Machining Chips Research Articles

Characterization of Chip Morphology for Aluminum Metal Matrix Composites in End Milling Machining

End milling using a solid mill cutter is widely used in aerospace, automotive, biomedical, and chemical industries. However, a comprehensive characterization of chip morphology and micro structural and mechanical behavior of machined chips is lacking in the literature. A series of end milling experiments were conducted for studying the chip morphology of Aluminum metal matrix composite. A new multi-view approach to fully characterize metallurgical aspects of chip& chip morphology including top surface and free surface is taken up in this research paper. Each view of the 3-dimensional (3D) chip has been studied for different characteristics. The variation of chip dimensions with cutting parameters was also determined.

Effect of ball milling on the physical and mechanical properties of the nanostructured Co–Cr–Mo powders

In the present study, Co-based machining chips (P1) and Co-based atomized alloy (P2) has been processed through planetary ball mill in order to obtain nanostructured materials and also to comprise some their physical and mechanical properties. The processed powders were investigated by X-ray diffraction technique in order to determine several microstructure parameters including phase fractions, the crystallite size and dislocation density. In addition, hardness and morphological changes of the powders were investigated by scanning electron microscopy and microhardness measurements. The results revealed that with increasing milling time, the FCC phase peaks gradually disappeared indicating the FCC to HCP phase transformation. The P1 powder has a lower value of the crystallite size and higher degree of dislocation density and microhardness than that of the P2 powder. The morphological and particle size investigation showed the role of initial HCP phase and chemical composition on the final processed powders. In addition results showed that in the first step of milling the crystallite size for two powders reach to a nanometer size and after 12h of milling the crystallite size decreases to approximately 27 and 33nm for P1 and P2 powders, respectively.

DEM Simulation of Ceramic Tool Abrasion in Machining Superalloy

The discrete element method (DEM) model which describes the friction and abrasion behavior of the interface between Sialon ceramic tool and superalloy chip in machining were established, effects of cutting speed and depth of cut on tool abrasion were numerically investigated. The abrasion behaviors of the Sialon ceramic tool mainly appear in terms of abrasive wear, fatigue wear, adhesion wear and diffusion wear. The DEM simulation results show that, within a certain range, the higher cutting speed effectively results in the slighter wear of Sialon ceramic tools, meanwhile the deeper depth of cut leads to more serious tool wear. It is further validated that discrete element method is feasible to simulate the tool wear behavior.

Achieving Superior Strength and Ductility in Ti-6Al-4V Recycled from Machining Chips by Equal Channel Angular Pressing

Ti-6Al-4V machining chips were recycled using equal channel angular pressing. The as-recycled material was fully dense and well bonded, but contained chip boundaries decorated by entrapped surface oxide, giving rise to brittleness in tensile loading. Annealing at high temperatures was effective in removing the oxide. The times required for completely dissolving the oxide layers were calculated using models based on oxygen diffusion in α- and β-Ti, respectively. It is shown that the oxide dissolution is rapid, taking from several minutes to less than one second at temperatures between 973 K and 1323 K (700 °C and 1050 °C) for thicknesses of up to 1 μm. In addition, bands of grains finer than those in the matrix occurred in the vicinity of the prior chip boundaries, caused by the enhanced level of oxygen diffusing away from the dissolving oxide which hindered local grain growth. It would take hours of annealing to homogenize the grain size and composition. The as-recycled material was subjected to conventional mill-annealing, leading to a finer microstructure with superior yield strength (~1150 MPa) and equivalent tensile ductility (~25 pct), compared to a commercial mill-annealed Ti-6Al-4V.

New Design of Aluminium Based Composites through Combined Method of Powder Metallurgy and Thixoforming

The present study deals with a new design of aluminium alloy based composites reinforced with SiC particles and Si/Al2O3 powders through combined methods of powder metallurgy and thixoforming. Moreover, recycled machining chips are used as raw material, specifically AA7075 chips generated in the aeronautical industry. The proposed method is based on forming at high temperatures a compacted mixture of metal chips and reinforcing particles, with the metal in thixotropic semi-solid condition. Composites containing different SiC weight fractions (10, 20 and 30%) were produced and had their microstructure analyzed. Mechanical properties were evaluated by means of micro-indentation tests. General results show the feasibility of producing composites by the proposed route. Products with good mechanical properties could be obtained. The process, even still not completely optimized as some improvement still must be achieved, can bring a new possibility for the production of a noble material from recycled wastes, particularly important in the high energy spending Al industries.

