Fatigue Resistance thiab Grain Size ntawm Nickel Alloys - Kev Paub

Qhov cuam tshuam ntawm grain loj rau qaug zog tawg pib

Kev qaug zog ntawm cov npib tsib xee - raws li cov alloys feem ntau yog los ntawm qhov chaw los yog subsurface stress concentration cheeb tsam, xws li grain ciam teb, inclusions, thiab machining defects.

Raunplua - grained npib tsib xee - raws li alloys, tus naj npawb ntawm grain ciam teb ib unit volume nce ho. Grain ciam teb ua raws likev cuam tshuam zoo rau kev txav mus los: thaum cyclic kev nyuaj siab yog siv, dislocations sau nyob rau hauv grain ciam teb es tsis txhob tsim loj - scale slip bands (uas yog lub ntsiab qhov chaw ntawm qaug zog tawg pib). Lub caij no, cov nplej zoo tuaj yeem cuam tshuam cov kev ntxhov siab hauv zos, txo qhov tshwm sim ntawm tawg nucleation thiab yog li txhim kho covqaug zog txwvthiabsiab - lub voj voog qaug zog (HCF) tsis kamntawm lub alloy.

Raucoarse - grained npib tsib xee - raws li alloys, qhov tsawg ntawm cov qoob loo ciam teb ua rau yooj yim tsim ntawm nruam plam bands hauv cov nplej nyob rau hauv cyclic loading. Cov hlua khi no yuav ua rau cov yas deformation thiab micro - tawg ntawm cov hlau nplaum, ua rau kom qaug zog tawg pib. Yog li ntawd, ntxhib - grained alloys feem ntau pom qis siab - lub voj voog qaug zog.

Cov nyhuv ntawm grain loj rau qaug zog tawg propagation

Cov txheej txheem nthuav tawm ntawm qaug zog tawg yog muab faib ua ob theem: lubtheem I (transgranular lossis intergranular qeeb propagation)thiabtheem II (hloov transgranular propagation).

Nyob rau theem kuv, rau qhov zoo - grained alloys, tawg yuav tsum tsis tu ncua hloov propagation paths thaum hla ntau grain ciam teb, uas siv ib tug loj npaum li cas ntawm tawg zog thiab slows down lub propagation tus nqi. Rau ntxhib - grained alloys, cov kab nrib pleb tuaj yeem nthuav tawm raws li kev taw qhia hauv cov nplej loj uas tsis muaj zog, ua rau kev nthuav tawm sai dua.

Hauv theem II, kev nthuav tawm ntawm kev qaug zog tawg yog dominated los ntawm kev ntxhov siab siv zog. Nyob rau lub sijhawm no, kev cuam tshuam ntawm cov qoob loo tsis muaj zog, tab sis cov nplej nplua nuj tseem muaj qee qhov zoo dua hauv kev ua kom qeeb tawg tawg piv nrog cov nplej ntxhib. Txawm li cas los xij, yog tias cov qoob loo me me dhau lawm, qhov kev faib ua feem ntawm cov ciam teb nce ntxiv, uas tuaj yeem ua rau muaj kev cuam tshuam ntawm intergranular brittleness nyob rau hauv qee qhov kev ntxhov siab thiab cuam tshuam ib feem ntawm kev qaug zog kev txhim kho.

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Cov xwm txheej tshwj xeeb nyob rau hauv siab - kub thiab siab - kev ntxhov siab

Nickel - raws li alloys yog dav siv nyob rau hauv siab - kub ib puag ncig (xws li aero - cav turbine hniav). Nyob rau hauv siab - kub thiab qis - lub voj voog qaug zog (LCF) cov xwm txheej, kev sib raug zoo ntawm cov nplej loj thiab qaug zog hloov pauv:

Fine - grained alloys yog nquaggrain ciam swbntawm qhov kub thiab txias, uas accelerates qaug zog tsis ua hauj lwm.

Nruab nrab ntxhib - grained alloys muaj kev tiv thaiv zoo dua rau cov ciam teb zawv zawg, yog li lawv qhov qis - lub voj voog qaug zog ua haujlwm zoo dua li qhov zoo - grained alloys hauv qhov xwm txheej no.

Optimal grain loj ntau rau kev siv tswv yim

Tsis muaj qhov "zoo tshaj" grain loj rau nickel - raws li alloys. Qhov zoo tshaj plaws grain loj yog txiav txim los ntawm lubkev pabcuam:

Rau cov khoom raug rau qis - kev ntxhov siab thiab siab - lub voj voog qaug zog (piv txwv li, cov qauv ntawm cov roj turbines), anplua - grained qauv(grain size grade 6–8) yog qhov zoo dua los ua kom qhov kev qaug zog ntau tshaj plaws.

Rau cov khoom raug rau siab - kub thiab qis - voj voog qaug zog (xws li, turbine hniav), ame ntsis ntxhib - grained qauv(grain size grade 2–4) yog qhov tsim nyog rau qhov sib npaug siab - qhov kub thiab txias zog thiab qaug zog tawg propagation kuj.

Hauv cov ntsiab lus, qhov qaug zog tsis kam ntawm npib tsib xee - raws li cov alloys tsis yog qhov zoo lossis tsis zoo cuam tshuam nrog cov nplej loj. Nws yog ib qho txiaj ntsig zoo cuam tshuam los ntawm cov qoob loo ciam teb ntom ntom, theem kev ntxhov siab, kev pabcuam kub, thiab cov yam ntxwv ntawm lub voj voog thauj khoom. Kev tswj hwm ntawm cov qoob loo loj los ntawm cov txheej txheem kho cua sov yog tus yuam sij rau kev ua kom lub zog qaug zog ntawm nickel - raws li cov alloys.