制備AM60鎂合金半固態(tài)漿料的影響(Ⅲ)
(1. 蘭州理工大學(xué) 甘肅省有色金屬新材料省部共建國(guó)家重點(diǎn)實(shí)驗(yàn)室，蘭州 730050；
2. 蘭州理工大學(xué) 有色金屬合金及加工教育部重點(diǎn)實(shí)驗(yàn)室，蘭州 730050)
摘 要: 采用自孕育鑄造法制備AM60鎂合金半固態(tài)坯料，研究導(dǎo)流器參數(shù)對(duì)半固態(tài)組織的影響規(guī)律及組織形成機(jī)理。結(jié)果表明：導(dǎo)流器能有效促進(jìn)合金組織由樹(shù)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(shí)，導(dǎo)流器的相關(guān)參數(shù)，如角度、長(zhǎng)度、溫度、混合段的凹槽寬度，均影響合金的傳熱及流動(dòng)，進(jìn)而影響其凝固組織；在導(dǎo)流器角度為30°～45°、長(zhǎng)度為500 mm、混合段凹槽寬度為50 mm、且通水冷卻時(shí)可以獲得細(xì)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(dǎo)流器出口寬度有利于增強(qiáng)液體紊流，促進(jìn)晶粒均勻分布；導(dǎo)流器促進(jìn)了熔體非均質(zhì)形核及激冷晶的形成，增強(qiáng)了晶粒增殖；熔體對(duì)流使合金的溫度場(chǎng)和濃度場(chǎng)更均勻，晶粒生長(zhǎng)以顆粒狀生長(zhǎng)、薔薇晶根部頸縮熔斷和磨圓熟化機(jī)制為主。
關(guān)鍵字: AM60鎂合金；自孕育法；半固態(tài)漿料；非枝晶；形核；生長(zhǎng)
prepared by self-inoculation method (Ⅲ)
（1. State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials,
Lanzhou University of Technology, Lanzhou 730050, China;
2. Key Laboratory of Non-ferrous Metal Alloys and Processing, Ministry of Education,
Lanzhou University of Technology, Lanzhou 730050, China）
Abstract: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.
Key words: AM60 magnesium alloy; self-inoculation method; semi-solid slurry; non-dendritic; nucleation; growth
