压力对La-Al-(Cu,Ni)金属玻璃结构驰豫的影响

Pressure Effects on Structural Relaxation of La-Al-(Cu, Ni) Bulk Metallic Glass

摘要:

采用铜模吸铸法制备出La62.0Al15.7(Cu0.5Ni0.5)22.3大块金属玻璃，经高压处理后，用X射线衍射仪(XRD)和示差扫描量热计(DSC)对非晶的结构驰豫和晶化过程进行了研究。结果表明，非晶玻璃转变温度和第一晶化温度随着压力的增加，其先增加后减小，极大值出现在4.0 GPa的压力。这种现象归因于经过高压处理后玻璃转变温度区焓的变化，而焓的变化由基体缺陷激活体积引起自由体积变化所导致。此外，高压处理还影响玻璃的结晶过程。

Abstract:

In this study, La62.0Al15.7(Cu0.5Ni0.5)22.3 bulk metallic glasses (BMGs) were prepared by copper mold casting method, and the effects of the pressure treatment up to 5.0 GPa at room temperature on structural relaxation were investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The results showed that structural relaxation occurred with changes of the glass transition temperature (Tg) and the onset of primary crystallization (Tx1). Both increased with increasing of applied pressure up to 4.0 GPa beyond which they decreased. The enthalpy changed at the glass transition temperature regime showed that the reduction of the free volume caused by the HP treatment can be interpreted by the activation volumes of the flow defects. Furthermore, the HP treatment also influenced the crystallization sequence of the BMG.