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Njira yatsopano yochokera pa kusungunuka kwa laser yosankhidwa kuti ilamulire kapangidwe ka zinthu zomwe zikugwiritsidwa ntchito popanga ikuperekedwa. Njirayi imadalira kupanga mafunde amphamvu kwambiri mu dziwe losungunuka pogwiritsa ntchito kuwala kwa laser kosinthasintha. Kafukufuku woyesera ndi ma simulation a manambala akuwonetsa kuti njira yowongolera iyi ndi yotheka ndipo ikhoza kuphatikizidwa bwino mu kapangidwe ka makina osungunula a laser osankhidwa amakono.
Kupanga zowonjezera (AM) za zigawo zooneka ngati zovuta kwakula kwambiri m'zaka zaposachedwa. Komabe, ngakhale njira zosiyanasiyana zopangira zowonjezera, kuphatikizapo kusungunuka kwa laser (SLM)1,2,3, kuyika zitsulo mwachindunji za laser4,5,6, kusungunuka kwa electron beam7,8 ndi zina9,10, Zigawozo zitha kukhala ndi vuto. Izi makamaka chifukwa cha makhalidwe enieni a njira yolimba ya dziwe losungunuka yogwirizana ndi kutentha kwambiri, kuzizira kwambiri, komanso zovuta za kutentha pazinthu zosungunulira ndi kusungunulira11, zomwe zimapangitsa kukula kwa tirigu wa epitaxial ndi porosity yayikulu12,13. Zotsatira zake zikuwonetsa kuti, ndikofunikira kuwongolera kutentha, kuzizira, ndi kapangidwe ka alloy, kapena kugwiritsa ntchito ma shock ena akuthupi kudzera m'minda yakunja ya zinthu zosiyanasiyana (monga ultrasound) kuti mupeze kapangidwe ka tirigu kofanana.
Mabuku ambiri akukhudzidwa ndi momwe kugwedezeka kwa madzi kumakhudzira njira yolimba mu njira zachikhalidwe zopangira 14,15. Komabe, kugwiritsa ntchito munda wakunja ku kusungunuka kwa bulk sikupanga kapangidwe kake ka zinthu komwe kakufunika. Ngati kuchuluka kwa gawo lamadzimadzi kuli kochepa, zinthu zimasintha kwambiri. Pankhaniyi, munda wakunja umakhudza kwambiri njira yolimba. Zotsatira za maginito zaganiziridwa panthawi ya minda yamphamvu ya acoustic16,17,18,19,20,21,22,23,24,25,26,27, arc stirging28 ndi oscillation29, pulsed plasma arcs30,31 ndi njira zina32. Lumikizani ku substrate pogwiritsa ntchito gwero lakunja la ultrasound lamphamvu kwambiri (pa 20 kHz). Kukonzanso kwa tirigu komwe kumachitika chifukwa cha ultrasound kumachitika chifukwa cha kuchuluka kwa compositional subcooling zone chifukwa cha kuchepa kwa kutentha komanso kuwonjezeka kwa ultrasound kuti apange makristali atsopano kudzera mu cavitation.
Mu ntchitoyi, tafufuza kuthekera kosintha kapangidwe ka tinthu tating'onoting'ono ta austenitic stainless steels poika mafunde a phokoso pa dziwe losungunuka ndi mafunde a phokoso opangidwa ndi laser yosungunuka yokha. Kusintha kwa mphamvu ya laser radiation pa malo olandirira kuwala kumabweretsa kupanga mafunde a ultrasound, omwe amasintha kapangidwe ka zinthuzo. Kusintha kwa mphamvu kwa laser radiation kumatha kuphatikizidwa mosavuta mu ma printers a SLM 3D omwe alipo. Kuyesera mu ntchitoyi kunachitika pa mbale zachitsulo zosapanga dzimbiri zomwe pamwamba pake pankawonekera kuwala kwa laser komwe kumasinthidwa. Chifukwa chake, mwaukadaulo, chithandizo cha pamwamba pa laser chimachitidwa. Komabe, ngati chithandizo cha laser choterechi chikuchitika pamwamba pa gawo lililonse, panthawi yomanga gawo ndi gawo, zotsatira zake pa voliyumu yonse kapena pazigawo zosankhidwa za voliyumu zimakwaniritsidwa. Mwanjira ina, ngati gawolo lapangidwa ndi gawo ndi gawo, chithandizo cha pamwamba pa laser cha gawo lililonse ndi chofanana ndi "chithandizo cha voliyumu ya laser".
