材料期刊网

为深入理解非晶合金的晶化行为,有效控制合金的微观结构和性能,本文利用铜模铸造法制备了Gd36La20Al24Co20块体非晶合金,通过X射线衍射和差示扫描量热法对该非晶合金的热稳定性和晶化行为进行了研究.结果表明：Gd36La20Al24Co20块体非晶合金的晶化激活能为282.5 kJ/mol;与轻稀土基非晶合金相比,具有较高的热稳定性.利用J-M-A方程对其等温晶化动力学进行了分析,该合金平均Avrami指数为2.78～3.3.区域Avrami指数n（x）分析表明,晶化初期n（x）趋于2,表明晶化开始是由一维扩散控制的;晶化中期阶段,n（x）由2.5变化到3.5,在此过程中,当2.5〈n〈3时,新相长大,形核率增加,当3〈n〈3.5时,新相继续长大,形核率降低;晶化末期,n（x）趋于4,表明晶化过程是形核速率恒定和长大速率恒定的过程.

To understand the crystallization behaviors of amorphous alloys and to control their microstructures and properties,Gd 36 La20 Al24 Co20 BMGs were prepared by copper-mold casting.The crystallization behavior and thermal stability of Gd36 La20 Al24 Co20 were investigated by X-ray diffraction and differential scanning caloricity（DSC）.The results show that the activation energy of crystallization of Gd 36 La20 Al24 Co20 BMGs is 282.5 kJ/mol,and it has a higher thermal stability compared with light rare earth based metallic glasses.The isothermal kinetics was modeled by the Johnson-Mehl-Avrami equation.The Avrami exponents were calculated to be in the range of 2.78 to 3.3.The average value of local Avrami exponents shows that at the initial stage the value of n is about 2,indicating that the crystallization process is controlled by one-dimensional diffusion process.In the main crystallization stage,the value of n changes from 2.5 to 3.5.In this stage,the crystallites grow up at increasing nucleation rate with 2.5n3;the crystallites continue to grow up at decreasing nucleation rate with 3n3.5.In the final stage of crystallization,the value of n is close to 4,implying that the phase transformation occurs in a three-dimensional mode with a constant nucleation rate and a constant growth rate.