高热稳定性Zr60Al10Co22Ag8非晶合金团簇玻璃相形成与分解

Formation and Decomposition of Clustered Glass Phase in Zr60Al10Co22Ag8 Amorphous Alloy with High Thermal Stability

摘要:

通过引入具有正混合焓和大原子尺寸差的Co-Ag原子对、降低Zr元素含量,设计出一种高热稳定性的Zr₆₀Al₁₀Co₂₂Ag₈非晶合金,采用真空熔融甩带法制备出合金非晶条带。将非晶条带在不同温度下进行退火,通过X射线衍射仪(XRD)、差示扫描量热仪(DSC)和透射电子显微镜(TEM)等手段研究了非晶条带的结构特征、晶化行为,探讨了Zr₆₀Al₁₀Co₂₂Ag₈非晶合金中团簇状非晶相的形成及其对合金热稳定性的作用。结果表明,Zr₆₀Al₁₀Co₂₂Ag₈熔纺条带形成了完全非晶相(Fully amorphous phase, am),加热时存在2个结晶放热峰。在高于T_x1温度下退火后形成了团簇状非晶相(Clustered glass phase,C-glass),即使退火时间高达24小时,Zr₆₀Al₁₀Co₂₂Ag₈合金仍表现为原子排布无序结构。其晶化行为为：[am] → [C-glass] → [C-glass’ + Al₂CoZr₆ + AgZr + Ag₂Al] → [Al₂CoZr₆ + AgZr + AlZr₃](其中,C-glass’为结晶残余团簇状非晶相)。具有正混合焓和大原子尺寸差的Co-Ag原子对的大量存在,导致组成元素长程重排困难,使得团簇状非晶相抵抗晶化的能力极高。这种形成团簇状非晶相、在较宽退火条件下具有抵抗晶化能力的非晶合金,为新型耐热非晶合金提供了新的设计思路。

Abstract:

An amorphous alloy Zr₆₀Al₁₀Co₂₂Ag₈ with high thermal stability was designed by introducing Co-Ag atom pair with positive mixing enthalpy and large atomic size difference and reducing Zr content. The as-spun amorphous alloy ribbons were prepared by vacuum single-roller melt-spinning method. The as-spun amorphous alloy ribbons were annealled at different temperatures. The structural characteristics and crystallization behaviors of the as-spun amorphous alloy ribbons were studied by X-ray diffraction (XRD), differential scanning calorimeter (DSC), and transmission electron microscope (TEM). The formation of clustered glass phase in Zr₆₀Al₁₀Co₂₂Ag₈ amorphous alloy and its effect on the thermal stability of the alloy were discussed. The results show that a fully amorphous phase (am) was formed in Zr₆₀Al₁₀Co₂₂Ag₈ as-spun alloy ribbons, and there were two exothermic peaks during heating. Clustered glass phase (C-glass) was formed after annealing at temperature just above T_x1. Even heating for up to 24 hours, the alloy ribbons still exhibited atomic disordered structure. The crystallization behavior was as follows: [am] → [C-glass] → [C-glass’ + Al₂CoZr₆ + AgZr + Ag₂Al] → [Al₂CoZr₆ + AgZr + AlZr₃] (where, C-glass" was the crystalline residual clustered glass phase). The existence of a large number of Co-Ag atom pairs with positive mixing enthalpy and large atomic size difference leaded to the difficulty of long range rearrangement of constituent elements, which induced the extremely high resistant to crystallization of clustered glass phase. This kind of amorphous alloys, which can form in clustered glass phase and resist crystallization at wide annealing condition, provide a new design method for new heat-resistant amorphous alloy.