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導流器對自孕育鑄造法制備AM60鎂合金半固態(tài)漿料的影響(Ⅲ)
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更新時間：2015-09-19
采用自孕育鑄造法制備AM60鎂合金半固態(tài)坯料，研究導流器參數(shù)對半固態(tài)組織的影響規(guī)律及組織形成機理。
導流器對自孕育鑄造法制備AM60鎂合金半固態(tài)漿料的影響(Ⅲ)Effect of cooling channel on AM60 Mg alloy semi-solid slurry?prepared by self-inoculation method (Ⅲ)
采用自孕育鑄造法制備AM60鎂合金半固態(tài)坯料，研究導流器參數(shù)對半固態(tài)組織的影響規(guī)律及組織形成機理。結(jié)果表明：導流器能有效促進合金組織由樹枝晶向等軸晶及顆粒狀晶的轉(zhuǎn)變；熔體處理溫度和孕育劑加入量一定時，導流器的相關(guān)參數(shù)，如角度、長度、溫度、混合段的凹槽寬度，均影響合金的傳熱及流動，進而影響其凝固組織；在導流器角度為30°～45°、長度為500 mm、混合段凹槽寬度為50 mm、且通水冷卻時可以獲得細小顆粒狀或薔薇狀的半固態(tài)坯料，初生α-Mg的平均晶粒尺寸為37.5 μm；減小導流器出口寬度有利于增強液體紊流，促進晶粒均勻分布；導流器促進了熔體非均質(zhì)形核及激冷晶的形成，增強了晶粒增殖；熔體對流使合金的溫度場和濃度場更均勻，晶粒生長以顆粒狀生長、薔薇晶根部頸縮熔斷和磨圓熟化機制為主。
The semi-solid slurry of AM60 Mg alloy was prepared by a novel self-inoculation method (SIM). The effects of the cooling channel parameters on the microstructure and microstructure formation mechanism were investigated. The results show that cooling channel can promote the microstructure evolution from coarser dendrite to rosette or small block. At the constant value of melt treatment temperature and addition amount of self-inoculants, the parameters of fluid director, such as slope angle, length, temperature and width of exit, have influence on the heat extraction and shear intensity of melt flow, and finally affect the solidification microstructure. When the cooling channel parameters are set at angle between 30°?45°, length of 500 mm, width of exit of 50 mm and water cooled at the bottom, the semi-solid billet with refined rosette or small block microstructure is produced, and the average grain size is 37.5 μm. The decrease of the exit width leads to uniform distribution of grains. The cooling channel enhances the heterogeneous nucleation and formation of chill grains, which results in a high grain density. The melt convection leads to uniform distribution of temperature and solute field in bulk melt. The granular and rosette-like growth and the ripening of grains are the main growth mechanism.
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