Machining Chips Research Articles

Friction stir welding of recycled A6061 aluminum plates fabricated by hot-extrusion of machined chips

An excellent process for saving energy and resources is the ‘solid phase recycling process’ [1–5], since it can process material at lower temperatures and with a higher recycled product yield than the more common remelting processes used currently. This technique consolidates machined chips in the solid phase by a hot-extrusion process. Lightweight metals made by the solid phase recycling process have a fine structure due to severe plastic deformation during the production process. Material shapes, however, are restricted to thin solid cylinders or narrow strips because of processing constraints. Therefore, in order to make large-size components it is necessary to use secondary processing such as joining. Generally, melting-type welding methods are employed for joining lightweight metals. These methods, however, significantly impair the structure because of inevitable grain coarsening and segregation of alloying elements. Friction Stir Welding (FSW) has emerged as a new solid state joining technique [6], especially for aluminum alloys [7–14]. In this process, a rotating tool travels down the length of contacting metal plates, and produces a highly plastic deformed zone through the associated stirring action. Friction between the tool shoulder and the plate top surface produces a localized heating zone, an addition to the plastic deformation of the material brought by contact with the tool. In this research, solid phase recycled materials were friction stir welded in the solid state in order to obtain plate materials with superior mechanical properties. The structure of FSW specimens was analyzed using a scanning ion microscope (SIM, Seiko Instruments Inc. SMI-2000) and a transmission electron microscope (TEM, Hitachi, Ltd. H-800). Fig. 1 shows machined chips of A6061. These were prepared by machining an extruded A6061 rod using a lathe with no lubricant. The machined chips were encapsulated in a pure aluminum can, and extruded with an extrusion ratio 1:4 at 873 K. As a result, cylindrical recycled materials with a diameter of about 20 mm were obtained. The materials were rolled perpendicular to the extrusion direction (in the diametral direction) at 673 K to give plate specimens 100 mm × 60 mm × 4 mm in size. Specimen surfaces that contacted the

Vacuum Foaming of Magnesium Slurries

A new production route for metallic foams the vacuum foaming technique (VFT), is presented. The principle of this technique is based on the expansion of gas pores in metal melts at low pressure. As starting materials high pressure die casting scrap and machining chips are used.

Primary chip formation during the micromachining of engineering materials

The advent of nanotechnology has created a demand for precision-machined substrates so that ‘bottom-up’ nanomanufacturing processes can be used to produce functional products on the nanoscale. However, machining processes must be scaled down by an order of magnitude that requires very stable desktop machine tools to produce precision-machined substrates. Therefore, the mechanics of chip formation at this scale is critical when the effect is considered of chip formation on the generation of surface roughness on the substrate. The tight curl of a machined chip in orthogonal machining appears to be part of the primary shear process. It is also known that transient tight curl occurs before a secondary shear zone develops ahead of the removal of the chip from the cutting zone. However, continuum models predict that curled chips incorporate stresses due to the establishment of a secondary shear zone. A model is presented in terms of the heterogeneous aspects of continuous chip formation, which shows very good agreement with experimental data.

Ｍｇ‐Ａｌ‐Ｚｎ系合金切削チップ熱間押出材の表面性状の改善

In order to recycle machined chips, hot extrusion tests were performed on magnesium alloys AZ31B and AZ91D. Two types of extrusion dies were used—one with an exit corner having a sharp rectangular edge (N-die) and the other with an exit corner having a round edge (R-die); the radius of the round edge was 1.5 mm. In the extrusion tests using N-die, peculiar and wavy surface roughness that was almost perpendicular to the extrusion direction was formed in the extrusions obtained from machined chips of both the alloys. This roughness appears to be due to discontinuous metal flow caused by the basal plane slip along the exit corner of N-die. Therefore, the exit corner of R-die was essentially effective in improving the surface roughness of the extrusions because it led to smooth and continuous metal flow. The surface roughness tended to decrease with an increase in the extrusion ratio R from 19 to 100. Grain boundary sliding in the extrusion surface layer at the die exit appears to be a possible mechanism of another type of surface roughness, particularly in the extrusion tests performed with lower extrusion ratios, i.e., at lower strain rates.