Pamene mu chithandizo cha ultrasound chogwiritsa ntchito nyanga ya ultrasonic, mphamvu ya ultrasound ya mafunde oyima imagawidwa mu gawo lonselo, pomwe mphamvu ya ultrasound yoyambitsidwa ndi laser imakhala yolimba kwambiri pafupi ndi pomwe kuwala kwa laser kumayamwa. Kugwiritsa ntchito sonotrode mu makina olumikizira ufa a SLM powder bed ndizovuta chifukwa pamwamba pa bedi la ufa lomwe limawonetsedwa ku kuwala kwa laser liyenera kukhala losasunthika. Kuphatikiza apo, palibe kupsinjika kwamakina pamwamba pa gawolo. Chifukwa chake, kupsinjika kwa mawu kuli pafupi ndi zero ndipo liwiro la tinthu limakhala ndi ma amplitude apamwamba pamwamba pa gawo lonselo. Kupanikizika kwa mawu mkati mwa dziwe lonse losungunuka sikungapitirire 0.1% ya kupsinjika kwakukulu komwe kumapangidwa ndi mutu wowotcherera, chifukwa kutalika kwa mafunde a ultrasound okhala ndi pafupipafupi ya 20 kHz mu chitsulo chosapanga dzimbiri ndi \(\sim 0.3~\text {m}\), ndipo kuya kwake nthawi zambiri kumakhala kochepera \(\sim 0.3~\text {mm}\). Chifukwa chake, zotsatira za ultrasound pa cavitation zitha kukhala zochepa.
Tiyenera kudziwa kuti kugwiritsa ntchito mphamvu ya laser yosinthidwa mphamvu mu laser metal deposition mwachindunji ndi gawo lofufuza lomwe likufunika kwambiri35,36,37,38.
Mphamvu ya kutentha kwa kuwala kwa laser pa chinthucho ndiye maziko a njira zonse za laser 39, 40 zokonzera zinthu, monga kudula 41, kuwotcherera, kuuma, kuboola 42, kuyeretsa pamwamba, kuphatikiza pamwamba, kupukuta pamwamba 43, ndi zina zotero. Kupangidwa kwa laser kunayambitsa chitukuko chatsopano mu njira zokonzera zinthu, ndipo zotsatira zoyambirira zafotokozedwa mwachidule mu ndemanga zambiri ndi ma monograph 44, 45, 46.
Tiyenera kudziwa kuti chilichonse chomwe sichinayime pa sing'anga, kuphatikizapo kuchitapo kanthu pang'onopang'ono pa sing'anga yoyamwa, chimabweretsa kusonkhezera kwa mafunde a acoustic mkati mwake ndi mphamvu zochepa. Poyamba, cholinga chachikulu chinali kusonkhezera kwa mafunde pogwiritsa ntchito laser mu zakumwa ndi njira zosiyanasiyana zosonkhezera kutentha kwa mawu (kukulitsa kutentha, kuphulika kwa mpweya, kusintha kwa voliyumu panthawi yosintha kwa gawo, kufupika, ndi zina zotero) 47, 48, 49. Ma monograph ambiri 50, 51, 52 amapereka kusanthula kwamalingaliro kwa njirayi ndi momwe ingagwiritsidwire ntchito.
Nkhani zimenezi zinakambidwa pambuyo pake pamisonkhano yosiyanasiyana, ndipo kusonkhezera kwa ultrasound pogwiritsa ntchito laser kumagwiritsidwa ntchito m'mafakitale onse a ukadaulo wa laser53 komanso zamankhwala54. Chifukwa chake, tinganene kuti lingaliro loyambira la njira yomwe kuwala kwa laser komwe kumayendetsedwa kumagwirira ntchito pa chinthu choyamwa chakhazikitsidwa. Kuyang'anira kwa ultrasound pogwiritsa ntchito laser kumagwiritsidwa ntchito pozindikira zolakwika za zitsanzo zopangidwa ndi SLM55,56.
