1. Kev qaug zog ntawm Titanium Alloys
Cov yam ntxwv tseem ceeb ntawm Titanium Alloy Fatigue Strength
Rau annealed Ti-6Al-4V (qhov feem ntau titanium alloy), chav kub kub qaug zog (ntawm 10⁷ cycles, R=-1, qhov twg R yog qhov kev ntxhov siab ntawm qhov tsawg kawg nkaus rau qhov siab tshaj plaws) muaj nyob ntawm300-400 MPa, nrog qee qhov cua sov- kho qhov sib txawv mus txog 450-500 MPa. Qhov no yog qhov siab dua li ntawm 304 stainless hlau (≈170 MPa) thiab 6061-T6 aluminium (≈90 MPa) raws li tib yam kev sim, ua Ti-6Al-4V zoo tagnrho rau kev siv lub voj voog siab (HCF).
Rau siab -lub zog titanium alloys (piv txwv li, Ti-6Al-2Sn-4Zr-2Mo, Ti-5Al-2.5Sn), qaug zog zog tuaj yeem tshaj 500 MPa hauv cov tshuaj kho thiab hnub nyoog (STA) lub xeev, raws li cov theem zoo precipitated hauv lawv cov microstructure impede pib tawg.
Dual-phase (+) alloys (piv txwv li, Ti-6Al-4V): Lawv qhov sib npaug / microstructure muab kev pom kev qaug zog. Lub -theem pab txhawb lub zog thiab tawg kev tawm tsam, thaum lub sijhawm -theem txhim kho ductility thiab inhibits qhov pib tawg. Tshaj- kev laus lossis kev ua haujlwm txias heev, txawm li cas los xij, tuaj yeem coarsen -theem hais los yog qhia cov kev ntxhov siab uas seem, txo qis qaug zog los ntawm 10–20%.
alloys (piv txwv li, Ti-5Al-2.5Sn): Cov alloys muaj qhov ua tau zoo qis - voj voog qaug zog (LCF) kev ua haujlwm vim lawv ruaj khov HCP -theem microstructure, nrog LCF lub neej (ntawm Δσ/2=500} MPa) tshaj 10⁴ cycles. Lawv tau dav siv nyob rau hauv qis -kub aerospace Cheebtsam.
alloys (piv txwv li, Ti-10V-2Fe-3Al): Nrog rau tag nrho BCC -theem qauv, cov alloys muaj siab qaug zog tawg kev loj hlob kuj (da/dN ≈ 10⁻⁸ m/cycle ntawm ΔK=20 MPa·m¹/²) thiab tsim nyog rau cov khoom nyob rau hauv dynamic, siab - load tej yam kev mob (piv txwv li, helicopter rotor ncej).
Corrosive environmental fatigue (CAF): Hauv dej hiav txwv lossis chloride- muaj cov xov xwm, titanium alloys tswj kev qaug zog zoo dua li cov hlau los yog txhuas, vim tias lawv cov yeeb yaj kiab oxide passive tiv thaiv corrosion-induced tawg pib. Ti-6Al-4V lub zog qaug zog hauv dej hiav txwv tsuas yog txo los ntawm 5-10% (rau ≈350 MPa ntawm 10⁷ cycles), hos 304 stainless hlau ntsib 50% poob vim pitting corrosion.
Nto moo mob rhiab heev: Deg tsis xws luag (piv txwv li, machining marks, microcracks) thiab hydrogen contamination yog qhov ua rau qaug zog loj. Txhaj peening los yog anodizing tuaj yeem txhim kho qaug zog ntawm 20-30% los ntawm kev qhia txog cov kev ntxhov siab uas nyob ruaj khov thiab txhim kho qhov chaw passivation. Hloov pauv, hydrogen embrittlement tuaj yeem txo qhov qaug zog lub neej txog li 50% los ntawm kev txhawb nqa kev loj hlob ntawm intergranular tawg ntawm qhov kub thiab txias.
Ntawm qhov kub thiab txias (piv txwv li, -196 degree), Ti-6Al-4V lub zog qaug zog nce mus rau450-500 MPavim muaj kev txhim kho atomic bonding thiab txo qis kev txav mus los, tsis muaj ductile - mus rau - kev hloov pauv hauv kev qaug zog.
