Application Of Equal Channel Angular Pressing Research Articles

Evolution of microstructure, macrotexture and mechanical properties of high strength biomedical TA4 pure titanium during multi-pass ECAP

The application of equal-channel angular pressing (ECAP) to TA4 pure titanium (Ti) results in a fine-grained microstructure. This technique presents an substitute for alloying, delivering enhanced mechanical properties without reducing biocompatibility and corrosion resistance. This study employs scanning electron microscopy (SEM), X-ray diffractometry (XRD), and transmission electron microscopy (TEM) to explore the microstructure evolution and the toughening mechanism of TA4 pure Ti after deformation. ECAP performed at 573 K endows TA4 pure Ti with a uniformly fine-grained microstructure, leading to a significant enhancement in its mechanical properties, exemplified by a yield strength of ∼731.9 ± 2.7 MPa and an elongation of ∼30.8± 1.3 %. While the {0001} basal slip primarily governs the ECAP deformation, the non-basal slip plays an increasingly important role with the increase of passes. The increase of yield strength can be attributed to grain refinement and the modification of the {0001} basal texture. Meanwhile, the improvement of plasticity is related to the strengthening of the {101‾ 0} prismatic texture. These findings offer fresh insights and methodologies for the design and manufacture of high-performance biomedical pure Ti.

Development of high-strength bolt material of Al–Mg–Si alloy by ECAP and various aging treatments

At present, the strength of most of Al–Mg–Si alloy bolts is not enough, and thus highly expected to be increased, for example, to >500 MPa in ultimate tensile strength (UTS). In this study, mechanical strength of A6056 Al–Mg–Si alloy was aimed at improving, without diminishing the elongation, by combined application of equal-channel angular pressing (ECAP) and various aging treatments. Multi-pass ECAP and pre-aging (PA) treatment at 373 K for 1.2 ks was found to be effective in strengthening the bolt material subject to room-temperature storage followed by artificial aging. Especially, PA plus ECAP 2pass treatment exerted the biggest impact on the strength (i.e., 514 MPa in UTS) with a reasonable elongation to fracture (i.e., 16%). Such a high strength and good ductility exceeds minimum requirement for aluminum-made bolts registered in JIS B1057, and thus the developed PA-ECAP 2pass specimen can be utilized potentially as a high-strength bolt material.

Development of mechanical properties in a CaO added AZ31 magnesium alloy processed by equal-channel angular pressing

Processing through the application of equal-channel angular pressing (ECAP) is recognized as one of the attractive severe plastic deformation techniques where the processed bulk metals generally achieve ultrafine-grained microstructure leading to improved physical characteristics and mechanical properties. Magnesium has received much attention to date for its lightweight, high strength and excellent elasticity. Mg alloys with addition of CaO is reported to provide the successful casting procedure without usage of greenhouse gas, SF6, whereas it is generally used for preventing the oxidation of Mg during casting. In the present investigation, a CaO added AZ31 (AZ31-CaO) magnesium alloy was processed by ECAP at elevated temepratures with a few steps of reduction which result in significant grain refinement to ~1.5μm after 6 passes. Compression testing at room temperature demonstrated the AZ31-CaO alloy after ECAP showed enhanced yield strength more than the as-processed commercial AZ31 alloy while both alloys maintained ductility in spite of significant reduction in grain size. The improved strength in the AZ31-CaO alloy was attributed to the formation of fine Al2Ca precipitates which experience breaking-up through ECAP and accelerate the microstructural refinement. Moreover, the preservation of ductility was attributed to the enhancement of strain hardening capability in the AZ31 alloy at room temperature. This study discusses the feasibility of using ECAP to improve both strength and ductility on magnesium alloys by applying the diagram describing the paradox of strength and ductility.

Investigation of Steel 09G2S Processed by Equal Channel Angular Pressing

Severe plastic deformation is a well known procedure for fabrication considerable grain refinement in metal materials. Equal channel angular pressing (ECAP) is one of these severe plastic deformation techniques which allows the receiving of the bulk ultrafine grained (UFG) metals. It is well known that the ECAP method leads to significant improvement of strength of investigated materials, but the fracture mechanisms of UFG metals at low temperature are not enough studied. The investigation was performed on low-alloy constructional steel 09G2S (GOST) after application of ECAP. Fracture toughness tests were performed on Charpy impact testing specimens at low temperature. The experiments demonstrate that ECAP treatment has the effect on increasing of fracture resistance of steel 09G2S at low temperature.