Zotsatira za mafunde opangidwa ndi laser pa zinthu ndiye maziko a laser shock peening57,58,59, yomwe imagwiritsidwanso ntchito pochiza pamwamba pa ziwalo zopangidwa ndi zowonjezera60. Komabe, kulimbitsa laser shock ndikothandiza kwambiri pa nanosecond laser pulses ndi malo odzazidwa ndi makina (monga, ndi wosanjikiza wamadzimadzi)59 chifukwa makina odzaza amawonjezera kuthamanga kwamphamvu.
Kuyesera kunachitika kuti afufuze zotsatira zomwe zingachitike chifukwa cha minda yosiyanasiyana ya thupi pa kapangidwe ka zinthu zolimba. Chithunzi chogwira ntchito cha kukhazikitsa koyeserera chikuwonetsedwa mu Chithunzi 1. Laser yolimba ya Nd:YAG yomwe imagwira ntchito momasuka (nthawi ya pulse \(\tau _L \sim 150~\upmu \text {s}\ )) idagwiritsidwa ntchito. Kugunda kulikonse kwa laser kumadutsa mu mndandanda wa zosefera za neutral density ndi dongosolo la beam splitter plate. Kutengera ndi kuphatikiza kwa zosefera za neutral density, mphamvu ya pulse pa chandamale imasiyana kuyambira \(E_L \sim 20~\text {mJ}\) mpaka \(E_L \sim 100~\text {mJ}\) . Mtambo wa laser womwe umawonetsedwa kuchokera ku beam splitter umaperekedwa ku photodiode kuti upeze deta nthawi imodzi, ndipo ma calorimeter awiri (ma photodiode omwe nthawi yayitali yoyankha imapitirira \(1~\text {ms}\)) amagwiritsidwa ntchito kudziwa zomwe zachitika ndi zomwe zawonetsedwa kuchokera ku chandamale, ndi ma power meters awiri (ma photodiode omwe ali ndi yankho lalifupi). nthawi\(<10~\text {ns}\)) kuti mudziwe zomwe zachitika komanso mphamvu yowunikira. Ma caloriemeter ndi ma power meter adayesedwa kuti apereke ma values ​​​​mu ma actual units pogwiritsa ntchito thermopile detector Gentec-EO XLP12-3S-H2-D0 ndi galasi la dielectric lomwe lili pamalo oyeserera. Yang'anani mtandawo pa chandamale pogwiritsa ntchito lenzi (Antireflection coating pa \(1.06 \upmu \text {m}\), focal length \(160~\text {mm}\)) ndi beam waist pamwamba pa chandamale 60– \(100~\upmu\text {m}\).
Chithunzi chogwira ntchito cha kapangidwe kake ka kuyesera: 1—laser; 2—laser beam; 3—neutral density filter; 4—photodiode yolumikizidwa; 5—beam splitter; 6—diaphragm; 7—calorimeter ya incident beam; 8—calorimeter ya reflective beam; 9—incident beam power meter; 10—reflective beam power meter; 11—focusing lens; 12—glass; 13—sample; 14—broadband piezoelectric transducer; 15—2D converter; 16—positioning microcontroller; 17—synchronization unit; 18—multi-channel digital acquisition system with various sampling rates; 19—personal computer.
Chithandizo cha ultrasound chimachitika motere. Laser imagwira ntchito momasuka; chifukwa chake nthawi ya pulse ya laser ndi \(\tau _L \sim 150~\upmu \text {s}\), yomwe imakhala ndi nthawi zingapo pafupifupi \(1.5~\upmu \text {s} \) iliyonse. Kapangidwe kake ka pulse ya laser ndi sipekitiramu yake imakhala ndi envelopu yotsika komanso modulation ya ma frequency apamwamba, yokhala ndi ma frequency apakati pafupifupi \(0.7~\text {MHz}\), monga momwe zasonyezedwera pa Chithunzi 2.- Envelopu yofupikitsa imapereka kutentha ndi kusungunuka ndi kutuluka kwa zinthuzo pambuyo pake, pomwe gawo la ma frequency apamwamba limapereka kugwedezeka kwa ultrasound chifukwa cha mphamvu ya photoacoustic. Mafunde a pulse ya ultrasonic yopangidwa ndi laser amatsimikiziridwa makamaka ndi mawonekedwe a nthawi ya mphamvu ya pulse ya laser. Ndi kuyambira pa \(7~\text {kHz}\) mpaka \ (2~\text {MHz}\), ndipo ma frequency apakati ndi \(~ 0.7~\text {MHz}\). Ma pulse a acoustic chifukwa cha photoacoustic effect adajambulidwa pogwiritsa ntchito ma transducer a broadband piezoelectric opangidwa ndi mafilimu a polyvinylidene fluoride. Ma waveform ojambulidwa ndi ma spectrum ake akuwonetsedwa mu Chithunzi 2. Tiyenera kudziwa kuti mawonekedwe a ma pulse a laser ndi ofanana ndi a laser yothamanga.
