Showing papers in "Journal of Japan Institute of Light Metals in 2004"
35 citations
TL;DR: In this article, the feasibility of ECA compaction with homogeneous mechanical properties at room temperature using equal-channel angular (ECA) pressing was investigated on AZ31B magnesium alloy cutting chips.
Abstract: Experiments have been conducted on AZ31B magnesium alloy cutting chips in order to investigate the feasibility of producing a compaction with homogeneous mechanical properties at room temperature using equal–channel angular (ECA) pressing. Repetitive pressings, consisting of a total of 4 passages through a die at 573 K with and without MoS2 as a lubricant, were conducted on each sample. After the initial pressing of each sample was completed the samples were rotated 90 degrees and pressed again. This pressing procedure was repeated two more times for all four samples. It was shown that ECA pressing without lubricant was capable of obtaining the compaction with crack–free smooth surfaces after a single pressing. This was most likely because after pressing, a thin, continuous surface layer is created by the heavy shear strain caused by the resulting friction constraint from the die surface. The FEM analysis confirmed the heavy shear strain distribution in the surface layer of the compaction after the single pressing without lubricant. Grain refining after the pressing was observed via the TEM. However, the mechanical properties at room temperature were not homogeneous even after repetitive pressings up to a total of 4 passages through a die. Contrary to the non–lubricated samples, samples that were ECA pressed using lubricant did not display the thin shear strained surface layer. The lack of the distributed shear strain surface layer was most likely caused by a lower coefficient of friction created by the MoS2 lubricated die. Experimental procedures also concluded that the pressing force required for the lubricated samples was remarkably low in comparison with that for the non–lubricated pressings. However, surface crack formation could not be avoided during the pressings that utilized the lubricated ECA pressing process. It was shown that a combined ECA pressing process consisting of an initial pressing without lubricant followed by repetitive pressings up to a total of 3 passages with lubricant was an effective method for producing a compaction with homogeneous mechanical properties at room temperature under low pressing force.
19 citations
TL;DR: Grain refinement in a magnesium alloy AZ31 was studied in multi-directional forging (MDF) with decreasing temperature from 623 K to 423 K and at a strain rate of 3×10−3 s−1 as mentioned in this paper.
Abstract: Grain refinement in a magnesium alloy AZ31 was studied in multi-directional forging (MDF) with decreasing temperature from 623 K to 423 K and at a strain rate of 3×10−3 s−1 The MDF was carried out up to large cumulative strains with changing the loading direction during decreasing temperature from pass to pass The structural changes are characterized by the generation of many mutually crossing kink bands at low strain, followed by the development of very fine grains at large strains The dynamic change in grain size can be expressed by two different power law functions of flow stress for the region of flow stress above or below 100 MPa The MDF with decreasing temperature can accelerate the uniform development of much finer grains and the improvement in plastic workability, leading to the minimal grain size of 023 μm at 423 K The mechanism of grain refinement is discussed in detail
17 citations
TL;DR: In this paper, the interdiffusion experiments of Ti-rich β Ti-Al-Cr alloys have been performed in the temperature range from 1273 to 1473 K. The diffusion paths show S-shaped curves.
Abstract: The interdiffusion experiments of Ti-rich β Ti–Al–Cr alloys have been performed in the temperature range from 1273 to 1473 K. The concentration profiles indicate that the diffusion distance of Cr is somewhat longer than that of Al in the solid solutions. The diffusion paths show S-shaped curves. The formation of S-shaped diffusion paths is attributed to the difference between the diffusion distance of Cr and Al. The direct and indirect interdiffusion coefficients are positive in the ternary alloys, and the four interdiffusion coefficients are not sensitive to the solute concentrations. The ratio of indirect coefficient to direct one suggests that repulsive interactions exist between Al and Cr atoms in the Ti–Al–Cr alloys. In addition, the ratio values of converted interdiffusion coefficients in the ternary alloys suggest that the interactions between Ti (solvent) and Cr atoms are attractive in the present alloy.
17 citations
TL;DR: In this paper, resistance spot welding was applied to make a dissimilar-metal joint between Mg alloy AZ31B plate and commercially pure Al plate, and the effect of Ag insert on the joint strength was investigated.
