nilt75gtalltxgtvlt25xgt合金沉淀行为的微观相场模拟

《nilt75gtalltxgtvlt25xgt合金沉淀行为的微观相场模拟》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。

1、摘要.曰..............摘要本文以Ni-AI-V合金为对象，首次采用微观相场法系统研究了温度、浓度对成核孕育期、沉淀序列、沉淀机制的影响规律，以及有序畴界面结构、界面迁移性、形核取向性。随温度降低，丫相和e相的形核孕育期缩短、形核率提高和长大速度加快。随Al浓度减小，两相的孕育期延长;沉淀序列由0相先析出，过渡到e相和丫相同时析出，再过渡到犷相先出现。得出了沉淀机制对温度、浓度的响应关系。随温度降低，Ni75Al4.5V20，合金的。相沉淀由非经典形核机制向等成分有序化+失稳分解机制转变，Y'相沉淀由异相非经典形核机制向非

2、经典形核+失稳分解机制转变;Ni75Als.5Vis.5合金的0相的沉淀机制由非经典形核+失稳分解向非经典形核转变，了相的沉淀机制由异相非经典形核+失稳分解向等成分有序化十失稳分解逐渐转变;Ni75A17.5V17.5合金的e相的沉淀为异相非经典形核机制，丫相沉淀机制从非经典形核十失稳分解转变为等成分有序化+失稳分解。y'(L12)相之间、0(D022)相之间、y'(L12)与0(D022)相之间分别有三种、八种、四种界面结构，根据界面的相对关系和界面结构，又可分为可迁移界面和不动界面，并对界面演化和界面处析出有重大影响，沿[0101

3、0方向(004)o与(001)0面相遇，有序相界面重新溶解为无序区，(001)0与(001)0面相遇，界面处可析出丫相。Y'(L12)相和9(D022)相在有序界面的形核位置和生长方向具有择优取向性。关键词:微观相场，温度，沉淀，界面，模拟AbstractAbstractTheregulationofincubationtime,precipitationsequenceandmechanismofNi-AI-Valloyontheefectoftemperatureandconcentrationwasfirststudiedusi

4、ngthemicroscopicphase-fieldmethod,andtheinterphaseboundarystructureofordereddomain,migrationcharacteristicofinterphaseboundaryandnucleationorientationwasinvestigated.Asthetemperaturelower,theincubationtimeofthe丫phaseand0phaseisshortenandthenucleationratioincreaseandtheg

5、rowthvelocityquicken.TheincubationtimeprolongwiththeminishofAlconcentration,andthetransitionoftwophasesfromephaseformsfirstlyto0phaseandy'phaseformsimultaneouslyandthentoy'phaseformsfirstly.Thecorrelationbetweenprecipitationmechanismandtemperatureandconcentrationwasdemo

6、nstrated.Asthetemperaturelower,theprecipitationmechanismof0phaseofNi75A14.5Vzo.5alloytransformfromnon-classicalnucleationtocongruentordering+spinodaldecomposition,andthey'phasetransformfromnon-classicalnucleationtothemixedstyleofnon-classicalnucleation+spinodaldecomposi

7、tion.TheprecipitationmechanismofophaseofNi75Al6.5V1s.5alloytransformfromnon-classicalnucleation+spinodaldecompositiontonon-classicalnucleation,andthey'phasetransformfromnon-classicalnucleation+spinodaldecompositiontocongruentordering+spinodaldecomposition.Theprecipitati

8、onmechanismof0phaseofNi75A17.5V17.5alloyisnon-classicalnucleation,andthey'phasetransformfromnon-classicalnucle