Kugawa kwakanthawi kwa mphamvu ya kugunda kwa laser (a) ndi liwiro la phokoso kumbuyo kwa chitsanzo (b), ma spectra a kugunda kwa laser (c) ndi kugunda kwa ultrasonic (d) kunali pafupifupi ma pulse opitilira 300 a laser (curve yofiira) pa pulse imodzi ya laser (curve yabuluu).
Tikhoza kusiyanitsa bwino zigawo za ma frequency otsika ndi ma frequency apamwamba za chithandizo cha acoustic zomwe zimagwirizana ndi ma frequency otsika a laser pulse ndi ma high-frequency modulation, motsatana. Mafunde a ma acoustic wave opangidwa ndi laser pulse envelope amaposa \(40~\text {cm}\); chifukwa chake, zotsatira zazikulu za zigawo za broadband high-frequency za chizindikiro cha acoustic pa microstructure zikuyembekezeka.
Machitidwe a thupi mu SLM ndi ovuta ndipo amapezeka nthawi imodzi pamlingo wosiyana wa malo ndi nthawi. Chifukwa chake, njira zambiri ndizoyenera kwambiri pakusanthula kwa chiphunzitso cha SLM. Zitsanzo za masamu ziyenera kukhala zambiri poyamba. Kapangidwe ndi thermophysics ya medium ya magawo ambiri "solid-liquid melt" yolumikizana ndi mpweya wopanda mpweya imatha kufotokozedwa bwino. Makhalidwe a katundu wa kutentha kwa zinthu mu SLM ndi awa:
Kutentha ndi kuzizira kumafika pa \(10^6~\text {K}/\text {s}\) /\text{ chifukwa cha kuwala kwa laser komwe kumakhala ndi mphamvu zambiri mpaka \(10^{13}~\text {W} cm}^2\).
Kusungunuka ndi kulimba kwa madzi kumatenga pakati pa 1 ndi \(10~\text {ms}\), zomwe zimathandiza kuti malo osungunuka azilimba mofulumira panthawi yozizira.
Kutentha mofulumira kwa pamwamba pa chitsanzo kumapangitsa kuti pakhale kupsinjika kwakukulu kwa thermoelastic pamwamba. Gawo lokwanira (mpaka 20%) la ufa limasungunuka mwamphamvu, zomwe zimapangitsa kuti pakhale kupanikizika kowonjezereka pamwamba poyankha kuchotsedwa kwa laser. Chifukwa chake, kupsinjika komwe kumachitika kumasokoneza kwambiri mawonekedwe a gawo, makamaka pafupi ndi zothandizira ndi zinthu zoonda. Kuthamanga kwakukulu kwa kutentha mu pulsed laser annealing kumapangitsa kuti pakhale mafunde a ultrasonic strain omwe amafalikira kuchokera pamwamba kupita ku substrate. Kuti mupeze deta yolondola yokhudza kupsinjika kwapafupi ndi kugawa kwa kupsinjika, kuyerekezera kwa mesoscopic kwa vuto la elastic deformation lomwe limalumikizidwa ndi kutentha ndi kusamutsa kwa misa kumachitika.
