Papers by Keyword: Pure Aluminium

Abstract: In this study, the relationship between the structure and properties of commercial purityaluminium (AW-1199) was investigated by applying constrained groove pressing (CGP) method.The refinement of the coarse grain aluminium microstructure to submicrocrystalline size by largeplastic strain at room temperature defined. The impact of various strains upon microstructurechanges is investigated using transmission electron microscopy (TEM) and electron back scatterdiffraction (EBSD). A mixture of subgrains produced by grains subdivision and polygonizedsubgrains formed locally due to dynamic recovery was found in the deformed aluminium. Thetensile properties and resulting hardness are related to microstructural evolution induced by CGP. Asubstantial impact of straining upon the increasing in tensile strength was observed after the firstpass. Further strain increase had an insignificant effect on tensile strength but was accompanied byductility loss. The post deformation annealing effect was then explored with aim to increase theductility. The results indicate that changes in strength and ductility may be related to formation of abimodal structure.

Abstract: Growth restriction plays an important role in grain refinement and is often linked with as-cast grain size of Al-Alloys. It has been suggested that Ti is the most powerful solute element for growth restriction among all the commonly used alloying elements. In this work, the growth restriction effect of Ti on the grain refinement of high purity Al (HP-Al, 99.99%) and commercial purity Al (CP-Al, 99.7%) has been investigated using the Alcan TP-1 tests. Grain refining tests were conducted with the same inoculation of potent TiB₂ at a fixed level and free Titanium addition. The results showed that, when the TiB₂ inoculation was fixed to be equivalent to the particle number density of 0.2% Al-5Ti-1B addition, CP-Al has a fully equiaxed grain structure with only 46 ppm solute Ti, while HP-Al has a fully equiaxed grain structure with much higher Ti addition (960 ppm).

Abstract: In this paper, samples were prepared by power ultrasonic on molten Al ingot. The results show that microstructure of the samples treated by untrosonic vibration is more finer than that of the untreated ones, the ultrasonic treatment time is not the longer the better. When the vibration head dipped into the middle of the melton, the better grain refinement effect can be gotten. Too deep or too shallow of the vibration head dipped in, vibration effect just limited to near the head, the influence is relatively small when the melton far away from the vibration head.

Abstract: The study presented in this paper is focused on the effect of surfaces roughness of pure aluminium A1100 on the cold work extrusion process by three different angles of taper die. Different angles of taper die will affect the surface roughness of the workpiece. To protect the surface and to reduce friction, lubricants are often used in extrusion process [1]. Different lubricants may have different optimum taper die angle that are suitable to be applied. Two types of materials used in this experiment are steel SKD 11 for taper die and aluminium A1100 for workpiece and different angles applied are 30^o, 45^o, and 60^o. Moreover, with respect to each angle, three different types of lubricants were used which are Daphne Draw S Series, Palm Olein, and EFB bio oil. The Universal Testing Machine and Surface Roughness Tester were used in this experiment. The result obtained from the experiment shows that at 30^o of taper die angle were producing the smooth product surfaces for each lubricant and Daphne Draw S Series could reduce the surface roughness compared to other lubricant test.

Abstract: The creep deformation in pure aluminum was investigated using helicoid spring samples at room temperature, 298 K, and σ < 1.19 MPa. It was found that the stress exponent is n = 0, which means the creep behavior in this region is independent on applied stress but some physical properties of materials. The creep behavior was suggested to be controlled by surface diffusion based on the strongly effect of surface area on creep behavior only in this creep region (n = 0). The threshold creep rate, , called intrinsic deformation limit, decided by surface diffusion was suggested. This discovery provided a new perspective to understand the extremely slow deformation in the nature.

