Study Of Diffusion Behavior Between Al₇₂Co₂₀Ni₈Decagonal Quasicrystal And Cu

Traditional method of powder metallurgy is adopted to composite Al₇₂Co₂₀Ni₈quasicrystaland copper together．The experiment observes varying degrees of reaction by adjusting the heattreatment conditions in the application of X-ray diffraction（XRD）， scanning electronmicroscopy（SEM），transmission electron microscopy（TEM） and other techniques．This thesis consists of three main：（1） morphology of Al₇₂Co₂₀Ni₈decagonal quasicrystal；（2） interface research of Al₇₂Co₂₀Ni₈decagonal quasicrystal and copper at the temperature of550℃；（3） the diffusion behavior between Al₇₂Co₂₀Ni₈decagonal and copper at the temperature of700℃；In this paper，casting Al₇₂Co₂₀Ni₈quasicrystalline material prepared successfully by methodof conventional casting in accordance with the atomic percentage Al₇₂Co₂₀Ni₈in a vacuuminduction furnace．Ten-prism morphology of Al₇₂Co₂₀Ni₈decagonal quasicrystal is observed byscanning electron microscopy （SEM）. Spectrum analysis （DEAX） proves the composition of theingot is Al₇₂Co₂₀Ni₈．Two-dimensional ten fold rotational symmetry structure is verified usingtransmission electron microscopy high-resolution（HRTEM） and selected area electrondiffraction（SAED）．Grind Al-Ni-Co quasicrystal into powders with the particle size of60μm using ball milling，mix the Quasicrystals and Cu homogeneously as weight ratio of1:19，then press into circularComposite materials which then sintered at550℃with the holding time of30min,45min,60minrespectively．Observe the interface of Al-Ni-Co quasicrystal and Cu matrix by scanning electronmicroscopy（SEM），and analyze t interface composition changes using attached energy dispersivespectroscopy（EDAX）．The experimental results show there are only some Co Atoms that diffusefrom Al-Ni-Co quasicrystal to the copper matrix with Al atoms still bound in the quasicrystal，but not significant element exchange around the interface at550℃．In the next stage,set up sintering temperature at700℃with the respective hold time20min，40min，80min，120min aiming to Al atom diffusion．Experimental data indicatesAl₇₂Co₂₀Ni₈quasicrystal particles are firstly decomposed into lamellaes of Al（Co,Ni）_xcrystals,which occur aggregation and coarsening as the increasing holding time．Al atoms diffuseinto the Cu matrix to form supersaturated solid solution，and there are distributed nano-scaleprecipitates in the matrix after cooling．The paper attributes this phenomenon to activity of Alatoms in Al₇₂Co₂₀Ni₈quasicrystal at700℃．Al₇₂Co₂₀Ni₈quasi-periodic structure can`t maintainowing to the loss of Al atoms,then strong solubility and diffusion occur on the interface．...