Effect of Equal Channel Angular Pressing on the Pitting Corrosion Resistance on the Aluminum Alloys with/without Anodization

The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of Al (AA1100) and Al-Mg (AA5052) alloy with anodization and without was investigated by means of polarization curves in solutions containing 300 ppm or 0.6 mol/L of Cl- and by surface analysis. In Al and Al-Mg alloy without anodization, the potentials for pitting corrosion were evidently shifted to the noble direction by ECAP process, indicating that this process improves resistance to pitting corrosion. SEM observation revealed that the pitting corrosion occurred near the impurity precipitates and the size of impurity precipitated decreased with ECAP process. The time-dependence of corrosion potential and the polarization resistance determined by AC impedance technique suggested that the formation rate of Al oxide films was increased with ECAP process. The improvement in pitting corrosion resistance of Al and Al-Mg by ECAP seems to be attributable to the decrease in the size of impurity precipitates and the increase in the formation rate of Al oxide films. On the other hand, the time required for initiating pitting corrosion of anodised Al was longer with ECAP than without, indicating improvement in the pitting corrosion resistance by application of ECAP. However, the pitting corrosion of anodized Al-Mg alloy occurred earlier with ECAP than without, showing that the corrosion resistance was worse with ECAP than without. In anodized Al-Mg alloy, cracks occurred in the anodic oxide films during initial corrosion and the cracks were larger with ECAP than without. It is assumed that the pitting corrosion was promoted by the cracks due to the higher internal stress resulting from ECAP.

Effect of equal-channel angular pressing on pitting corrosion resistance of anodized aluminum-copper alloy

The effect of equal-channel angular pressing(ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L AlCl 3 and also by surface analysis. Anodizing was conducted for 20 min at 200 and 400 A/m 2 in a solution containing 1.53 mol/L H 2SO 4 and 0.018 5 mol/L Al 2(SO 4) 3·16H 2O at 20 °C. Anodized Al-Cu alloy was immediately dipped in boiling water for 20 min to seal the micro pores present in anodic oxide films. The time required before initiating pitting corrosion of anodized Al-Cu alloy is longer with ECAP than without, indicating that ECAP process improves the pitting corrosion resistance of anodized Al-Cu alloy. Second phase precipitates such as Si, Al-Cu-Mg and Al-Cu-Si-Fe-Mn intermetallic compounds are present in Al-Cu alloy and the size of these precipitates is greatly decreased by application of ECAP. Al-Cu-Mg intermetallic compounds are dissolved during anodization, whereas the precipitates composed of Si and Al-Cu-Si-Fe-Mn remain in anodic oxide films due to their more noble corrosion potential than Al. FE-SEM and EPMA observation reveal that the pitting corrosion of anodized Al-Cu alloy occurs preferentially around Al-Cu-Si-Fe-Mn intermetallic compounds, since the anodic oxide films are absent at the boundary between the normal oxide films and these impurity precipitates. The improvement of pitting corrosion resistance of anodized Al-Cu alloy processed by ECAP appears to be attributed to a decrease in the size of precipitates, which act as origins of pitting corrosion.

Effect of Pre-Aging on the Microstructure and Strength of Supersaturated AlZnMg Alloys Processed by ECAP

This work is focused on the effect of the combination of natural aging and severe plastic deformation (SPD) produced by Equal-Channel Angular Pressing (ECAP) on the microstructure and strength of supersaturated AlZnMg alloys. Following a solution heat-treatment and quenching into water at room temperature, samples were naturally aged for different time periods and then processed by ECAP. The microstructure and mechanical properties of these samples are described and discussed. This investigation leads to proposing an interesting application of ECAP for supersaturated alloys. Using the shear bands created by ECAP in only one pass and applying appropriate subsequent aging treatments, composite-like microstructures can be achieved in conventional age-hardenanble Al alloys.