Ma equation olamulira a chitsanzochi akuphatikizapo (1) ma equation osakhazikika a kutentha komwe kutentha kumadalira momwe kutentha kumayendera (ufa, kusungunuka, polycrystalline) ndi kutentha, (2) kusinthasintha kwa elastic deformation pambuyo pa continuum ablation ndi thermoelastic expansion equation. Vuto la malire limatsimikiziridwa ndi mikhalidwe yoyesera. Modulated laser flux imafotokozedwa pamwamba pa chitsanzo. Convective cooling imaphatikizapo conductive heat exchange ndi evaporative flux. Mass flux imafotokozedwa kutengera kuwerengera kwa saturated vaporization pressure ya evaporating material. Elastoplastic stress-strain relationship imagwiritsidwa ntchito pomwe thermoelastic stress imagwirizana ndi kusiyana kwa kutentha. Pa mphamvu ya nominal \(300~\text {W}\), frequency \(10^5~\text {Hz}\), intermittent coefficient 100 ndi \(200~\upmu \text {m}\ ) ya effective beam diameter.
Chithunzi 3 chikuwonetsa zotsatira za kuyerekezera kwa manambala kwa dera losungunuka pogwiritsa ntchito chitsanzo cha masamu cha macroscopic. M'mimba mwake mwa dera losakanikirana ndi \(200~\upmu \text {m}\) (\(100~\upmu \text {m}\) radius) ndi \(40~\upmu \text {m}\) kuya. Zotsatira za kuyerekezera zikuwonetsa kuti kutentha kwa pamwamba kumasiyana m'deralo ndi nthawi monga \(100~\text {K}\) chifukwa cha kuchuluka kwapakati kwa kusintha kwa pulse. Kuchuluka kwa kutentha \(V_h\) ndi kuzizira \(V_c\) kuli pa dongosolo la \(10^7\) ndi \(10^6~\text {K}/\text {s}\), motsatana. Ma mtengo awa akugwirizana bwino ndi kusanthula kwathu kwapitako64. Kusiyana kwa dongosolo la kukula pakati pa \(V_h\) ndi \(V_c\) kumabweretsa kutentha kwambiri kwa pamwamba, komwe kutentha kumapita ku substrate sikukwanira kuchotsa kutentha. Chifukwa chake, pa \(t=26~\upmu \text {s}\) kutentha kwa pamwamba kumafika pa \(4800~\text {K}\). Kutuluka kwa nthunzi mwamphamvu kwa zinthuzo kungayambitse kuti pamwamba pa chitsanzo pakhale kupanikizika kwambiri ndikuchotsedwa.
Zotsatira za kuyerekezera manambala za dera losungunuka la single laser pulse annealing pa mbale ya chitsanzo ya 316L. Nthawi kuyambira pachiyambi cha pulse mpaka kuya kwa dziwe losungunuka kufika pamtengo wapamwamba kwambiri ndi \(180~\upmu\text {s}\). Isotherm\(T = T_L = 1723~\text {K}\) ikuyimira malire pakati pa magawo amadzimadzi ndi olimba. Ma isobars (mizere yachikasu) amafanana ndi kupsinjika kwa yield komwe kumawerengedwa ngati ntchito ya kutentha mu gawo lotsatira. Chifukwa chake, pakati pa ma isolines awiri (isotherms\(T=T_L\) ndi isobars\(\sigma =\sigma _V(T)\)), gawo lolimba limakumana ndi katundu wamphamvu wamakaniko, zomwe zingayambitse kusintha kwa kapangidwe ka microstructure.
Zotsatirazi zafotokozedwanso mu Chithunzi 4a, komwe mulingo wa kupanikizika m'dera losungunuka umawonetsedwa ngati nthawi ndi mtunda kuchokera pamwamba. Choyamba, khalidwe la kupanikizika likugwirizana ndi kusintha kwa mphamvu ya kugunda kwa laser komwe kwafotokozedwa mu Chithunzi 2 pamwambapa. Kupanikizika kwakukulu \text{s}\) kwa pafupifupi \(10~\text {MPa}\) kunawonedwa pafupifupi \(t=26~\upmu). Chachiwiri, kusinthasintha kwa kupanikizika kwapafupi pamalo olamulira kuli ndi mawonekedwe ofanana a kugwedezeka monga kuchuluka kwa \(500~\text {kHz}\). Izi zikutanthauza kuti mafunde opanikizika a ultrasonic amapangidwa pamwamba kenako n'kufalikira mu substrate.