切削チップを用いたＭｇ‐Ａｌ‐Ｚｎ混合粉末のメカニカルアロイングにおける生成相

An aluminum and a zinc powder were mixed to machined chips of AZ31 alloy with various contents, and then the powder mixtures were mechanically alloyed for various milling times using planetary ball mill, for the purpose of recycling of the magnesium alloy. Crystal phase formed in the obtained powder were investigated by X-ray diffraction and Vickers hardness of the powder particles to confirm the formed phases. When Mg-Al system powder mixture was milled for 72 ks by the planetary ball mill, super-saturated solid solution α-Mg and intermetallic compound Mg17Al12 phase are formed, while by milling using the oscillatory ball mill 54 ks was necessary. In the case of mechanically alloyed Mg-2.5 mol% Zn powder, super-saturated α-Mg phase with 2.5 mol% Zn concentration forms. The structures of Mg-28 and 52 mol% Zn powder obtained by the mechanical alloying consist of Mg2Zn2 or MgZn2 and Mg7Zn3 phases and then these phases became amorphous by milling for further time. In the case of mechanical alloying for ternary Mg-Al-Zn system, an icosahedron Mg49(Al,Zn)32 phase, the quasi crystal, forms by the milling for 72 ks in the composition range as following; (30-50)mol% Mg with Al/Zn=(90/10-60/40) molar ratio, Mg-(30-50)mol% Al-20 mol% Zn and Mg-(10-30)mol% Al-40 mol% Zn.

Crystal Structure Formed in Mechanical Alloying Process of Mg-Al-Zn Powder Mixture Using Magnesium Alloy Machined Chips

Crystal Structure Formed in Mechanical Alloying Process of Mg-Al-Zn Powder Mixture Using Magnesium Alloy Machined Chips

Mechanical properties and microstructures of 1100 aluminum subjected to dry machining

Commercial purity 1100 aluminum samples with an initial grain size of 4.6 μm were subjected to dry orthogonal cutting, i.e., without using cutting fluid. The strain distributions in the deformed material ahead of the cutting tool tip were estimated using a metallographic method based on the observation of shear angles. Local flow stress values were estimated using microhardness measurements. Deformation structures developed in the material ahead of the tool tip were investigated at four different locations using transmission electron microscopy (TEM). The microstructure in the primary deformation zone (PDZ) was characterized by elongated subgrains, extending in the direction of the strain gradient. The average thickness of the subgrains was 380 nm and their width was 730 nm. The hardness of the PDZ was 80 kg/mm2, which represented an increase of 80% from the initial hardness. The strains in the machined chips (MC) reached a high value of 2.3. The corresponding microstructure consisted of a mixture of elongated subgrains with dimensions similar to those observed in the PDZ, and recrystallized equiaxed grains with diameters ranging between 25 and 75 nm. This was accompanied with an 8% decrease in the hardness of the MC compared to that of the PDZ. Grain growth occurred in the secondary deformation zone (SDZ) resulting in large equiaxed grains of 1.2 μm in diameter. The use of cooling fluid during machining restricted grain growth in the SDZ by limiting the grain size to 360 nm.

Mechanical properties and microstructures of 1100 aluminum subjected to dry machining

Abstract Commercial purity 1100 aluminum samples with an initial grain size of 4.6 μm were subjected to dry orthogonal cutting, i.e., without using cutting fluid. The strain distributions in the deformed material ahead of the cutting tool tip were estimated using a metallographic method based on the observation of shear angles. Local flow stress values were estimated using microhardness measurements. Deformation structures developed in the material ahead of the tool tip were investigated at four different locations using transmission electron microscopy (TEM). The microstructure in the primary deformation zone (PDZ) was characterized by elongated subgrains, extending in the direction of the strain gradient. The average thickness of the subgrains was 380 nm and their width was 730 nm. The hardness of the PDZ was 80 kg/mm 2 , which represented an increase of 80% from the initial hardness. The strains in the machined chips (MC) reached a high value of 2.3. The corresponding microstructure consisted of a mixture of elongated subgrains with dimensions similar to those observed in the PDZ, and recrystallized equiaxed grains with diameters ranging between 25 and 75 nm. This was accompanied with an 8% decrease in the hardness of the MC compared to that of the PDZ. Grain growth occurred in the secondary deformation zone (SDZ) resulting in large equiaxed grains of 1.2 μm in diameter. The use of cooling fluid during machining restricted grain growth in the SDZ by limiting the grain size to 360 nm.

Solid-state recycling for machined chips of iron by hot extrusion and annealing

Solid-state recycling for machined chips of pure iron by hot extrusion at 823 K and annealing at 1073–1273 K was carried out. The as-extruded solid recycled specimen without annealing was fractured prior to yielding at room temperature. However, high ductility was recovered by annealing at 1073–1273 K. This is because the oxides at the interface of the machined chips dispersed in grain by annealing. The annealed solid recycled specimens showed higher yield stress than the annealed virgin extruded specimens. Grain refinement for the solid recycled specimens was enhanced by the high dislocation density in the machined chips, resulting in higher strength in the recycled specimens. Thus, the solid-state recycling is a low energy upgrade recycle process.

