Aluminium Magnesium Silicon Alloy Research Articles

Effects of processing temperature on failure mechanisms of dissimilar aluminum-to-polymer joints produced by friction stir welding

An engineering grade, glass fibre reinforced (GFR) polymer – Noryl™ Resin GFN2 - and an aluminum magnesium silicon alloy - AA6082-T6 - were joined by Friction Stir Welding (FSW) in overlap configuration. A systematic analysis was conducted on the effects of different process parameters, namely, vertical force, rotating speed and transverse speed, on processing temperature and mechanical performance, and how they relate with the failure mechanisms of the joints. The analysis encompassed the morphology of the joints’ interfaces and generated defects associated to the joining process. The quasi-static tensile tests resulted in average tensile strengths varying between 15.9 and 37.9 MPa, representing joints’ efficiencies ranging from 19.9% up to 47.4%. Both macro and micromechanical interlocking were found to be the main joining mechanisms, whilst chemical bonding played a secondary role. The development of interlocking features was found to be related with the processing temperature, and it should be comprised between the softening and melting temperature of the polymeric material. Processing temperature influences both the joints’ strength, and failure mechanisms, with low strength joints’ tending to exhibit interfacial failure, whereas high strength joints’ failure can be associated with the failure of the weakest base material close to the joint region. This research work validates the feasibility of dissimilar polymer-to-metal joining through FSW. To this end it was studied the failure mechanisms in the Aluminum and the GFR polymer which exhibit highly dissimilar physical and thermo-mechanical properties. The mechanical performance of these joints is limited by the weakest base material and is mainly governed by macro and micro-mechanical interlocking features, which relates to the failure mechanism. The relation between macro and micro-mechanical interlocking features, failure mechanism and joint strength is crucial towards maximization of the joints’ mechanical performance.

Uncharacteristic evolution of copper type texture in the presence of shearable precipitates

Abstract In the present work, development of rolling texture in the presence of shearable precipitates is analyzed using age hardenable aluminum magnesium silicon alloy (AA 6061) and aluminum-copper-lithium alloy (AA 2195). A characteristic Brass type texture evolves upon rolling of AA 6061 alloy containing β’’ (Mg5Si6) precipitates, whereas an unexpected Copper type texture develops upon rolling of AA 2195 alloy containing T1 (Al2CuLi) precipitates. The present work highlights that rolling texture evolution in the presence of shearable precipitates cannot be generalized and depends strongly upon the shearing propensity of these precipitates.

Stress relaxation behavior of an aluminium magnesium silicon alloy in different temper condition

In the present investigation, stress relaxation tests were carried out on an aluminium magnesium silicon alloy to determine rate controlling mechanism in different temper conditions. Single and multiple relaxation tests were carried out to determine apparent and physical activation volume. It was found that in the presence of solutes and incoherent precipitates, dislocation-dislocation interaction is the rate controlling mechanism, whereas dislocation-precipitate interaction is the rate controlling mechanism in the presence of semi-coherent precipitates. Moreover, the nature of deformation was found to be more viscous (higher strain rate sensitivity) in the presence of semi-coherent precipitates compared to other microstructural features (solutes, incoherent precipitates). Special emphasis is placed upon understanding exhaustion rate of mobile dislocation density during relaxation period. It was found that the exhaustion rate of mobile dislocation density is negligible in the presence of incoherent precipitates, whereas a significant reduction in mobile dislocation density was observed in the presence of solutes and semi-coherent precipitates. Furthermore, thermal and athermal components of the flow stress were determined to develop a comprehensive understanding regarding deformation behavior in different temper conditions.

Effect of Heat Treatment on Proportion of Duplex Fiber Texture of Aluminium Magnesium Silicon Alloy

In the present study an attempt has been made to understand the texture evolution of Aluminium alloy T after different aging heat treatment process Effects of heat treatment in controlling the variation and domination of one fiber texture over the other in a duplex fiber texture have been observed Texture studies were carried out with ND direction parallel to direction of extrusion Solutionised and aged samples have shown the variations in volume fraction of lt gt and lt gt fibre due to effect of re crystallization and precipitation The presence of clusters of solutes and beta prime prime precipitates alters the proportion of volume fraction of lt gt and lt gt duplex fibers Peak aged samples showed significant strengthening of lt gt fiber as compared to solutionised and aged samples

Effect of the interfacial reaction of aluminum and yttrium oxide on aging behavior of aluminum–magnesium–silicon alloy reinforced with yttrium oxide modified sub-micron alumina

Age-strengthening behavior of Al–Mg–Si alloy composites reinforced with sub-micron alumina particles modified by yttrium oxide under the temperature of 130°C, 160°C and 190°C was investigated. The mechanical performances of unmodified and modified composites after the aging treatment were evaluated with the tensile test. The results indicate that the hardness level of modified composites is obviously increased compared to unmodified composites at different aging states, and the process of aging precipitation of the matrix alloy in modified composites is accelerated by the interfacial reaction of aluminum and yttrium oxide. The aging microstructures of modified composites have a significant difference compared to non-modified composites, and present a large amount of dislocations and precipitates in the matrix alloy. The modified composites treated by the aging exhibit excellent tensile properties. It is suggested that the interfacial reaction resulted from the surface modification of particles with the rare-earth yttrium oxide is beneficial in promoting the process of aging precipitates and strengthening the aging microstructures and properties of Al alloy matrix in modified composites.

