CAJ | 학술논문

为了研究触变注射成形AZ91D合金中固相颗粒的形貌演变和液相的凝固行为,对该合金的组织和凝固行为进行了试验观察和理论分析.典型触变注射成形AZ91D合金由α-Mg和β-Mg17Al12两相构成,α-Mg相又可分为未熔固相和初生固相.未熔固相主要有形貌较为接近球状的固相、形貌不规则的固相、内部含有小液池的固相以及包裹液相的固相4种形貌.形貌不规则的固相被认为是球状固相和包裹液相的固相的中间发展形貌,内部含有小液池的固相可能是包裹液相的固相的初级形貌,包裹液相的固相则可能发生破裂形成不规则固相,最终发展成球状固相.球状固相被认为是最理想的也是最终的固相形貌.初生固相在液相合金中形核并长大,直至有不稳定长大行为发生为止,较为细小、圆整,主要受冷却速率的影响.Mg-Al合金二元相图的分析结果与试验观察到的组织相吻合.
위료연구촉변주사성형AZ91D합금중고상과립적형모연변화액상적응고행위,대해합금적조직화응고행위진행료시험관찰화이론분석.전형촉변주사성형AZ91D합금유α-Mg화β-Mg17Al12량상구성,α-Mg상우가분위미용고상화초생고상.미용고상주요유형모교위접근구상적고상、형모불규칙적고상、내부함유소액지적고상이급포과액상적고상4충형모.형모불규칙적고상피인위시구상고상화포과액상적고상적중간발전형모,내부함유소액지적고상가능시포과액상적고상적초급형모,포과액상적고상칙가능발생파렬형성불규칙고상,최종발전성구상고상.구상고상피인위시최이상적야시최종적고상형모.초생고상재액상합금중형핵병장대,직지유불은정장대행위발생위지,교위세소、원정,주요수냉각속솔적영향.Mg-Al합금이원상도적분석결과여시험관찰도적조직상문합.
Experimental investigation and theoretical analysis of the microstructure of thixomolded AZ91D were carried out to comprehensively understand the morphology transformation of solid particles and the solidification behavior.Typical microstructure of thixomolded AZ91D is composed of α-Mg and β-Mg17Al12,characterized with αun,αprim and eutectic.Four kinds of αun are classified according to the morphology and generation mechanism,such as spherical (α1),irregular (α2),entrapping liquid alloy inside (α3) and entrapping pool inside (α4).Under the effect of heating,shearing,collision,agglomeration or fragmentation,α2 and α4can be the middle states of α1 and α3.Similarly,α4 and α3 can also break into a2 and become a1 at the end.Controlled by undercooling,αprim nucleates and spherically grows within the remaining liquid alloy of thixomolded AZ91D until instability growth.The investigated microstructure was theoretically proved according to the analysis of Mg-A1 binary phase diagram.