Mg70Ni15Gd10Ag5块体非晶的制备及晶化行为

采用铜模铸造法制备新型块体非晶合金Mg70Ni15Gd10Ag5(at%)，其临界制备尺寸不低于5 mm，是目前Mg-Ni基非晶合金制备尺寸的最大值。采用差示扫描量热（DSC）法研究非晶合金的晶化行为，发现合金的晶化为多级晶化。随着升温速度的提高，玻璃转变温度Tg、晶化开始温度Tx、熔化前4个放热峰温度（Tp1、Tp2、Tp3、Tp4）、熔化开始温度（Tm）和液相线温度（Tl）均向高温区移动，晶化行为具有显著的动力学特征。利用Kissinger法计算特征温度对应的激活能，其值分别为Eg=188.05 kJ/mol、Ex=144.79 kJ/mol、Ep1=138 kJ/mol、Ep2=142.40 kJ/mol、Ep3=119.10 kJ/mol、Ep4=72.86 kJ/mol。

Preparation of Mg70Ni15Gd10Ag5 Bulk Amorphous Alloys and Their Crystallization Behaviors

A novel bulk amorphous alloy Mg70Ni15Gd10Ag5 (at%)was prepared by copper-mold casting, and its critical size was no less than 5 mm, which is the largest value of preparation size for Mg-Ni based alloys at present. The crystallization behavior of the bulk amorphous alloy during continuous heating was studied by differential scanning calorimeter (DSC). Results show that the crystallization of the amorphous alloy is multiple. With increasing of the heating rate, all the characteristic temperatures including glass transition temperature Tg, onset crystallization temperature Tx, peak crystallization temperatures Tp (Tp1, Tp2, Tp3 and Tp4), melting-starting temperature Tm and liquidus temperature Tl shift to higher temperatures. The crystallization has remarkable dynamic characteristics. The activation energies Eg, Ex and Ep, corresponding to characteristic temperatures Tg, Tx and Tp were obtained by Kissinger equation, as Eg=188.05 kJ/mol, Ex=144.79 kJ/mol, Ep1=138 kJ/mol, Ep2=142.40 kJ/mol, Ep3=119.10 kJ/mol and Ep4=72.86 kJ/mol.