超重力场与钠盐变质对Al-12Si合金共晶组织及硬度的影响

Effects of Super-gravity Field and Sodium Salt Metamorphism on Eutectic Structure and Hardness of Al-12Si Alloy

利用离心机研究了超重力场对未变质及经钠盐变质的Al-12Si合金共晶组织及显微硬度的影响。结果表明,超重力场可使未变质Al-12Si合金心部共晶Si显著细化和颗粒化,且在4 000g(g=9.8 m/s^2)超重力场下凝固时效果最好,此时心部共晶Si大部分呈颗粒状,直径约为0.7μm;而经钠盐变质合金在超重力场下凝固时,心部共晶Si细化和颗粒化程度更高,且在超重力场达到3 000g时效果最佳,此时心部共晶Si基本为颗粒状,直径约为0.3μm;随重力场加大,未变质合金心部硬度(HV)逐渐提高,在4 000g时达到最大值72;而经钠盐变质合金在超重力场下凝固时心部硬度(HV)提高更为明显,且在3 000g时达到最大值88。

The effects of super-gravity field on the eutectic microstructure and microhardness of Al-12 Si alloy without modification and with sodium modification were investigated by centrifuge.The results reveal that,the central eutectic silicon in the un-modified Al-12 Si alloy can be refined significantly and granulated in the super-gravity field,and most of the central eutectic silicon presents granular with a diameter of about 0.7μm with solidified at 4 000 g（g=9.8 m/s^2）.In addition,the central eutectic silicon can be refined and granulated to a higher degree under compound action of super-gravity field and sodium salt metamorphism,and the central eutectic silicon is basically granular with a diameter of about 0.3μm when the super-gravity field reaches 3 000 g.With the increase of gravity field,the central hardness（HV）of the un-modified alloy is increased gradually and reaches the maximum value of 72 at 4 000 g.The central hardness（HV）is increased more obviously when the sodium salt metamorphic alloy is solidified in the super-gravity field and reaches the maximum value of 88 at 3 000 g.