Ag—10W机械合金化研究:亚稳固溶体的形成

Study on the Mechanical Alloying of Ag-10W Alloy: Formation of a Metastable Solid Solution

银和鸽在液态下也不互溶,混合热为很大的正值(△H=+156kJ/mol)。用高能球磨机对Ag～10W(wt.％)进行0～150h的机械合金化处理,经X-射线衍射、透射电镜、电子探针和DSC等分析表明:长时间(>70h)高能球磨后,合金中体心立方鸽的X-射线衍射峰及电子衍射谱消失,只存在面心立方银的衍射。合金中银的点阵参数随球磨时间的延长呈下降趋势。长时间球磨后,合金的晶粒尺寸为15nm左右。合金的储能在短时间球磨后很快提高,随球磨时间延长,储能下降,其变化趋势同合金中银的点阵参数及晶粒尺寸的变化趋势相似。说明钨原子进入了银的晶格,形成了Ag—W亚稳固溶体。

Abstract The mixing heat of silver and tungsten is large positive value (AH =+156kJ/mol) and s.ilver and tungsten are immiscible even at liquid state. AgWlO (wt·%) alloys were mechanically alloyed by high energy ball milling for 0～150 hours. The mechanically alloyed specimens were examined using X-ray diffraction, transmission electron microscopy, electron probe and DSC analysis. The results show that the X-ray diffraction peaks and electron diffraction pattern of bcc tungsten disappeared and only the diffraction peaks of fee silver are left after milling for 70hrs. The lattice parameter of silver decreases as the milling time increases. The grain size of the alloy is about I5nm after milling for long time. The stored energy of the alloy shows drastic increases after milling for a short time, then it decreases as the milling time increases. The trend of change in the stored energy is similar to that of changes in the lattice parameter and grain size. These results illustrated that the silver and tungsten have been mixed in the atomistic level and formed a metastable solid solution by the high-energy milling.