高热稳定性Zr_(60)Al_(10)Co_(22)Ag_(8)非晶合金团簇状非晶相形成与分解

Formation and Decomposition of Clustered Glass Phase in Zr_(60)Al_(10)Co_(22)Ag_(8) Amorphous Alloy with High Thermal Stability

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Zr_(60)Al_(10)Co_(22)Ag_(8)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Zr_(60)Al_(10)Co_(22)Ag_(8)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,Zr_(60)Al_(10)Co_(22)Ag_(8)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。在高于第1次放热开始温度(Tx1)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 h,Zr_(60)Al_(10)Co_(22)Ag_(8)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’+Al_(2)CoZr_(6)+AgZr+Ag_(2)Al]→[Al_(2)CoZr_(6)+AgZr+AlZr_(3)](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。

An amorphous alloy Zr_(60)Al_(10)Co_(22)Ag_(8) 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 annealed at different temperatures.The structural characteristics and crystallization behavior of the as-spun amorphous alloy ribbons were studied by X-ray diffractometer(XRD),differential scanning calorimeter(DSC),and transmission electron microscope(TEM).The formation of clustered glass phase in Zr_(60)Al_(10)Co_(22)Ag_(8) amorphous alloy and its effect on the thermal stability of the alloy were discussed.The results show that a fully amorphous phase(am) is formed in Zr_(60)Al_(10)Co_(22)Ag_(8) as-spun alloy ribbons,and there are two exothermic peaks during heating.Clustered glass phase(C-glass) is formed after annealing at the temperature just above Tx1.Even being heated for up to 24 h,the alloy ribbons still exhibit atomic disordered structure.The crystallization behavior is as follows:[am]→[C-glass]→[C-glass' +Al_(2)CoZr_(6)+AgZr+Ag_(2)Al]→[Al_(2)CoZr_(6)+AgZr+AlZr_(3)](where C-glass' is 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 leads to the difficulty of long range rearrangement of constituent elements,which induces the extremely high resistance to crystallization of clustered glass phase.This kind of amorphous alloys,which can produce clustered glass phase and resist crystallization under wide annealing conditions,provide a new design method for new heat-resistant amorphous alloy.