Theme Of Thesis: Formation And Properties' Study Of Aluminum Amorphous And Nano-crystal Alloy

This paper reports the results of investigation into the formation and thermal stability of the amorphous Al-Ni-Zi-Y and Al-Ni-Zi-Cu-Y alloy ribbons Prepared by melt spinning method under vacuum and atmosphere conditions. As-melt-spun amorphous alloy ribbons and quench amorphous alloy ribbons' tissue and microstructures and GFA were investigated by x-ray diffraction and scanning electron microscopy and differential scanning calorimetry (DSC). It is found that addition of Yttrium and Copper element into Al85Ni8Zr3Cu2Y2 amorphous alloy increases the GFA and thermal stability of Al85Ni10Zr5 alloy apparently. At the same time It could find no matter in vacuum or atmosphere conditions similar X-ray diffraction patterns were obtained from both alloy ribbons. All traces show the broad amorphous peak, indicating the existence of a single amorphous phase or primary amorphous phase structure. The different is that there are sharp peaks superimposed the broad amorphous peak and the peak of crystalline phase is demarcated as the face-centered-cubic Al (a-Al)). Compare with the processing conditions, composition and cooling rate play an important role in formation of Al-Ni-Zi-Cu-Y amorphous alloys.It also can find that the addition of Y promote the formation of a-Al and compound phase, which reduce the GFA of Al-Ni-Zr alloy. On the contrary increase the crystal temperature of Al-Ni-Zr alloy, on the basic of Al-Ni-Zi-Y alloy, the addition of suitable Cu element can reduce the formation of a-Al and compound phase effectively. At the same time Increase the formation ability and thermal stability of Al-Ni-Zi-Y alloy. However with the increase of Cu element, the GFA and thermal stability reduce apparently. There are no Tg which is taken as the onset temperature of this endothermic signal can be observed since crystallization takes place first and there are pre-exist a-Al nucleus distract in amorphous. The effect of Cu in refining the size of the nano-crystals was attributed to enhance nucleation increasing the number density of the nano-crystals.It also can found Al85Ni8Zr3Cu2Y2 alloy and Al85Ni10Zr5 alloy can form nano-crystal a-Al embedded in amorphous structure by the means of quench at certain condition or heat treatment at initial crystal temperature for 30min.