Abstract: The effect of DC and AC magnetic fields on the macrostructure, morphology and distribution of the iron-containing intermetallics in the commercially pure Al was investigated. It is found that, at a cooling rate of 3°C/min, the grain is very coarse when the alloy solidifies both with and without magnetic fields. Comparing with the sample solidifies without magnetic field, the solidification structure has almost no change when it solidifies under DC magnetic field, while AC magnetic field changes the solidification structure obviously and makes grains show radial columnar crystals. The intermetallics is dominated by long needle-like phase when the sample solidifies under the condition of no magnetic field. Under AC magnetic field, the intermetallics is refined and accumulated towards the center of sample, and the amount of bone-like α-AlFeSi phase is increased remarkably. The mechanism of the effect of magnetic fields was discussed.

Abstract: The current study deals with the main features of heath treated aluminium alloy EN-AW 1050A H24 to be used for structural applications. This is an almost pure aluminium whose employment is innovative in the civil engineering field and that, for this reason, needs to be carefully investigated in relation to its performance. On this prospective the main results of a wide experimental campaign, carried out on specimens subjected to static or dynamic loadings, as well as to monotonic or cyclic strains, are shown. In addition, some remarks about the residual stresses induced by welding processes are given. Finally, analytical or numerical models obtained by the above tests are provided.

Abstract: The voids in pure Aluminum always exit in the manufacturing process. The Modified Embedded Atom Method (MEAM) potential is employed in the molecular dynamics (MD) simulation at atomic scale to investigate the interaction between voids under the impact loading for pure Aluminum. The distance between the voids distributed along the loading orientation affects the failure mechanism seriously. The results show that there are 3 kinds of mechanisms with the change of the distance between voids: 1) coalescence takes place within a critical distance between voids under extra loading, 2) when the distance between voids reaches a certain value, each void cracks at 4 locations along with the slide direction <110> of face-centered cubic (fcc), respectively, 3) a stress shield zone appears when the ligament between the voids is at the size between the cases mentioned above, which brings out the phenomena that each of the voids cracks only at 2 locations, and no crack appeared at the stress shield zone.

Abstract: Mechanically milled pure aluminium powders were fabricated into bulk materials using back pressure equal channel angular consolidation (BP-ECAC) for four or eight passes at 373K. The bulk materials consolidated from 0 h and 4 h mechanically milled powders were characterised by Vickers hardness tests and density measurements. Thermal stability of the consolidated bulk materials was evaluated by isothermal heat treatments at 673K. The as-consolidated bulk material from the 0 h milled (i.e. unmilled) powder showed nearly full density. However, full density was not obtained with the 4 h milled powder even after eight passes. The HV values for the as-consolidated materials fabricated from the 0 h and 4 h milled powders after four passes and from the 4 h milled powder after eight passes were 57, 121 and 136, respectively. Softening was observed in the bulk material consolidated from the 0 h milled powder during the isothermal heat treatment. However, the hardness of the bulk materials consolidated from the 4 h milled powders after four and eight passes increased to maximum values of 137 and 141 after heat treatment for 28 h and 8 h at 673K, respectively. The maximum hardness was maintained for up to 100 h at 673K in both materials. The hardening and thermal stability in the bulk materials from the milled powders are attributable to dispersion strengthening of Al4C3 particles formed by solid-state reaction during the isothermal heat treatment.

Abstract: The present study tried to control grain structure in polycrystalline aluminum or titanium by means of a laser spot heating method as well as by a computer simulation technique. Monte Carlo simulation of spot heating was performed utilizing two-dimensional grain structure model composed of 200 x 200 sites with hexagonal cells. Grain growth proceeded preferentially in the higher temperature region and resulted in a large grain surrounded by small grains. This large grain tended to keep on growing during homogeneous heating after the spot heating, suggesting that the spot heating technique can fabricate a peculiar grain structure such as different grain size distribution and texture that are not realized by utilizing conventional uniform heating process. Laser spot heating utilizing a fiber-laser system realized heating of small area such as 30micorn diameter to bring about peculiar grain size distribution as calculated by the computer simulation.