Abstract: In this study, resistance spot welding was applied to make a dissimilar-metal joint between Mg alloy AZ31B plate and commercially pure Al plate. Factors affecting the cross tensile strength of the joint and the effect of Ag insert on the joint strength were investigated. The main results obtained in this study are as follows.The strength of the dissimilar-metal joint of Mg/Al increased with increasing welding current, however, the strength was very low and was about one forth to one fifth that of the similar-metal joint of Mg/Mg made under the same condition.By using insert metal consisting of four layers of Ag foil with 0.1 mm thickness, the strength of the Mg/Ag joint increased about 1.5 times than that of the Mg/Ag joint without the insert metal.With increase in the thickness of the foil-layered Ag insert metal, the thickness of an intermetallic compound formed at the interface between Mg and Ag decreased and the thickness of a eutectic reaction layer between Ag and Al increased, resulting in the increase in the Mg/Al joint strength. However, when the insert metal of 5-layers Ag foil was used, the strength of the Mg/Ag joint decreased because non-bonded regions occurred in the eutectic reaction layer.
15 citations
TL;DR: In this paper, the tensile properties at room temperature and the surface quality of the extrusions were evaluated for both AZ31B and AZ91D magnesium alloys for recycling of cutting chips.
Abstract: Hot extrusion tests for the purpose of recycling of cutting chips were carried out for AZ31B and AZ91D magnesium alloys. The tensile properties at room temperature and the surface quality of the extrusions were evaluated. Excellent mechanical properties at room temperature were obtained for an extrusion temperature of 423 K for AZ31B and for 573 K for AZ91D alloy, respectively. The tensile strength and yield strength of AZ31B cutting chip extrusion were higher than those of the extrusion from AZ31B cast billet, probably due to a grain refinement effect. However, the peculiar and wavy surface roughness almost perpendicular to the extrusion direction was formed in the extrusions from cast billet as well as in the extrusions from cutting chips of both alloys. On the extrusion surface of AZ31B alloy cutting chips, a mixed texture of basal and non-basal planes was formed. Moreover, a strong basal plane texture was observed in the layer approximately 0.4 mm from the surface. Discontinuous metal flow due to the difficulty of basal plane slip along the die exit corner with a sharp rectangular edge appeared to form the peculiar and wavy surface roughness.
14 citations
TL;DR: The effect of using an insert metal on the microstructures and mechanical properties of the dissimilar friction welded joint was investigated in this paper, where a continuous drive friction welding machine was used to fuse 5052 aluminum alloy to pure titanium.
Abstract: 5052 aluminum alloy to pure titanium were friction welded using a continuous drive friction welding machine. Effect of using an insert metal on the microstructures and mechanical properties of the dissimilar friction welded joint was investigated. Friction welded joints without insert metal were observed compound layer and the thickness of intermetallic compound layer were irregular and thick. Friction welded joint with insert metal, its compound layer became thin and generated comparatively evenly. In spite of the existence in the friction welding of the use of the insert metal, the hardness of compound layer of both welded joints showed higher than those of the both base metals. Tensile strength of welded joint without insert metal showed 78% of 5052 aluminum alloy and it's fractured at weld interface. But, in case of welded joint using an insert metal, the tensile strength showed 92% of 5052 aluminum alloy. The elongation of welded joints with insert metal was improved. All the welded joints with insert metal were fractured at softened area of heat affected zone of 5052 aluminum alloy side in tensile test.
12 citations
TL;DR: In this paper, the effect of natural aging conditions on split aging, especially bake hardenability at 170°C for 1.2 ks and 86.4 ks on Al-Mg-Si alloys have been studied using hardness measurement, DSC analysis and electrical resistance measurement.
Abstract: Effect of natural aging conditions on split aging, especially bake hardenability at 170°C for 1.2 ks and 86.4 ks on Al–1%Mg2Si, Al–1.5%Mg2Si and Al–1%Mg2Si–0.6%Si alloys have been studied using hardness measurement, DSC analysis and electrical resistance measurement. The increasing hardness of an Al–Mg–Si alloy with excess Si during baking at 170°C for 1.2 ks without natural aging is higher than that of Al–Mg–Si alloys without excess Si. However, the hardness of the high Si content alloy after baking at 170°C for 1.2 ks was decreasing with increasing natural aging time before baking clearly. It could be considered that the cluster which did not transfer to β″ phase formed using vacancy during natural aging on the high Si content alloy. The β″ phase of the high bake hardenability sample on DSC analysis appeared at lower temperature compared with the low bake hardenability sample. The β″ phase which was located at lower temperature on DSC analysis precipitates quickly during bake at 170°C, and the hardness was increased during baking at 170°C for 1.2 ks.