Tensile Properties and Blow Forming of 5083 Aluminum Alloy Recycled by Solid-State Recycling

The tensile properties and blow forming characteristics of 5083 Al alloy recycled by solid-state recycling were investigated from the viewpoint of oxide contamination. Three types of machined chip with different volumes were recycled by hot extrusion and hot rolling in air. Oxide layers, which were contaminants from the machined chip surface, were distributed in the extrusion direction for the recycled specimens. Oxygen concentration in the recycled specimens increased with the total surface area of the machined chips per unit volume. From the result of the tensile tests performed at 773 K, the elongation to failure of the specimen made of smaller machined chips was lower, than that of the specimens made of larger machined chips, in spite of their same strain rate sensitivity of 0.5. Similarly, in the blow-forming tests at 773 K, the specimen made of smaller machined chips exhibited a lower formability. The low elongation to failure and formability of the recycled specimens made of smaller machined chips are likely to be attributed to a greater contamination of oxide. Thus, oxide contamination has a detrimental effect on the superplastic properties of recycled Al alloy.

Simulation of High-Speed Machining by Eulerian Solution

Formation of isolated chips in high-speed machining is simulated by Eulerian solution. The machining includes large deformation, material failure, and contact of a tool with a workpiece; therefore, its simulation is a challenging problem. The Eulerian solution is attractive to overcome the above difficulties because the computational meshes are fixed in space and new free surfaces can be generated without a special algorithm. The present work focuses on the simulation of the isolated chips involving material failure due to shear bands. The shear-localized isolated chips in the high-speed machining, which correspond with an actual experiment, can be simulated by the Eulerian solution.

Microstructural Refinement in Steels by Machining

AbstractA study has been made of microstructure and hardness of machining chips created from commercially pure iron and carbon steels. Large shear strains imposed during chip formation in machining are found to produce significant microstructure refinement in the chips, resulting in higher hardness compared to the bulk. Transmission electron and scanning electron microscopy have shown the chips to consist entirely of ultra-fine grain structures with ferrite grain sizes in the range of 100-800 nm. With high carbon steels, the microstructure of the bulk material prior to machining is also seen to have a significant influence on the characteristics of the chip.

Use of Recycled Steel Machining Chips and Aluminum Can Shreds for Synthesizing Iron Aluminide Intermetallic Alloys

Some iron aluminide intermetallic alloys based on Fe 3 Al or FeAl have been synthesized from recycled raw materials of steel machining chips and aluminum can shreds. The former was an industrial waste made at a bearing case maker, and it had a spiral shape and a length less than 1 mm and contained 0.87 wt% C, 0.21 wt% Si, 1.53wt% Cr with some other minor elements. The latter, on the other hand, was made by shredding used aluminum cans, and it had a flaky shape and a edge length of 2 to 3 mm and contained 2.3wt% Mg, 0.36 wt% Fe, 0.88 wt% Mn with some other minor elements. When compacts of the steel and aluminum mixture were heated in a crucible in an argon atmosphere, they exothermically reacted and produced iron aluminide intermetallic alloys. For comparison, similar alloys were produced from pure iron and aluminum by melting them in the same heating apparatus. The bending strength, fracture toughness, Vickers hardness and wear resistance of the alloys synthesized from the recycled raw materials were more excellent than or similar to those of the alloys produced from pure iron and aluminum.

133 青銅切りくずを再利用した焼結摺動材料の開発(OS 粉末加工(2))

Cu-Sn sintered materials were developed by utilizing bronze machined chips. The bronze chips, which were produced by dry-turning of BC3 bar, were mixed with electrolytic copper powder and atomized tin powder. The mixed powders were cold-compacted and then sintered without pressure. The limit of mixing amount of the chips to produce green compacts increased as the size of chips decreased. The sintered density and mechanical properties increased as the mixing amount of chips increased up to 10mass%, but decreased slightly above 10mass%. There was no significant influence of size of chips on the sintered density. Cu-10mass%Sn-20vol%graphite sintered composites, which contained not only the bronze chips but also copper-coated graphite powder, showed low wear and friction under dry sliding conditions.

Machining of a Zr–Ti–Al–Cu–Ni metallic glass

Zr 52.5Ti 5Cu 17.9Ni 14.6Al 10 metallic glass machining chips were characterized using SEM, X-ray diffraction and nano-indentation. Above a threshold cutting speed, oxidation of the Zr produces high flash temperatures and causes crystallization. The chip morphology was unique and showed the presence of shear bands, void formation and viscous flow.

