2Si2相可以作為初生Mg2Si的異質(zhì)形核核心，使初生Mg2Si細(xì)化。Ba-Nd復(fù)合變質(zhì)是通過在Mg-3Si-4Zn-1.2Ba合金中加入變質(zhì)劑Nd來(lái)完成的。通過Miedema模型和對(duì)吉布斯自由能的線性擬合，發(fā)現(xiàn)由于Nd和/或Ba原子能與Si原子形成更加穩(wěn)定的化合物NdSi、NdSi2、Ba2Si、BaSi2，防止Si原子在凝固的初始階段與Mg原子結(jié)合，因此初生Mg2Si的生長(zhǎng)速度被抑制，微觀結(jié)構(gòu)中初生Mg2Si相變小。當(dāng)Nd含量為2.0%時(shí)，Ba-Nd復(fù)合變質(zhì)效果最好，即初生Mg2Si由平均面積約為 600 μm2 的樹枝狀變?yōu)槠骄呴L(zhǎng)約5 μm的近似方形的組織，共晶Mg2Si由平均面積約444 μm2 的復(fù)雜粗大漢字狀變?yōu)槠骄娣e約89 μm2的簡(jiǎn)單漢字狀組織。合金硬度由575.75 MPa提高到612.11 MPa，提高了6.31%。;The effects of Ba-Nd composite modification on the microstructure and mechanical properties of Mg-3Si-4Zn cast alloy were investigated. The microstructure was characterized by OM, SEM, EDS and XRD. The mechanical properties were tested by hardness test. The best modification effect was achieved when a single denaturant Ba of 1.2wt% was added to the Mg-3Si-4Zn alloy. Results show that the formed phase BaMg2Si2 can act as a heterogeneous nucleation core for the primary Mg2Si, refining the primary Mg2Si. Ba-Nd composite modification is achieved by adding the modifier Nd to the Mg-3Si-4Zn-1.2Ba alloy. By the calculation of the Gibbs free energy using the Miedema model and a linear fit, it is found that the growth rate of primary Mg2Si is suppressed and the primary Mg2Si phase in the microstructure becomes smaller because more stable compounds like NdSi, NdSi2, Ba2Si, and BaSi2 can be formed by Nd and/or Ba atoms with Si atoms, preventing Si atoms from binding to Mg atoms at the initial stage of solidification. The best Ba-Nd composite modification effect is achieved when the Nd content is 2.0wt%, i.e. the primary Mg2Si changes from a dendritic shape with an average area of about 600 μm2 to a nearly square-shape with an average side length of about 5 μm and the eutectic Mg2Si changes from complex and coarse Chinese-script shape with an average area of about 444 μm2 to simpler shape with a mean area of about 89 μm2. The hardness of the alloy is increased from 575.75 MPa to 612.11 MPa, increased by 6.31%."/>
2Si;Ba-Nd復(fù)合變質(zhì);組織;硬度;Miedema模型;Mg-Si-Zn alloy;Mg2Si;Ba-Nd composite modification;microstructure;hardness;Miedema model"/>