Makhalidwe owerengedwa a dera losinthika pafupi ndi dera losungunuka akuwonetsedwa mu Chithunzi 4b. Kuchotsa kwa laser ndi kupsinjika kwa thermoelastic kumapanga mafunde osinthika omwe amafalikira mu substrate. Monga momwe chithunzichi chikusonyezera, pali magawo awiri opanga kupsinjika. Pa gawo loyamba la \(t < 40~\upmu \text {s}\), kupsinjika kwa Mises kumakwera kufika pa \(8~\text {MPa}\) ndi kusintha kofanana ndi kuthamanga kwa pamwamba. Kupsinjika kumeneku kumachitika chifukwa cha kuchotsedwa kwa laser, ndipo palibe kupsinjika kwa thermoelastic komwe kunawonedwa m'malo owongolera chifukwa dera loyambirira lomwe linakhudzidwa ndi kutentha linali laling'ono kwambiri. Kutentha kukafalikira mu substrate, malo owongolera amapanga kupsinjika kwakukulu kwa thermoelastic pamwamba pa \(40~\text {MPa}\).
Magawo opsinjika omwe apezeka amakhudza kwambiri mawonekedwe olimba ndi madzi ndipo akhoza kukhala njira yowongolera yomwe imayang'anira njira yolimba. Kukula kwa dera losinthika ndi kokulirapo kawiri kapena katatu kuposa dera losungunuka. Monga momwe zasonyezedwera pa Chithunzi 3, malo a isotherm yosungunuka ndi mulingo wopsinjika wofanana ndi kupsinjika kwa yield akuyerekezeredwa. Izi zikutanthauza kuti kuwala kwa laser komwe kumayendetsedwa ndi pulsed kumapereka katundu wambiri wamakina m'malo omwe ali ndi mainchesi ogwira ntchito pakati pa 300 ndi \(800~\upmu \text {m}\) kutengera nthawi yomweyo.
Chifukwa chake, kusintha kovuta kwa pulsed laser annealing kumabweretsa zotsatira za ultrasonic. Njira yosankhira microstructure ndi yosiyana poyerekeza ndi SLM popanda ultrasound loading. Madera osakhazikika osinthika amachititsa kuti pakhale nthawi yozungulira ya compression ndi kutambasula mu gawo lolimba. Chifukwa chake, kupangidwa kwa malire atsopano a tirigu ndi malire a subgrain kumakhala kotheka. Chifukwa chake, mawonekedwe a microstructure amatha kusinthidwa mwadala, monga momwe zasonyezedwera pansipa. Zomaliza zomwe zapezeka zimapereka mwayi wopanga prototype ya SLM yoyendetsedwa ndi ultrasound. Pankhaniyi, piezoelectric inductor 26 yomwe imagwiritsidwa ntchito kwina ikhoza kuchotsedwa.
(a) Kupanikizika monga momwe nthawi imagwiritsidwira ntchito, komwe kumawerengedwa pa mtunda wosiyana kuchokera pamwamba 0, 20 ndi \(40~\upmu \text {m}\) motsatira mzere wa symmetry.(b) Kupsinjika kwa Von Mises komwe kumadalira nthawi kumawerengedwa mu matrix yolimba pa mtunda 70, 120 ndi \(170~\upmu \text {m}\) kuchokera pamwamba pa chitsanzo.
Kuyesera kunachitika pa mbale zachitsulo zosapanga dzimbiri za AISI 321H zokhala ndi miyeso \(20\times 20\times 5~\text {mm}\). Pambuyo pa laser pulse iliyonse, mbaleyo imayenda \(50~\upmu \text {m}\), ndipo chiuno cha laser pamwamba pa cholingacho chili pafupifupi \(100~\upmu \text {m}\). Mpaka ma beam pass asanu otsatira amachitidwa panjira yomweyo kuti apangitse kuti zinthu zomwe zakonzedwa zisungunuke kuti zikonzedwe. Nthawi zonse, malo osungunukawo amachitidwa sonicated, kutengera gawo la oscillatory la laser radiation. Izi zimapangitsa kuti dera la tirigu likhale locheperako kasanu. Chithunzi 5 chikuwonetsa momwe kapangidwe kake ka dera losungunuka ndi laser kamasinthira ndi kuchuluka kwa ma remelting cycles otsatira (ma passes).