12 citations
TL;DR: In this article, the structure and passivity of the films formed on magnesium in alkaline solutions containing aluminate ions were evaluated by using various methods including electrochemical measurements and a field emission scanning electron microscope.
Abstract: Structure and passivity of the films formed on magnesium in alkaline solutions containing aluminate ions were evaluated by using various methods including electrochemical measurements and a field emission scanning electron microscope. When concentration of sodium ions was kept constant, increase in aluminate ions effectively depressed the peak current at around 5 V and increased the breakdown voltage. This is caused by the improvement of surface passivity of magnesium and oxide protectively. Aluminum content incorporated in the film lineally increased with log of increasing concentration of aluminate ions added in the solution. However, besides the concentration of aluminate ions in the solution, the corrosion resistance evaluated by salts spray test was highest in the thick films formed at around 5 V with extremely high current density. Further, it is clarified that all films formed at 5 V exhibit vertical cylindrical cellular structure similar to the Keller model of porous anodic alumina.
12 citations
8 citations
TL;DR: In this article, the effects of the zincate pretreatment and heat aftertreatment on adhesion of electroless Ni-P coating onto aluminum alloy substrate were examined, and the double zincate treatment markedly improved the adhesion between aluminum Alloy substrate and Ni−P coating.
Abstract: In this study, we have examined the effects of the zincate pretreatment and heat aftertreatment on adhesion of electroless Ni–P coating onto aluminum alloy substrate.The precipitation state of zinc was differs with the number of zincate treatment, and the double zincate treatment markedly improved the adhesion between aluminum alloy substrate and Ni–P coating. This adherent improvement can be attributed to metallurgical bond occurred by the diffusion between aluminum alloy substrate and Ni–P coating under the plating temperature (363 K×7.2 ks).
TL;DR: In this paper, the surface roughness of aluminum alloys (A2017, A5052), stainless steel (SUS304), and copper alloy (nickel silver C7541) was evaluated by using surface color analysis.
Abstract: In this paper, we carried out an experimental research for establishing the evaluation of metal's surface texture by analysis of surface color. The materials of samples used in the experiment were aluminum alloys (A2017, A5052), stainless steel (SUS304) and copper alloy (nickel silver C7541). The surfaces of samples were burnished by use of waterproof abrasive papers. The surface roughness of samples evaluated by arithmetical mean Ra, root mean square slope RΔq and mean width of the profile elements RSm. The experimental results showed strong correlation for three different roughness parameters. Consequently, “Ra” was used as roughness parameter. As Ra decreased, the glossiness exponentially increased. The evaluation method of surface color was applied to CIELAB. The lightness L* in CIELAB decreased as Ra decreased. Thus, it showed that relationship between L* and Ra inverse correlation between glossiness and Ra. Moreover, surface color of four different materials showed that the chromaticness of blue increased as Ra decreased.
TL;DR: In this paper, the authors applied the Fast Fourier Transform (FFT) method to evaluate a repeated load drop (serration) observed in the load-time curves in the tensile test.
Abstract: Fast Fourier Transform (FFT) method was applied in order to evaluate a repeated load drop (serration) observed in the load-time curves in the tensile test. 5083 aluminum alloy plates were tested in tension at temperatures between 203 K and 333 K using an Instron type tensile test machine. Changes in repeated load drops with the deformation temperature were characterized by a conventional method (mean amplitude ΔLm and number N of load drops) and FFT method (maximum amplitude Cmax and peak frequency fp derived from the Fourier spectrum). Cmax and fp were compared with ΔLm and N, respectively. The comparison showed the reasonable agreement between fp and N, as well as that of Cmax and ΔLm. In evaluation of the serration using FFT method, there was no artificial reading error and reliable analysis could be carried out in a short time. Therefore it suggests that FFT method is suitable for the investigation of the serration.
TL;DR: In this paper, the authors proposed a new alloy with higher Cu content, which gives higher strength than that of commercial Mesoalite 20, and they showed that the compressive strength and plastic elongation to fracture decreased with increasing Mn content.
