Study On Microstructure And Property Of Laser Additive Manufacturing Zr-Al-Ni-Cu Amorphous Materials

Amorphous alloys have attracted great attention owing to their exceptionalphysical, chemical and mechanical properties, becoming a great potential ofnew functional material. However, the critical dimension of the amorphouscoating is limited by the conventional coating preparation methods, whichrestricts its widespread application.This study based on the formation mechanism of amorphous alloys, inview of the urgent desire of large dimension amorphous materials preparation.We used the laser additive manufacturing which has a quickly heating andcooling rate, successfully prepared various thickness of Zr65Al7.5Ni10Cu17.5amorphous materials. And a systematic study on the laser temperature fielddistribution, technique of laser additive manufacturing, microstructure and theproperties of the Zr65Al7.5Ni10Cu17.5amorphous material was conducted.Simulation analysis of laser processing temperature field was taken usingANSYS software, mechanisms of interaction and heat transfer in the laseradditive manufacturing amorphous material process were analyzed. Obtainedthe rapid heating and cooling rate of laser source and steep temperature gradientcharacteristic. Analyses of the amorphous material surface topography, stireffect of the melt pool and porosity formation were made. And the melt poolshape of single layer single track was speculated. Which built the theoreticalbasis of the experiment.During the laser additive manufacturing Zr65Al7.5Ni10Cu17.5amorphousmaterials through high power continuous CO2laser, discussion and analysisabout the influence of laser parameters on the morphology and microstructure ofthe amorphous material were made. One-layer1mm thick, two-layers1.2mm thick, three-layers1.4mm thick and five-layers1.7mm thick Zr65Al7.5Ni10Cu17.5amorphous materials were prepared using the optimized parameters P=3300W,v=180mm/min,. Crystals and amorphous all existed in the materials,crystallization occurred mainly close to the substrate due to the dilution. Theamorphization increased along with the increase of thickness.By comparatively analyzed the phase and component of the different areasin amorphous material, the XRD results showed amorphous broad peaks at2=38°. The volume fraction of amorphous phase in the5th layer,3rd layerand1st layer are approximately77%,64%and49%. The chemical compositiondistributed uniform in the middle and upper part, close to the ideal componentZr65Al7.5Ni10Cu17.5. Close to the substrate, there is a520dilution zone. Theelement introduced by the dilution disturbed the chemical composition thenrestricted the formation of amorphous.Thermal stability test, hardness test, electrochemical corrosion experimentwere taken to the substrate and various thickness laser additive manufacturedZr65Al7.5Ni10Cu17.5amorphous materials, analyzing the properties comparatively.As the heating rate increase from10℃/min to30℃/min, the glass transitiontemperature Tgraise from639℃to653℃, initial crystallization temperature Txdecrease from721℃to692℃, the supercooled liquid region T=Tx-Tgdecrease from82℃to39℃, and the thermal stability of the amorphous materialdecrease along with the heating rate increase.The different thickness amorphous materials show a similar hardnessdistribution characteristic, that is, the hardness first increased and thendecreased from the surface to the bottom. The five layers sample exhibits themaximum hardness value1033HV.Passivation exist in different thickness amorphous materials, and they havesimilar corrosion potentials, which are higher than the substrate. Significantdifferences in corrosion current: substrate7.97410-5A/cm2，one layer5.94410-5A/cm2， three layers2.25210-6A/cm2， five layers8.56510-7A/cm2。The impedance of amorphous materials are larger than the substrate, and with increasing the thickness, the impedance improves. Thecorrosion process is divided into early, middle and late three stages, analyzedwith the equivalent circuit diagram. Passivation occurs in the early stage,generating the isolation layer. The passive film are breakdown and microporousformed in the middle stage. In the late stage, the microporous etched to macrohiatus, corrosive liquid contact the substrate.