Ma subplots (a,d,g,j) ndi (b,e,h,k) – kapangidwe kakang'ono ka madera osungunuka ndi laser, ma subplots (c,f,i,l) – kufalikira kwa tinthu tamitundu yosiyanasiyana m'derali. Kupaka mthunzi kumayimira tinthu tomwe timagwiritsidwa ntchito kuwerengera histogram. Mitundu imafanana ndi madera a tirigu (onani mzere wamitundu pamwamba pa histogram. Ma subplots (ac) amafanana ndi chitsulo chosapanga dzimbiri chosakonzedwa, ndipo ma subplots (df), (gi), (jl) amafanana ndi 1, 3 ndi 5 remelts.
Popeza mphamvu ya laser pulse sisintha pakati pa ma pass otsatira, kuya kwa malo osungunuka ndi komweko. Chifukwa chake, njira yotsatira "imaphimba" yonse yapitayo. Komabe, histogram ikuwonetsa kuti dera la pakati ndi lapakati la tirigu limachepa ndi kuchuluka kwa ma pass owonjezereka. Izi zitha kusonyeza kuti laser ikugwira ntchito pa substrate osati kusungunuka.
Kukonza tirigu kungayambitsidwe ndi kuzizira mwachangu kwa dziwe losungunuka65. Kuyesera kwina kunachitika pomwe pamwamba pa mbale zosapanga dzimbiri (321H ndi 316L) zidakumana ndi kuwala kwa laser kosalekeza mumlengalenga (Chithunzi 6) ndi vacuum (Chithunzi 7). Mphamvu yapakati ya laser (300 W ndi 100 W, motsatana) ndi kuya kwa dziwe losungunuka zili pafupi ndi zotsatira zoyesera za laser ya Nd:YAG mu free-running mode. Komabe, kapangidwe kabwino ka columnar kadawonedwa.
Kapangidwe kakang'ono ka dera losungunuka ndi laser la laser yopitilira mafunde (mphamvu yosasintha ya 300 W, liwiro la 200 mm/s scan, chitsulo chosapanga dzimbiri cha AISI 321H).
(a) Kapangidwe kakang'ono ndi (b) zithunzi za ma diffraction a ma electron backscatter a dera losungunuka ndi laser mu vacuum ndi laser yopitilira mafunde (mphamvu yosasintha ya 100 W, liwiro la scan la 200 mm/s, chitsulo chosapanga dzimbiri cha AISI 316L)\ (\sim 2~\text {mbar}\).
Chifukwa chake, zikuwonekeratu kuti kusintha kovuta kwa mphamvu ya laser pulse kumakhudza kwambiri kapangidwe kake. Tikukhulupirira kuti izi zimachitika chifukwa cha makina ndipo zimachitika chifukwa cha kupanga kugwedezeka kwa ultrasonic komwe kumafalikira kuchokera pamwamba pa radiation ya kusungunuka mozama kupita mu chitsanzo. Zotsatira zofananazo zidapezeka mu 13, 26, 34, 66, 67 pogwiritsa ntchito ma transducer akunja a piezoelectric ndi ma sonotrodes omwe amapereka ultrasound yapamwamba kwambiri muzinthu zosiyanasiyana kuphatikiza Ti-6Al-4V alloy 26 ndi chitsulo chosapanga dzimbiri 34 zotsatira zake. Njira yomwe ingatheke ikuganiziridwa motere. Ultrasound yayikulu ingayambitse cavitation ya acoustic, monga momwe zasonyezedwera mu ultrafast in situ synchrotron X-ray imaging. Kugwa kwa ma cavitation bubbles kumapanga mafunde owopsa muzinthu zosungunuka, zomwe kuthamanga kwake kutsogolo kumafika pafupifupi 100~\text {MPa}\)69. Mafunde owopsa oterewa akhoza kukhala olimba mokwanira kuti alimbikitse kupangidwa kwa critical-sized solid-phase nuclei mu bulk liquids, kusokoneza kapangidwe kabwino ka columnar grain ka Kupanga zowonjezera zamitundu yosiyanasiyana.