Investigation of the Effect of Rake Angle on Large Strain Extrusion Machining

This paper describes how tool rake angle affect the chip formation during large strain extrusion machining. The simulation studies were corroborated by experiments where pure copper workpieces were extrusion machined using different rake angles and the machined chips were characterized for microstructure and mechanical properties. Both simulation and experimental results showed that rake angle had a significant effect on deformation field parameters and cutting force. Associated to the nanostructured materials formation, grain refinement in primary deformation zone is due to the larger strain imposed. And the increase in hardness in machined chips was a consequence of the reduced grain sizes.

Production of Wire From AA7277 Aluminum Chips via Friction-Stir Extrusion (FSE)

In this research, fully consolidated wires from aluminum alloy AA7277 machining chips were produced by the friction-stir extrusion (FSE) process. The components used in the friction-stir extrusion process consist of a stationary cartridge and a rotating plunger with a scroll-faced head. The rotating plunger was rotated at three different speeds. Optical microscopy was used to probe the microstructures formed in the wires. The hardness profile of each sample is characterized using a Vickers microhardness tester. In this work, surface quality is sufficient by using a rotation speed of 160 rpm. Cold crack and hot crack defects were shown on wires fabricated using either too low or too high plunger rotation speeds. The microstructure of extruded wire is composed of fully equiaxed, recrystallized fine grains in the center of samples. The microhardness tests show an uneven distribution, and the hardness of the center was lower than that of the parent metal. The tensile tests revealed that the mechanical properties of the extruded wires were comparable with parent material.

Development of Multi-Wire Electric Discharge Machining for SiC Wafer Processing

In order to slice the larger size ingot toward 6 inch of silicon carbide (SiC), we are developing Multi-wire Electric Discharge Machining (EDM). To prevent wire break during slicing, we have developed the electric discharge pulse control system. So far, with 10 multi-wires, we have succeeded in slicing of 4 inch SiC balk single crystal without wire break. High quality slicing surface (e.g. small value of around 10 μm of SORI for 3 inchi wafer) was also achieved. By polishing methode, EDM-sliced wafer was estimated to have the uniform thickness of damaged layer over the entire surface. We confirmed that the wafer sliced by EDM can be processed in the later process, by grinding the 3 inch wafer. And it was confirmed that 6 inch ingot can be sliced with 10 multi-wire EDM, by slicing the boule of SiC poly crystal. For the larger diameter ingot than 4 inch, Multi-wire EDM will be practically used by the effective removal of machining chips from the machining clearance between the wire and work.

Numerical contribution to the comprehension of saw-toothed Ti6Al4V chip formation in orthogonal cutting

Abstract The physics of formation of a saw-toothed (or segmented) Ti6Al4V chip in machining is still an ongoing issue in the literature as well as its modelling and numerical simulation. After a review of the theories explaining the formation of such a chip, three finite element models are presented with a desire to take into account the physical phenomena. The results of the simulations are compared with the different theories reported in the literature. This confrontation allows us to keep the most relevant model which contributes to the understanding of the phenomena. It shows that combining the adiabatic shear band and the crack propagation leads to a chip morphology and formation mechanism close to the experimental one. The study also allows to estimate the teeth formation frequency of the numerical chip.

Review of Aluminum Chip Machining Using Direct Recycling Process

This paper reviews the chain of aluminum Direct Recycling process. Direct Recycling is one of intelligent process to recycle the aluminum waste. The current method for recycle waste aluminum, was affect on the environmental issues. This paper focus on the aluminum waste from machining process, also called chips produced from turning and milling process. From chip collected, next compaction process are compressed to the certain amount pressure for consolidating the materials. Lastly to produce a new material, the process is extrusion process. The most important issue to get a quality of a product is, how to control the pressure during both of process. During this process also available in hot and cold condition. From review, it was that cold compaction process more popular implemented compared to hot compaction. Then almost researchers applied hot extrusion it is because to cover sintering process.

