Cutting Property Of Vit1Bulk Metallic Glasses

With the excellent mechanical, physical and chemical properties, such as highstrength, high hardness, high fracture toughness, low density, good corrosion resistanceand resistance to radiation of high energy particles, Zr-based bulk metallic glasses (BMGs)are envisaged to have wide range functional and structural a_pplications. For its highhardness and brittleness at room temperature, machining of Zr-based BMGs is confrontedwith some difficulties. Here the cutting property and its influencing factors wereinvestigated systematically based on the materials of Zr41.2Ti13.8Cu12.5Ni10.0Be22.5(Vit1)BMGs.The cutting temperature and its influence to amorphous structure of the finishedsurface were studied by combination of experiment and simulant calculation under thecondition of three different kinds of cutting speed(v), deepth of cut(a_p) and feed rate perrevolution(f). The temperature at the tool-workpiece interface were535.5℃,470.1℃and437.3℃respectively for WC-Co based cemented carbide, PCBN and PCD tools under thecondition of v=1.06m/s, a_p=0.3mm, f=0.12mm/r. The quality of the finished surface cutwith the cemented carbide cutting tool can achieve the fine surface roughness. Theinfluences of cutting heat to the structue of the workpiece and chip were analysed and theresults showed that any crystallization occurred on the surface of the finished surfaceand on the cross section of the chip under the condition of the experiment. The Vit1BMGspossess good cutting processability.Though Vit1BMGs show brittleness at room temperature, in the course of lathecutting, the brittleness was weakened with the temperature raise of the finished surfaceand chips caused by the cutting heat. These would bring notable influences to the cuttingproperty and the formation and deformation of the chips. Cutting speed is an importantfactor to the cutting heat. The continuous chips were consisted of overla_pped shearlamellas under the condition of v=1.06,0.50,0.25m/s, a_p=0.3mm, f=0.12mm/r.The temperature raise of the lamellar chip unit was calculated with the principalcutting force and the results were823℃,625℃and531℃for v=1.06m/s,0.50m/s,0.25m/s, a_p=0.3mm, f=0.12mm/r. The formation and deformation of the cutting chip were influenced directly by the temperature of chip. The chip formed under suitabletemperature is propitious to improve the surface roughness.The influences of cutting parameters to cutting force and surface roughness werestudied by orthogonal experiments with three factors and three levels under differenttechnical parameters (v, a_p, f) with cemented carbide cutting tool. The results showed thatthe deepth of cut did more influences to the cutting force than the feed rate per revolutionand that of the cutting speed was the smallest one among the three parameters.Considering the effection of cutting parameters to surface roughness of the finishedsurface, the feed rate per revolution was stronger than cutting speed and deepth of cut didthe weakest affection.Investigation of fraction and wear of the cutting tool showed that the wear of cuttingtool was affected by cutting speed seriously when deepth of cut and feed rate perrevolution were set as a fixed value. High cutting temperature brought cohesion betweencutting tool and chip or finished surface. Thermal softing of the cutting tool induceddeformation and subsidence on blade of cutting tool and increased wear of rake face.When the cutting parameters were set as v=1.06m/s,a_p=0.2mm and f=0.08mm/r, wear ofthe cutting tool can be reduced to low degree and good surface roughness would beobtained.The drlling temperature of Vit1BMGs was measured with thermal couple and thetemperatures reached at164.5℃and371.5℃when drilling speed is200and2000r/min.The surface roughness of the drilled hole and wear of the drilling tool were affectedmarkedly by drilling heat. When the feed rate was set as0.04-0.06mm/r, the quality of thedrilled hole increased with decrease of drill speed. When drill speed was2000r/min, thedrill heat can lead to coarse hole surface and thermal softening, deformation of thematerial on the drilled hole. Some burrs and melted chips existed on the entry of hole.When drill speed was lower than800r/min, the quality of the hole improved notablely.