Abstract: The super high strength Al–Zn–Mg based alloy (Mesoalite20®) with a chemical composition of Al–9.5Zn–3Mg–1.5Cu–4Mn–0.5Zr–0.02Ag in mass% includes two type of precipitates of Q and Al6Mn phases. The Q precipitates have a quaternary composition and fine rod-like shape, but Al6Mn has round and irregular shape. After compaction of air-atomized powder by CIP, the Q and Al6Mn phases precipitated in sequence during heating. By hot extrusion at 773 K, their precipitates flowed along extrusion direction and only Q precipitates aligned well, which have been known to be very effective to fiber-reinforcement. When increasing Mn content from 4 to 7 mass% with constant of 1.5 mass% Cu, the amount of Al6Mn increased remarkably. Consequently the compressive strength and plastic elongation to fracture decreased with increasing Mn content. When increasing Cu content from 0.5 to 2.5 mass% with constant of 4 mass% Mn, on the other hand, the amount of Q phase increased and their mechanical property improved slightly with increasing Cu content. Therefore the present study has proposed a new alloy with higher Cu content, which gives higher strength than that of commercial Mesoalite 20.
TL;DR: In this paper, the authors proposed a method to improve the quality of air quality by using Secondary Aluminum Maximum Achievable Control Technology Standards (SACTS) standards. But this method is not suitable for outdoor applications.
Abstract: アルミニウム合金の半連続鋳造ラインでは,保持炉内で脱 アルカリ金属,脱水素ガスおよび脱介在物を目的とした溶湯 処理が行われる。一般には黒鉛製のランスパイプを多数本用 いて,Arや N2の不活性ガスと Cl2ガスを混合して溶湯中に 吹込む方法が広く採用されている。しかし,この方法ではガ ス気泡サイズが大きいために処理効率は低く,吹込まれたCl2 ガスのほとんどがそのまま湯面から排出されて,その一部は 炉内の水蒸気と反応してHClガスとなる。これらの塩素系ガ スは周辺環境を著しく悪化させる要因となり,特にダイオキ シン類発生の原因物質と考えられている。このため,米国で は大気清浄化法(Clean Air Act)のもと,2000年 3月に第 2 次 MACT基準( Secondary Aluminum Maximum Achievable Control Technology Standards)が制定され,鋳造ラインで発生 する HClガスや粒子状放出物に関する規制が強化された 。 また,日本国内でも日本アルミニウム協会の主導により Cl2 ガス使用量の低減が業界目標に取上げられている。 このような Cl2ガス使用量低減の世界的な傾向により,溶 湯処理に用いる塩素の反応効率向上が不可避となり,また, フラックスへの切替えの検討も始まっている。そのため,こ こでは Cl2ガス代替としての溶湯精練用フラックスによる保 持炉内の溶湯処理技術に関して,フラックス成分やその特 徴,精練メカニズムおよび精練性能を整理してまとめた。 2.溶湯精練用フラックスの成分と特徴
TL;DR: In this article, the formation behavior and structure of newly established anodic films grown on pure magnesium and AZ alloys were studied in organic electrolyte containing 1 mol·dm−3 triethylamine/ethylene glycol solution with varying water content.
Abstract: Formation behavior and structure of newly established anodic films grown on pure magnesium and AZ alloys were studied in organic electrolyte containing 1 mol·dm−3 triethylamine/ethylene glycol solution with varying water content. The growth behavior and appearance of anodic films were significantly affected by water content. In the region between 10 and 30% of water content, compact barrier-type films were obtained both 99.6% Mg and AZ91D. The surface appearance of obtained films was transparent, which was different from those formed usually in aqueous solutions. In addition, these films possessed a high order of corrosion resistance. In the case of electrolyte containing water below 10% or 50%, the appearances were yellowish white and whitish gray, respectively. The composition of anodic films determined by FT-IR and GD-OES analysis showed the incorporation of organic substance into the anodic film. The amount of incorporated organic species increased with decreasing water content in the electrolyte.
TL;DR: In this paper, the photocatalytic activity of a thin film formed on 5083 aluminum alloy (TiO2/5083) sheets by using the advanced sol-gel method, and the effect of anodic oxide film between TiO2 thin film and 5083 alloy sheets were investigated by evolution of photocatalysis activity, X-ray diffraction (XRD) technique, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS).