Analytical modeling of adiabatic shear band spacing for serrated chip in high-speed machining

Theoretical prediction of adiabatic shear band spacing is beneficial to understand the mechanism of the serrated chip formation. The momentum equation, energy equation and compatibility equation in orthogonal cutting are established in this paper. Using perturbation analysis by regarding cutting speed and uncut chip thickness as basic disturbance, an analytical solution of adiabatic shear band spacing is developed. Adiabatic shear band spacing of serrated chip is related to the wave number of the perturbation when the growth rate reaches to maximum. It is found that adiabatic shear band spacing decreases with the increase of cutting speed but increases with uncut chip thickness. The experiment of orthogonal cutting Ti6Al4V under different cutting speeds (50 m/min-1800 m/min) and uncut chip thicknesses (0.02 mm-0.16 mm) verifies the validity of the theoretical prediction.

黄銅切削屑の再利用技術(<メカライフ特集>転のものづくり)

黄銅切削屑の再利用技術(<メカライフ特集>転のものづくり)

Recycling of Aluminum Chips by Hot Extrusion with Subsequent Cold Extrusion

In this paper, the direct conversion of AA6060 aluminum alloy machining chips into finished products by hot extrusion with subsequent cold extrusion is investigated. For hot extrusion, two different types of extrusion dies, a conventional flat-face die and an experimental die, are used. The experimental die combines the process of equal channel angular pressing with the process of hot extrusion in a single die, which increases the strain and pressure affecting the chips during extrusion, both critical factors for achieving sound chip bonding. Subsequently, the chip-based extrudates are machined to fabricate chip-based preforms for the cold extrusion experiments. In order to investigate different processing routes, forward rod extrusion and backward can extrusion trials were conducted. In all steps, cast material was processed similar to the chips as a reference. The results showed that the quality of the chip-based finished parts strongly depends on the bonding quality between the individual chips, determined during the hot extrusion process.

Propiedades mecánicas de la aleación AZ31 procesada por una ruta eco-sostenible

Recently it has been proved that molding of defect-free components of various commercial alloys of magnesium can be carried out succesfully when small amounts of CaO are added to the melt, making unnecessary the use of SF 6 coverage. In the case of AZ alloys, this process also remarkably improves their mechanical properties not only by the greater cleaning of alloys but also by the formation of CaAl 2 phase. This work, part of the Green project Metallurgy ( http://www.green-metallurgy.eu ) funded by the European Union (LIFE+2009), studies the influence of different CaO additions on the microstructure and mechanical properties of AZ31 Eco-Mg alloy. The alloy was processed by a conventional route involving extrusion of as-cast rods as well as by a powder metallurgy route (PM) using chips as starting material. The objective was to analyze the viability of recycling machining chips to manufacture components for the automobile industry and transportation in general, because of its low cost and environmental impact. It has been demostrated that alloys processed from chips exhibit the highest tensile stress values, close to 320 MPa.

Multicomponent materials from machining chips compacted by equal-channel angular pressing

Al and Mg machining chip blends were compacted by equal-channel angular pressing with back pressure. By varying the weight fraction of the constituent materials, temperature and processing route, as well as employing subsequent heat treatment, the microstructure and the mechanical properties of the compact were varied. The width of the interdiffusion zone and the formation of intermetallic phases near the interfaces between the two metals were studied by energy-dispersive X-ray spectroscopy and nanoindentation. It was shown that substantial improvement of mechanical properties, such as an increase of strength, strain-hardening capability and ductility, can be obtained. This is achieved by changing the processing parameters of equal-channel angular pressing and the annealing temperature, as well as by optimising the weight fraction of the constituent metals.

