3473

3279

كارشناسي ارشد

شناسايي، انتخاب و روش ساخت مواد فلزي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1385

نه، 112، [II] ص.: مصور، جدول، نمودار

ص. ع. به فارسي و انگليسي

بهزاد نيرومند

15/2/86

مسعود پنجه پور، ايوب حلوائي

مهندسي مواد

ID3279

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

AbstractThe basis of SSM structure developement in SSR process is creating an environmentwhere copious nucleation can occur during the early stages of solidification Underthis situation the growth of the particles became limited since there is simply nospace available for the particles to grow into For this reason the particles havelimited and more stable growth which facilitate the non dendritic structure formationin the short times In this study effects of casting parameters upon rheocast structure of Al 7 1wt Siproduced by SSR process were examined The experimental results shown that non dendritic structure formed after stiiring below liquidus temperature for a matter ofseconds and increasing the stirring time had little impact on final morphology ofprimary particles Moreover stirring has shown that to be affecting the averegeparticles size and its mainly influence is in the initial stage of solidification which through increasing the concentration gradient in front of s l interface creat moredriving force for particles growth the primary particles morphology has also beshown to be insensitive to large variations in stiiring speed but the data indicated thatthe shape and size of primary particles became more uniform when the materialprocessed with higher stirring speeds The results indicated that for a given secondary cooling rate the primary particles inhigh solid fraction SSR slurries grow less significantly after casting than those in lowsolid fractions The shape factor of primary particles also depends on secondarycooling rate Increasing the secondary cooling rate causes the shape factor to decrease Effects of secondary cooling rate on rheocast structure was shown that decreasing thesecondary cooling rate not only cause the shape factor of particles to increase but alsoincreases the agglomeration size These effects can be explained based on variation of nucleation rate particles density local solidification time overlap of diffusion boundary layer concentration gradientof solute in front of solidification interface and ripening of primary particles

بهزاد نيرومند

مسعود پنجه پور، ايوب حلوائي