Abstract: The photocatalytic activity of TiO2 thin film formed on 5083 aluminum alloy (TiO2/5083) sheets by using the advanced sol-gel method, and the effect of anodic oxide film between TiO2 thin film and 5083 alloy sheets were investigated by evolution of photocatalytic activity, X-ray diffraction (XRD) technique, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The photocatalytic activity of TiO2/5083 sheet was low and MgO was detected by XRD and TEM. The photocatalytic activity of TiO2/5083 sheet with anodic oxide was improved and was higher than that of TiO2/5083 sheet without anodic oxide film. It was confirmed by XRD, SEM and high resolution TEM that MgO was not detected in the TiO2 thin film with anodic oxide film between TiO2 thin film and 5083 sheet. It has been considered that the sheet which has anodic oxide film between TiO2 and 5083 sheet did not have MgO.
TL;DR: In this paper, the SCC resistance of hot-extruded P/M Al-Zn-Mg alloys, Mesoalite, was investigated as compared with that of I/M alloys and the correlation between stress corrosion resistance and micro abstracture was studied.
Abstract: The stress corrosion cracking (SCC) resistance of hot-extruded P/M Al–Zn–Mg alloys, Mesoalite, was investigated as compared with that of I/M Al–Zn–Mg alloys and the correlation between stress corrosion resistance and microstracture was studied. SCC resistance about P/M alloys was high as compared with that of I/M alloys and when the solute concentration increased, reduction of SCC resistance about P/M alloys was not observed. The difference in width of PFZ, distribution of precipitates on grain boundary, the amount of metastable phase precipitated in the matrix, tilt angle of grain boundary, grain size and shape was investigated as a cause of the difference of SCC resistance. The large change in the size and shape of grain among these factors was observed. In the P/M alloys, the fiber-like grain elongated to the extruded direction was observed to the equi-axial grain having been observed in the I/M alloys. When stress was applied parallel to elongated grains, the stress perpendicular to the grain boundary was low. Since the SCC resistance is improved when the applied stress perpendicular to the grain boundary is small, it is concluded that the SCC resistance of the P/M alloys which has the fiber-like grain elongated to the ED became large.
TL;DR: In this paper, resistivity of a sample containing 7.8 to 8.6 mass% Zn increased with descending temperature treatment starting from 673 K and saturated at 633 K.
Abstract: Eutectically solidified portion, which should be liquid at 673 K, remained in alloys containing more than 7.8 mass% Zn. From change in area fraction of the liquid phase with Zn content, boundary composition between L+α and α regions at 673 K was estimated as about 6.7 mass% Zn. Resistivity of a specimen containing 7.8 to 8.6 mass% Zn increased with descending temperature treatment starting from 673 K and saturated at 633 K. Treatment at 613 K, the reported eutectic temperature, prolonged for 602 ks gave a nearly same saturating resistivity which suggested a maximum equilibrium solubility of Zn to Mg to be about 8.5 mass%. Details to be paid attention are described for resistivity measurement of large cross section specimens requiring a large electric current to generate enough electromotive force. When the resistance was measured in liquid nitrogen, effect of Joule heat was scarcely observed. The heating effect was clearly observed when the resistance was measured in a kerosin bath. Even in this case, the effect can be eliminated easily by extrapolation of square of current versus measured resistance plots to zero current.
TL;DR: In this article, the authors used heat transfer between the sheet and a couple of heated metal dies to prepare a peripherally softening blank for deep drawing, and found that the aluminum blank could be heated to the temperature of the heated dies by contacting with them in less than 1 s and the temperature gradient more than 20 degrees/mm could be obtained near the contacting region.
Abstract: Partial softening heat treatment of aluminum alloy sheets was investigated using heat transfer between the sheet and a couple of heated metal dies to prepare a peripherally softening blank for deep drawing. It was found, from the heat conduction analysis, that the aluminum blank could be heated to the temperature of the heated dies by contacting with them in less than 1 s and the temperature gradient more than 20 degrees/mm could be obtained near the contacting region. The temperature of the sheet contacted with the heated dies depends on heat transfer from the heated dies and the temperature recovery of their surfaces. Production of the peripherally softening blanks was examined for 5052-H24, 1100-H24 and 6061-T6 aluminum alloy sheets. In the blank of 6061 aluminum alloy sheets, the difference in hardness of the central hard part and the peripheral soft part was about 1.8 times. The softening region was changeable according to inner diameters of the heated dies.