Ntawm qhov kub siab (txog 300 degree), nws lub zog qaug zog tseem siab tshaj 250 MPa (10⁷ cycles), tab sis siab tshaj 400 degree, oxidation thiab grain ciam softening ua rau poob sai (poob 30-40% ntawm chav tsev-kub qaug zog ntawm 500 degree).
2. Creep Properties ntawm Titanium Alloys
Cov yam ntxwv tseem ceeb ntawm Titanium Alloy Creep Performance
+ alloys (piv txwv li, Ti-6Al-4V): Lawv qhov siab tshaj plaws ntev -lub sij hawm creep kev pabcuam kub yog300-350 degree. Ntawm 300℃thiab 200 MPa kev ntxhov siab, qhov ruaj khov- lub xeev creep tus nqi tsawg dua lossis sib npaug li 10⁻⁸ s⁻¹, thiab creep deformation tsawg dua 0.1% tom qab 10,000 teev ntawm raug- txaus rau lub dav hlau cav compressor hniav nyob rau hauv substructor cov khoom. Tshaj 400 degree, qhov nkag nrawm nrawm nrawm (dhau 10⁻⁶ s⁻¹ ntawm 450℃/ 200 MPa) vim yog -theem coarsening thiab grain ciam swb.
alloys (piv txwv li, Ti-5Al-2.5Sn, Ti-6Al-2Sn-4Zr-2Mo): Cov alloys no muaj qhov nkag siab tshaj plaws ntawm cov titanium alloys, nrog rau lub sijhawm ntev - qhov kev pabcuam kub ntawm400-500 degree. Piv txwv li, Ti-6Al-2Sn-4Zr-2Mo ntawm 450℃thiab 250 MPa muaj tus nqi qis qis qis dua los yog sib npaug rau 5 × 10⁻⁹ s⁻¹ thiab lub neej tawg ntau tshaj 100,000 teev, ua rau nws haum rau qhov chaw siab.
alloys: Lawv cov creep kuj yog qis dua thiab + alloys, nrog rau qhov siab tshaj plaws kev pab cuam kub ntawm 300-350 degree, raws li BCC -theem muaj ntau dua atomic zog thiab yog nquag mus deformation nyob rau hauv ntev - kev nyuaj siab.
Ntawm qhov kub thiab txias (<400°C) and high stresses, creep is dominated by dislocation nce thiab glidenyob rau hauv -theem, nrog rau -theem ua raws li ib tug barrier rau dislocation txav (txhim kho creep kuj nyob rau hauv dual-phase alloys).
At high temperatures (>450 degree),grain ciam zawv zawg thiab diffusion creepua tus tseem ceeb. alloys nrog nplua, uniformly faib nplej thiab cov khoom- kev daws teeb meem - muaj zog cov ntsiab lus (Al, Sn, Zr) tiv taus grain ciam zawv zawg zoo, li no lawv superior siab - kub creep kev ua tau zoo.
Kev kho cua sov ua lub luag haujlwm tseem ceeb: Kev daws teeb meem ua raws li kev laus (STA) rau + alloys precipitates fine -phase particles nyob rau hauv -matrix, uas pin dislocations thiab txo tus nqi nkag los ntawm 50-70% piv rau lub xeev annealed.
Hauv cov huab cua oxidizing, tsim kom muaj cov tuab tuab TiO₂-Al₂O₃ passive zaj duab xis ntawm titanium alloys (tshwj xeeb tshaj yog cov ntsiab lus Al siab) inhibits oxygen diffusion thiab txo cov creep embrittlement. Txawm li cas los xij, ntawm qhov kub siab tshaj 550 degree, oxide zaj duab xis yuav ntxeem tau, tso cai rau cov pa oxygen nkag mus rau hauv matrix thiab tsim ib qho "alpha case," uas ua rau cov pob txha tawg.
Hauv hydrogen- muaj ib puag ncig, hydrogen nqus tau nce tus nqi nkag los ntawm kev txhawb nqa kev txav mus los thiab kev sib tsoo ntawm qhov sib tsoo, txwv txoj kev siv lub neej ntawm titanium alloys hauv cov huab cua li 20-30%.