Pano, tikupereka njira ina yomwe imayang'anira kusintha kwa kapangidwe kake ndi sonication yamphamvu. Nthawi yomweyo pambuyo polimba, zinthuzo zimakhala pa kutentha kwambiri pafupi ndi malo osungunuka ndipo zimakhala ndi vuto lochepa kwambiri la zokolola. Mafunde amphamvu a ultrasonic angayambitse kuyenda kwa pulasitiki kusintha kapangidwe ka tirigu wa zinthu zotentha, zokhazikika. Komabe, deta yodalirika yoyesera pa kudalira kutentha kwa kupsinjika kwa zokolola ikupezeka pa \(T\lesssim 1150~\text {K}\) (onani Chithunzi 8). Chifukwa chake, kuti tiyese lingaliro ili, tinachita ma simulation a molecular dynamics (MD) a kapangidwe ka Fe-Cr-Ni kofanana ndi AISI 316 L steel kuti tiwone momwe kupsinjika kwa zokolola kumakhalira pafupi ndi malo osungunuka. Kuti tiwerenge kupsinjika kwa zokolola, tinagwiritsa ntchito njira ya MD shear stress relaxation yomwe yafotokozedwa mu 70, 71, 72, 73. Pa mawerengedwe a interatomic interaction, tinagwiritsa ntchito Embedded Atomic Model (EAM) kuchokera ku 74. Ma simulation a MD adachitika pogwiritsa ntchito ma LAMMPS codes 75,76. Tsatanetsatane wa ma simulation a MD adzafalitsidwa kwina. Zotsatira za mawerengedwe a MD a zokolola Kupsinjika maganizo monga momwe kutentha kumagwiritsidwira ntchito kwawonetsedwa mu Chithunzi 8 pamodzi ndi deta yoyesera yomwe ilipo ndi kuwunika kwina77,78,79,80,81,82.
Kupsinjika kwa zokolola za AISI grade 316 austenitic stainless steel ndi kapangidwe ka chitsanzo motsutsana ndi kutentha kwa ma simulation a MD. Miyeso yoyesera kuchokera ku maumboni: (a) 77, (b) 78, (c) 79, (d) 80, (e) 81. onani.(f)82 ndi chitsanzo choyesera cha kudalira kwa zokolola za zokolola za kutentha kwa kuyeza kupsinjika kwa mzere panthawi yopanga zowonjezera zothandizidwa ndi laser. Zotsatira za ma simulation akuluakulu a MD mu kafukufukuyu zawonetsedwa ngati \(\vartriangleleft\) ya kristalo imodzi yopanda chilema ndi \(\vartriangleright\) ya tirigu wocheperako poganizira kukula kwa tirigu wapakati kudzera mu Hall-Petch relation Dimensions\(d = 50~\upmu \text {m}\).
Zikuoneka kuti pa \(T>1500~\text {K}\) kupsinjika kwa zokolola kumatsika pansi pa \(40~\text {MPa}\). Kumbali inayi, kuyerekezera kumaneneratu kuti kuchuluka kwa ma ultrasonic komwe kumapangidwa ndi laser kumaposa \(40~\text {MPa}\) (onani Chithunzi 4b), chomwe chimakwanira kuyambitsa kuyenda kwa pulasitiki mu zinthu zotentha zomwe zangouma kumene.
Kapangidwe ka microstructure ka 12Cr18Ni10Ti (AISI 321H) austenitic stainless steel panthawi ya SLM kanafufuzidwa mwachisawawa pogwiritsa ntchito gwero la laser lopangidwa ndi mphamvu yosinthasintha.
Kuchepa kwa kukula kwa tirigu m'dera losungunuka ndi laser kunapezeka chifukwa cha kusungunuka kosalekeza kwa laser pambuyo pa 1, 3 kapena 5.
Kujambula zithunzi pogwiritsa ntchito macroscopic kumasonyeza kuti kukula koyerekeza kwa dera komwe kusintha kwa ma ultrasonic kungakhudze bwino kutsogolo kwa kulimba kuli mpaka \(1~\text {mm}\).
Chitsanzo cha MD cha microscopic chikuwonetsa kuti mphamvu ya AISI 316 austenitic stainless steel yachepa kwambiri kufika pa \(40~\text {MPa}\) pafupi ndi malo osungunuka.
Zotsatira zomwe zapezeka zikusonyeza njira yowongolera kapangidwe ka zinthu pogwiritsa ntchito njira zovuta zosinthira laser ndipo zitha kukhala maziko opanga zosintha zatsopano za njira ya pulsed SLM.
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