TL;DR: In this article, the increase in resistivity by low temperature aging of Mg-Zn binary and ZK60 alloys was quantitatively investigated, and a relation between composition and aging temperature was proposed for formation limit of G.P. zone which increases the resistivity.
Abstract: Though G.P. zone formation had been widely recognized in Mg–Zn binary alloys, there still remained some ambiguity in resistivity increase by low temperature aging. Applying the previously improved method of reliable resistivity measurement, the increase in resistivity by low temperature aging of Mg–Zn binary and ZK60 alloys was quantitatively investigated. After solution treatment at 673 K for 86.4 ks, Mg–4~10mass%Zn alloy specimens sampled from ingots were aged at low temperatures below 373 K. The resistivity increase by aging at room temperature (R.T.: about 295 K) shows a clear and very long incubation period in all alloys and does not attain the peak until 40 Ms (1.25 year) aging. In the Mg–4mass%Zn alloy, the resistivity increase is not detected by the R.T. aging till 6 Ms. Because the ZK60 alloy containing 4.84%Zn shows a slight increase from 1 Ms, the incubation period of Mg–4mass%Zn alloy may be longer than 10 Ms. The highest aging temperature at which the resistivity increase due to G.P. zone formation is observed was 333 K. Very sharp resistivity peak on isothermal aging curve accompanying with a steep decrease is quite different from that of Al–10mass%Zn alloy. Up to the resistivity peak, a tendency is confirmed that the gradient of DMR corrected Matthiessen plot is smaller than that corresponding to precipitation of transition phases. Maximum increment in resistivity from as solution treated states is large in high alloys and low aging temperatures. Using these dependences of the maximum increment on solute concentration and aging temperature, a relation between composition and aging temperature is proposed for formation limit of G.P. zone which increases the resistivity.
TL;DR: In this article, the corrosion characteristics of aluminum power cable on which the intermetallic phase were successfully removed by the cathodic treatment in a 20% nitric acid solution at current density of −2 kA/m2 were examined in a 1.0 kmol/m3 NaCl solution.
Abstract: The corrosion characteristics of aluminum power cable on which the intermetallic phase were successfully removed by the cathodic treatment in a 20% nitric acid solution at current density of −2 kA/m2 were examined in a 1.0 kmol/m3 NaCl solution. It was found that the FeAl3 free surface of aluminum power cable by the treatment showed corrosion behavior of high purity aluminum. Electrochemical measurements revealed that the FeAl3 free surface coated by the anodizing finishing treatment exhibits excellent oxide film performance.
TL;DR: In this paper, a model for the precipitation behavior of impurity Fe and Si in commercial purity aluminum was presented under the nucleation and growth theory, and the equilibrium stability and solvus temperature of precipitates were determined by thermodynamic calculation for Al-Fe-Si alloys.
Abstract: Microstructure and precipitation control for optimizing processing conditions is vitally important for improvement of quality of wrought aluminum alloys. In this study, a model was presented for the precipitation behavior of impurity Fe and Si in commercial purity aluminum. The model was basically constructed under the nucleation and growth theory. The equilibrium stability and solvus temperature of precipitates and equilibrium solvus boundaries of Fe and Si in solid solution were determined by thermodynamic calculation for Al–Fe–Si alloys. The temperature–time-precipitation (TTP) curves for Al3Fe and α-AlFeSi were mainly described in this paper. In addition, as the effects of strain-induced precipitation, a stored energy term was added to the rate of heterogeneous nucleation, in which the effects of recovery and recrystallization were taken into account.As an experimental verification of this model, the changes in solute Fe contents during isothermal annealing in the un-deformed and hot-deformed specimens were quantitatively investigated by chemical analysis of extracted residue with phenol (phenol residue method). The present model quantitatively explained the experimental results, in particular, concerning TTP curves and the accelerated precipitation due to strain.
TL;DR: In this article, the authors proposed up-grade recycling techniques in which severe plastic deformation in room temperature air is utilized to cutting chip mixture of dissimilar materials, thereby consolidation and further accumulation of strain are simultaneously achieved.
