Experimental Study On The Influence Of Electrode Material On The Processing Performance Of Zr-based Metallic Glasses By EDM

Metallic glasses are metal alloys with no long-range atomic order,These materials can exhibit unique mechanical properties,such as high strength,high hardness,excellent fracture toughness,and strong corrosion resistance,etc.They have broad application prospects in the fields of aerospace and military,sports equipment preparation,power transmission,medical and health care.However,the further widespread application of metallic glasses is inseparable from the secondary precision forming processing.Conventional machining of metallic glasses by general cutting,there are problems such as serious tool wear and low processing efficiency.The EDM electrode tool and the workpiece do not contact,but rely on the continuous generation of pulsating spark discharge between the tool and the workpiece,which can remove the workpiece material.EDM technology has obvious advantages over the conventional cutting processing in the processing of small holes,cavities,shaped holes and certain thin-walled parts,etc.Therefore,this thesis investigates the EDM performance of Zr-based metallic glasses as a research target to provide some reference for further understanding of the EDM mechanism of this material.A main effects analysis,analysis of variance(ANOVA),and response surface methodology(RSM)were performed on the material removal rate(MRR)and surface roughness(SR)of Zr-based metallic glasses(shallow cylindrical surface)by EDM parameters(current,cycle,efficiency,and gap voltage)using two different electrodes(purple copper and tungsten copper).The results show that when Zr-based metal glass is processed using purple copper electrodes,the order of influence of electrical processing parameters on MRR is:efficiency > current > cycle > gap voltage.The most optimal combination of parameters is:current 10 A,cycle 80?s,efficiency 40% and gap voltage 20 V.While for tungsten copper electrodes,the order of influence of electrical processing parameters on the MRR is: current >cycle> efficiency > gap voltage.The most optimal combination of parameters is: current 10 A,cycle 50?s,efficiency 30% and gap voltage 80 V.For the SR,the order of influence of electrical parameters on the processing of Zr-based metallic glass using both electrodes are:current > cycle > efficiency > gap voltage.When machining Zr-based metal glasses with copper electrodes,the best combination of electrical parameters to obtain minimum SR is:current 4A,cycle 50?s,efficiency 10%,gap voltage 80 V.Further,with the help of single-factor experiments,the effects of different electrode materials and four EDM parameters on the MRR and SR of Zr-based metallic glass.The machined surface morphology of the workpiece and the used surface morphology of the electrode were comparatively analyzed.When the Zr-based metallic glass was processed with the purple copper electrode,the MRR and SR of the processed surface were larger than of the tungsten copper electrode.No micro-cracks and pores were found on the surface of the Zr-based metallic glass after the two electrodes were processed.The morphological characteristics of the end surfaces of the two electrodes after using were mainly different in terms of micro-cracks,carbon black films and the number of pores.In order to further analyze the EDM performance of Zr-based metallic glass,by using orthogonal and single-factor experiments,the effects of different electrode and electrical processing parameters on the electrode loss and through-hole diameter during EDM of Zr-based metallic glass was investigated It was found that the electrode loss of tungsten copper electrode was twice or more than that of purple copper electrode,In the orthogonal experiment,the maximum electrode loss of tungsten-copper electrode reached 0.019 g,while the electrode loss of purple-copper electrode was only 0.011 g,and it showed an unstable discharge state.After processing Zr-based metallic glasses with tungsten copper electrode,its through-hole diameter was overall larger than that of purple copper electrode.Meanwhile,based on the results of single-factor test,the microscopic morphology of the end face and side face of the two electrodes after using were analyzed.Besides,the morphology of the side wall of the workpiece through-hole after machining of the two electrodes were analyzed.The results showed that the workpiece side walls of the purple copper electrode were covered with carbon black film,while the side walls of the tungsten copper electrode were covered with obvious round molten drops.The micro-sphere diameter is around 8?m,and when the current increases to 8A,the micro-sphere diameter is around 20?m.The number of micro-cracks on the electrode end face and electrode side are more and longer after machining with tungsten copper electrode.While the micro-cracks on the electrode side after machining with both electrodes were finer than those on the electrode end face.Compared with tungsten copper electrode,the quality of electrode end face and electrode side after processing with purple copper electrode is better.