Microstructural evolution and microhardness change of Al–7wt%Si–0.3wt%Mg alloy granules/powder particles during high energy ball milling

Al–7wt%Si–0.3wt%Mg alloy granules produced by mechanical crushing of machining chips were subjected to high energy ball milling. It was found that ball milling significantly reduced the sizes of eutectic Si particles from micrometer level to submicrometer level, changed their morphology from being faceted into being rounded, and caused formation of stacking faults in them. Ball milling also resulted in a drastic change of the Al(Si,Mg) matrix by increasing its Si content from 0.16 to 1.81at%, and reducing its average grain size to 45nm. These microstructural changes of the powder particles lead to a dramatic increase of the microhardness of the powder particles to 187HV, which is more than twice that of the original granules. Analysis of the contributions of various strengthening mechanisms shows that the major contribution to the microhardness increase comes from grain refinement.

Study of Nano-Mechanical Characterization of Minimum Chip Formation Using Atomic Force Microscopy

Derived the approximate relationship between minimum cutting thickness and tip radius, ratio of vertical load and shear force, friction coefficient between tip and sample. Wire was being processed by changing the load size. The critical load of chip formation and machining thickness were found from atomic force scan picture. Contrast tests were done by transforming the specimen. The experimental results are basically consistent with the derived values.

Microstructure evolution and mechanical properties of Al–Zn–Mg–Cu alloy reprocessed by spray-forming and heat treated at peak aged condition

Abstract Machining chips of the alloy AA7050 were reprocessed by spray forming followed by hot-extrusion and heat treatment. The spray-formed deposit presented a microstructure with hardening η′ precipitates within the matrix and equilibrium η precipitates at the grain boundaries, refined grains and low segregation of the main elements Zn, Cu and Mg. The final microstructure at peak aged condition is mainly composed by Guinier–Preston (GP) zones, η′ metastable, η equilibrium , Al3Zr dispersoids and the coarse Al7Cu2Fe intermetallic. A well-defined precipitation free zone along grain boundaries was not observed. Good mechanical properties were achieved.

Investigations of yield stress, fracture toughness, and energy distribution in high speed orthogonal cutting

This paper presents a novel prediction method of the yield stress and fracture toughness for ductile metal materials through the metal cutting process based on Williams' Model [38]. The fracture toughness of the separation between the segments in serrated chips in high speed machining is then deduced. In addition, an energy conservation equation for high speed machining process, which considers the energy of new created workpiece surfaces, is established. The fracture energy of serrated chips is taken into the developed energy conservation equation. Five groups of experiments are carried out under the cutting speeds of 100, 200, 400, 800 and 1500m/min. The cutting forces are measured using three-dimensional dynamometer and the relevant geometrical parameters of chips are measured with the aid of optical microscope. The experiment results show that the yield stress of machined ductile metal material presents an obviously increasing trend with the cutting speed increasing from 100 to 800m/min while it decreases when the cutting speed increases to 1500m/min further. Meanwhile, the fracture toughness between the chip and bulk material displays a slightly increasing tendency. In high speed machining, the fracture toughness of the separation between the segments in serrated chips also presents increasing trend with the increasing cutting speed, whose value is much greater than that between the chip and bulk material. In the end, the distribution of energy spent in cutting process is analyzed which mainly includes such four portions as plastic deformation, friction on the tool–chip interface, new generated surface and chip fracture. The results show that the proportion of plastic deformation is the largest one while it decreases with the cutting speed increasing. However, the proportions of energy spent on new created surface and chip fracture increase due to the increasing of both the chip's fracture area and the fracture toughness.

Microstructural characteristics and tensile properties of nano-composite Al 2014/4 wt.% Al2O3 produced from machining chips

Fine Al 2014 powder reinforced with Al2O3 nano-particles was produced by milling the large strained machining chips. Powder was extruded and subsequently solution treated and aged. Microstructure evolution during different stages of deformation was studied by X-ray diffraction (XRD). The average grain size of the 48h milled Al 2014 powder was calculated as 26nm. After hot extrusion the grain size was 85nm. In addition, the dislocation character and density of the material and their evolution during processes were studied. The yield strength of the nano-composite Al 2014/4wt.% Al2O3 was 405MPa which is almost 100MPa higher than a conventionally T6 heat treated material. Fracture behavior of the produced material is also discussed.