Abstract: The present authors have realized that cutting chips may be identified utilizable for the strengthening of materials due to large plastic strain accumulated during cutting. The authors have proposed up-grade recycling techniques in which severe plastic deformation in room temperature air is utilized to cutting chip mixture of dissimilar materials, thereby consolidation and further accumulation of strain are simultaneously achieved. In this study, such composite materials are produced and evaluated with combinations of 6061 aluminum/IF steel and 6061 aluminum/pure copper. It is clarified that appropriate second phase cutting chip is a BCC metal. The ultimate tensile strength of the 6061 alloy is improved approximately up to 500 MPa (about 1.6 times that of the material before cutting) when the volume fraction of the IF steel is 20%. To predict the attainable maximum tensile strength by the current method, the Eshelby equivalent inclusion model is employed. The present method is identified to have a potential of realizing 713 MPa (about 2.3 times that of the material before cutting) in the case of the 6061 alloy/20%IF steel composite by eliminating production defects adjusting the matrix/second phase combination and conditions for cutting and plastic working.
TL;DR: In this article, the behavior of Mn in billet of 6082 aluminum alloys was investigated by absolute value measurement of resistivity and direct analysis of solute Mn concentration, which indicated that 57~75% of added Mn is found to be in solid solution.
Abstract: Behavior of Mn in billet of 6082 aluminum alloys was investigated by absolute value measurement of resistivity and direct analysis of solute Mn concentration. In as cast state, 57~75% of added Mn is found to be in solid solution. Heating up to the homogenization temperature, 823 K, was simulated by accumulative isochronal heat treatment with temperature and time interval 50 K/5.16 ks. Precipitation of Mg–Si compounds was detected from 473 K and attained maximum at 573 K, separated from the starting and maximum temperatures for precipitation of Al–Mn–Si compounds, 673 K and 773 K, respectively. Average diffusion distance of solutes, which was estimated from impurity diffusion data, ranged from 10 to 100 nm at the starting temperature of the each precipitation. Solute Mn concentration at 823 K is extremely lower than equilibrium solubility of Al–Mn binary system because of coexistence with Si. Above results suggest that the added Mn precipitates for most part during homogenization, therefore total amount of the insoluble particles containing Mn will be changed little by preheating and hot extrusion, except shape and dispersion of the particles. Thus, it can be predicted that resistivity and hardness changes during cooling after the homogenization or by various heat treatments after the extrusion are mainly caused by the change in Mg+Si concentration or amount of Mg–Si precipitates.
TL;DR: In this article, an incremental in-plane bending machine using numerical control technology and bending experiments are carried out and some experimental results such as beating force, bending radius, strain distribution are experimentally examined.
Abstract: Incremental in-plane bending which has been invented by authors is a new and flexible manufacturing technology for small-lot production of sheet metal with various bending radii. The sheet metal is bent incrementally by an inclined-punch beating. The prototype incremental bending machine uses the numerical control technology and bends the sheet metal flexibly. The bending experiments are carried out and some experimental results such as beating force, bending radius, strain distribution are experimentally examined. The forming properties of in-plane bending are clarified in this study. Moreover, approximate formulas for calculating the bending radius are proposed base on the plane strain. The bending radius calculated by the proposed formula agrees with the one of the experiments.
TL;DR: In this paper, the surface composition of hard-coated die after 5 extrusions was analized by ESCA and the roughness of the coated area with TiAlN films hardly changed after 5 extrusions.
Abstract: Resistance of wear and oxidation of hard-coated die for aluminum extrusion is investigated. Nitrided layer was prepared by radical nitriding method, and the 3 μm hard coat films, CrN, TiN, TiAlN and TiAlCrN, were prepared by arc ion plating. Hardness, friction coefficient, critical load and roughness (Ra) of hard-coated specimens (SKD61) were observed before and after oxidation at atmosphere, 500°C-5 h. Roughness (Ra) of coated area of die before extrusion and after removal of adhesive aluminum were compared. Surface composition of coated area after 5 extrusions were analized by ESCA. In the case of nitrided die, whole coated area was oxidized, scraches (depth: 2 mm, width: 20 μm) had occurred in the direction of extrusion and roughness (Ra) was increased after 5 extrusions. On the contrary, the roughness of the coated area with TiAlN films hardly changed after 5 extrusions. TiAlN coated die showed higher durability in comparison with dies coated with nitrided, because of the higher oxidation resistance of TiAlN.