Sub-micrometer structures generated during dry machining of copper

Deformation structures developed in the material ahead of the tool tip in commercial purity copper samples that were subjected to an orthogonal cutting process were investigated using transmission electron microscopy (TEM). The effect of the prior thermo-mechanical treatment has been considered by performing orthogonal cutting tests on hot extruded and fully annealed samples. Results showed that the microstructure of the primary deformation zone (PDZ) was characterized by the formation of elongated dislocation cell structures that were composed of heavily tangled dislocation walls. In the hot extruded samples, this structure was generated as a result of the activation of the pre-existing dislocations, but nucleation of fresh dislocations was needed in the annealed samples. Grain refinement occurred in the chip as a result of the subdivision of the elongated cells into smaller equiaxed sub-micron size (220 nm diameter) grains. Evidence for dynamic recrystallization has been found in the microstructure of the machined chips (MCs). However, calorimetric studies and the microhardness measurements have shown that the sub-micron structures of the machined chips were stable at temperatures up to 180 °C.

A computational approach to evaluate temperature and heat partition in machining with multilayer coated tools

In this paper, analytical models for estimating the interface temperature and heat partition to the chip in continuous dry machining of steels with flat-faced tools treated with multilayer coatings are presented. The database for modeling includes changes in the thermal properties of both workpiece and substrate/coating materials and the Peclet and Fourier numbers occurring at actual interface temperatures. Process outputs involve the average tool–chip interface temperature, the tool–chip contact length, the friction energy and the heat balance between the moving chip and stationary tool. It was found that the heat partition coefficient varies significantly from 0.65 to 0.8 when using multilayer coated tools, and changes from 0.5 to 0.6 for uncoated carbide tools. This implies that the use of multilayer coated tools causes about 30% more heat generated due to friction to be transferred into the moving chip. In general, both power and linear models can be used to estimate the interface temperature.

Development of web-based machining chip breaking prediction systems

The prediction of chip breaking in machining is an important task of automated manufacturing. A chip breaking predictive model has been developed to predict the chip breaking behaviour in steel turning with grooved tools. The model is based on the chip breaking limits theory. A web-based chip breaking prediction system has been developed and presented in this paper with industrial application examples. With the system, the chip breaking range in steel turning with grooved tools can be predicted under different cutting conditions. The experimental data for turning different steel material over a wide range of feed rates, cutting speeds and tool geometry showed agreements with the model prediction. The user-friendly system is accessible through the Internet for the purposes of cutting condition design and tool selection. Also, the system can easily be extended to contain new cutting tools and new workpiece materials with a small number of cutting tests.

Machining Simulation of Ductile Iron and Its Constituents, Part 2: Numerical Simulation and Experimental Validation of Machining

To understand the influence of cast iron microstructure on its machinability, a numerical model that simulates machined material on a microstructure scale was developed. This microstructure-level model assembles individual constituents into a composite material based on microstructural composition, grain size, and distribution. Extensive experimentation was performed to determine strain, strain rate, temperature, and load history dependent material properties. The purpose of this work is to validate the microstructure-level model on machining of ductile iron and two of its constituents: pearlite and ferrite. Orthogonal cutting experiments were conducted of the three materials. The measured chip morphology and machining forces were compared with the model predictions, and a good correlation between them was found.

Fabrication of Porous Magnesium Alloys by Pulse Electric Current Sintering Process Using Machined Chips

Recently, negative changes in the earth’s environment due to high emission of CO2 and energy conservation measures have made it important to reduce the weight of transport vehicles in order to improve fuel efficiency and curtail CO2 gas emission. Therefore, aluminum and magnesium alloys have been used as substitution for steel. More attention is paid to magnesium alloys, which are lighter than aluminum alloys. However, magnesium alloys do not have enough high temperature strength and good ductility. Therefore, numerous studies are being carried out on new alloy development 1–3) and improvement of wrought alloys. 4–6) Presently, aluminum alloys are used in many parts of the vehicle, but magnesium alloys are only used in a few parts. However, suitable magnesium alloys have been developed for diecasting of lightweight automotive power train parts that will help to broaden the application of magnesium alloys. 7) In term of vehicle development and evolution up to date, vehicle collision is now a big danger because the vehicle body has become thin due to lightweight measures to improve vehicle performance. Therefore, attention is being paid to impact absorbing materials from the viewpoint of safety in case there is vehicle collision. Presently, aluminum extruded products are used as impact absorbing materials in vehicles. The aluminum products absorb impact energy continuously when they fail in compression during head-on collision. However, aluminum extruded products are too strong, so their impact energy absorbing ability can only protect the vehicle itself from excess damage, but the impact is still transmitted to the occupants, resulting in fatalities during head-on collision. Therefore, porous materials that can absorb various impacts by changing the amount and size of pores must be developed. The application of porous materials are expected to include weight reduction of vehicles, filters, vibration/