強ひずみ加工を施した Al-Cu 合金の陽極酸化膜の耐孔食性

The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L of AlCl3 and also by surface analysis. The time required before initiating pitting corrosion of anodized Al-Cu alloy was longer with ECAP than without, indicating improvement in the pitting corrosion resistance by application of ECAP. Second phase precipitates were present in Al-Cu alloy matrix and the size of these precipitates was greatly decreased by application of ECAP. The precipitates composed of Si and Al-Cu-Si-Fe-Mn were not oxidized during anodization, and the anodic oxide film were absent at the boundary between the normal oxide films and these impurity precipitates. The pitting corrosion of anodized Al-Cu alloy occurred preferentially around these precipitates, the improvement of pitting corrosion resistance of anodized Al-Cu alloy by ECAP appears to be attributable to a decrease in the size of precipitates, which act as origins of pitting corrosion.

Pitting Corrosion Resistance of Anodized Aluminum-Copper Alloy Processed by Severe Plastic Deformation

The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of anodized Al and Al-Mg alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L of AlCl 3 and by surface analysis. The time required for initiating pitting corrosion of anodized Al was longer with ECAP than without, indicating improvement in the pitting corrosion resistance by application of ECAP. However, in anodized Al-Mg alloy, the pitting corrosion occurred earlier with ECAP than without, showing that the corrosion resistance was worse with ECAP than without. SEM and EPMA observation revealed that pitting corrosion of anodized Al occurred around the impurity precipitates and that the size of the impurity precipitates decreased as a result of the ECAP. The improvement in pitting corrosion resistance of anodized Al by ECAP appears to be attributable to a decrease in the size of impurity precipitates. On the other hand, in anodized Al-Mg alloy, cracks occurred in the anodic oxide films during initial corrosion and the cracks were larger with ECAP than without. It is assumed that the pitting corrosion was promoted by the cracks due to the higher internal stress resulting from ECAP.

強ひずみ加工を施したアルミニウム合金の陽極酸化後の耐孔食性

The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L of AlCl3 and also by surface analysis. The time required before initiating pitting corrosion of anodized Al-Cu alloy was longer with ECAP than without, indicating improvement in the pitting corrosion resistance by application of ECAP. Second phase precipitates were present in Al-Cu alloy matrix and the size of these precipitates was greatly decreased by application of ECAP. The precipitates composed of Si and Al-Cu-Si-Fe-Mn were not oxidized during anodization, and the anodic oxide film were absent at the boundary between the normal oxide films and these impurity precipitates. The pitting corrosion of anodized Al-Cu alloy occurred preferentially around these precipitates, the improvement of pitting corrosion resistance of anodized Al-Cu alloy by ECAP appears to be attributable to a decrease in the size of precipitates, which act as origins of pitting corrosion. [doi:10.2320/matertrans.MRA2008216]

Microstructures after Processing by Aging and ECAP for Al-Mg<sub>2</sub>Si Alloys Containing Excess Si or Mg

In this study, severe plastic straining through equal-channel angular pressing (ECAP) is imposed on age-hardenable Al-Mg-Si alloys having two different compositions of excess Si or Mg in the Al-Mg2Si pusedo-binary system. Thereafter, the alloys are subjected to aging and the microstructures are examined using transmission electron microscopy. It is shown that the precipitation behavior is significantly changed through application of ECAP.

Achieving Superplasticity of Al-1%Mg-0.2%Sc Alloy in Plate Samples Processed by Equal-channel Angular Pressing

Equal-channel angular pressing (ECAP) was successfully applied to samples of an Al-1% Mg-0.2% Sc alloy in the form of plates. Pressings were conducted at room temperature using route BCZ in which the plates are rotated in the same direction by 90 � around the vertical axis between each pass. Following ECAP, the grain size was measured as � 0:5 mm. Tensile specimens were cut from the plates and pulled to failure at a temperature of 673 K. Superplastic elongations were achieved and the measured ductilities were essentially independent of the orientation within the plate. These results provide the first demonstration of the potential for directly producing a plate in a superplastic condition through the application of ECAP. Thus, this new procedure removes the necessity of rolling conventional as-pressed bars or rods into sheets or plates for subsequent superplastic forming operations.