退火温度对Mg_(61)Cu_(28)Gd_(11)块体非晶结构与性能的影响

Effect of annealing temperature on structure and properties of Mg_(61)Cu_(28)Gd_(11) bulk metallic glasses

对Mg61Cu28Gd11块体非晶在其玻璃转变温度以下温度(325、350、375和400 K)等温退火1 h,用X射线衍射仪(XRD)、差热扫描量热仪(DSC)、纳米压痕仪、扫描电子显微镜(SEM)、显微维氏硬度计等分析研究了低温退火对其热稳定性、微区力学性能及变形的影响,并分析了塑性变形机理。结果表明,低温退火后非晶原子的短程有序性增加,非晶结构的稳定性变差,并在400K发生部分晶化。同时,在325～375 K范围内,显微硬度和弹性模量E随退火温度的升高而增大,塑性变形量Dn和最大压入深度Dmax减小;400 K退火后,由于少量析出的晶体相与压头下新产生的自由体积相互作用,合金抵抗变形能力减弱,显微硬度和弹性模量E降低,Dn和Dmax提高。

Mg61Cu28Gd11 bulk metallic glasses（BMGs） were isothermally annealed for 1 h at the temperatures（325,350,375 and 400 K） below its glass transition temperature.Effect of low annealing temperature on thermal stability,mechanical properties and deformation of the amorphous alloys were studied by means of X-ray diffraction（XRD）,differential scanning calorimeter（DSC）,nanoindentation instrument,scanning electron microscope（SEM） and micro-Vickers hardness tester,and the plastic deformation mechanism was also analyzed.The results indicate that the short range orderings of the atoms in amorphous alloy increase with the increasing of annealing temperature,while the structure stability becomes weaker,and the BMG partially crystallizes after annealing at 400 K.In the meanwhile,microhardness and elastic modulus（E） values increase and plastic deformation value（Dn） and the maximum indenting depth（Dmax） for nanoindentation tests decrease as the temperature increases from 325 K to 375 K.The interaction of the crystal phases precipitated after annealing at 400 K and new free volume generated under the indent tip weakens the deformation resistivity and causes the microhardness and E values to reduce,but the Dn and Dmax values to increase.