Cu_(46)Zr_(44)Al_5Nb_5块体非晶合金的晶化行为研究

Crystallization Behavior of Cu_(46)Zr_(44)Al_5Nb_5 Bulk Amorphous Alloy

通过磁悬浮熔炼-水冷铜模吸铸法制备了Cu46Zr44Al5Nb5块体非晶合金,并研究其变温晶化行为和等温晶化行为,运用Kissinger法和FWO法分别计算出各特征激活能和阶段激活能,考察了不同加热速度下晶化体积分数和晶化温度、晶化激活能的关系,并绘制了TTT曲线并计算非晶形成的临界冷却速率。结果表明,运用Kissinger法得到玻璃转变激活能E g为231.96 kJ·mol-1、晶化初始激活能E x为351.39kJ·mol-1、晶化峰的激活能E p为401.36 kJ·mol-1,Cu46Zr44Al5Nb5BMG具有良好的热稳定性,由TTT曲线计算非晶形成的临界冷却速率约为3.985 K·s-1。晶化类型主要为扩散控制的共晶型转变,随着晶化量的增大,阶段激活能呈减小的趋势。初始晶化阶段的晶化温度较高,主要是形核和微小晶粒的长大,需要克服较大的能量势垒,而随着温度的降低,晶粒的不断形成,晶化过程演变为主要以形核为主,所需要克服的能量势垒相应减小。在T x+100℃等温晶化退火,析出Cu10Zr7和AlCu2Zr共晶相,随着保温时间的延长,析出相的尺寸和体积分数逐渐增加。

Cu46Zr44Al5Nb5 bulk amorphous alloys were fabricated by suspend melting under an argon atmosphere using a water-cooled Cu mold. The heterothermal and isothermal crystallization behaviors were studied. The characteristics and local activation energy were calculated by Kissinger and FWO methods respectively, thus the relationship between crystalline volume fraction and crystallization temperature, crystallization activation energy were obtained. The results showed thatCu46Zr44Al5Nb5 BMG exhibited good thermal sta- bility. And the critical cooling rate for glass forming was about 3. 985 K.s^-1 from the TIT curve. The crystallization process was diffu- sion controlled eutectic transformation type. The glass transforming activation energy Eg, the crystallization starting activation energy Ex, the crystallization peak activation energy Ep were 231.96, 351.39 and 401.36 kJ·mol^-1, respectively. The local activation energy decreased gradually with the increase of the amount of crystallization. The crystallization temperature of the initial stage of crystalliza- tion should be higher so as to overcome the larger energy barrier for nucleation and small grains growth. As the temperature decreased, the grain continuously formed, and the crystallization evolved as a nucleation dominated process, the energy barrier for which was smal- ler. Isothermal crystallization annealed at T, ＋ 100 , Cul0Zr7 and AlCu2Zr eutectic phase were precipitated. The size and volume frac- tion of crystalline phase gradually increased as the holding time expansion.