude tshaj \(40 ~ \text {MPa}\) (saib daim duab 4b), uas yog txaus rau induce cov khoom yas txaus.
Lub microstructure tsim ntawm 12Cr18Ni10Ti (AISI 321H) austenitic stainless hlau thaum lub sij hawm SLM tau sim sim siv lub complex siv-modulated pulsed laser qhov chaw.
Cov qoob loo loj txo nyob rau hauv cheeb tsam laser melting tau pom vim qhov txuas ntxiv laser remelting tom qab 1, 3 lossis 5 dhau.
macroscopic qauv qhia tau hais tias qhov kwv yees qhov loj ntawm thaj av uas ultrasonic deformation yuav zoo cuam tshuam rau lub hauv ntej solidification yog mus txog \(1~\text {mm}\).
Tus qauv microscopic MD qhia tau hais tias lub zog tawm los ntawm AISI 316 austenitic stainless hlau tau txo qis rau \(40 ~ \text {MPa}\) nyob ze ntawm lub melting point.
Cov txiaj ntsig tau los qhia txog ib txoj hauv kev los tswj cov microstructure ntawm cov ntaub ntawv siv cov txheej txheem hloov kho laser thiab tuaj yeem ua lub hauv paus rau kev tsim cov kev hloov kho tshiab ntawm cov txheej txheem SLM.
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