Effect of crystallographic texture on precipitation induced anisotropy in an aluminium magnesium silicon alloy

Abstract The effect of crystallographic texture on precipitation induced anisotropy in yield strength of an aluminium magnesium silicon alloy was investigated. Solutionized samples were subjected to unidirectional and multi-step cross rolling to yield distinct crystallographic textures in the Al–Mg–Si alloy. The rolled sheets were then subjected to annealing followed by second solutionizing treatment to provide sheets with similar grain size and dislocation content but distinct texture. Ageing experiments were carried out on these sheets at 443 K for different time intervals. It was observed that the evolution of anisotropy in yield strength of the age hardened alloy depends on texture. The difference in age hardening response brought about by varying initial texture controls the evolution of anisotropy in mechanical properties of the alloy. This was manifested in terms of transition from anisotropic to isotropic mechanical properties in the unidirectionally rolled samples after peak ageing. On the contrary, a transition from isotropic to anisotropic yield behaviour was observed for multi-step cross rolled samples. This is attributed to enhanced precipitation hardening in crystallographically softer orientations compared to crystallographically harder orientations.

Aging behavior of the matrix of aluminum–magnesium–silicon alloy including carbon nanotubes

The mechanical behavior of the non-aged and the aged Al–Mg–Si alloy composites reinforced with CNTs was evaluated with tensile test and Vickers hardness test. The composites showed higher mechanical strength than the pristine Al alloy before the aging, although exhibiting lower mechanical strength after the aging. The aging treatment was ineffective to strengthen the Al–Mg–Si alloy composites reinforced with CNTs. EDS elemental mapping clarified the Mg and O concentration around CNTs. The reduction of Al oxide species formed around CNTs facilitated the Mg concentration. Due to the Mg consumption around CNTs, Mg elements in Al matrix decreased, and resulted in the incomplete matrix strengthening after the aging.

High cycle fatigue behaviour of microsphere Al 2O 3–Al particulate metal matrix composites

The high-cycle stress-life ( S– N) curve and fatigue crack growth threshold (Δ K th) behaviour of COMRAL-85 TM, a 6061 aluminium–magnesium–silicon alloy reinforced with 20 vol.% Al 2O 3-based polycrystalline ceramic microspheres, and manufactured by a liquid metallurgy route, have been investigated for a stress ratio of R = −1 (fully reversed loading). Fatigue testing was conducted on both smooth round bar ( S– N) specimens and notched round bar (fatigue threshold) specimens. Unreinforced Al 6061-T6 also processed by a liquid metallurgy route and six powder metallurgy processed composites with particle volume fractions ranging between 5% and 30% were also studied. S– N data revealed that the powder metallurgy processed composites generally gave longer fatigue lives than the matrix alloy, whereas COMRAL-85 TM exhibited a reduced fatigue life. The fatigue threshold results were very similar for all the composites, being lower than for Al 6061-T6. Fatigue failure mechanisms were determined from examination of the fracture surfaces and the crack profiles.

Fracture toughness of microsphere Al 2O 3–Al particulate metal matrix composites

The fracture toughness and behaviour of COMRAL-85 TM, a 6061 aluminium–magnesium–silicon alloy reinforced with 20 vol% Al 2O 3-based polycrystalline ceramic microspheres, and manufactured by a liquid metallurgy route, have been investigated. Fracture toughness tests were performed using short rod and short bar (chevron-notch) specimens machined from extruded 19 mm diameter rod, heat treated to the T6 condition. The fracture toughness in the R–L orientation was found to be lower than in the C–R or L–R orientations owing to the presence of particle-free bands in the extrusion direction. Short rod tests were also conducted for the R–L orientation on six powder metallurgy composites with particle volume fractions ranging between 5% and 30%. It was found that the fracture toughness decreased progressively with particle volume fraction, but at a decreasing rate. A detailed examination of the fracture behaviour was made for both the liquid metallurgy and powder metallurgy processed composites.

Surface reactions during pickling of an aluminium–magnesium–silicon alloy in phosphoric acid

The surface products formed during pickling of a modified AA 6000 alloy (0.70Mg1.52Si) in 0.1 M phosphoric acid were analysed using electron spectroscopy for chemical analysis, Auger electron spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. Cold-rolled and heat-treated samples were compared. Pure Si, Mg 2Si and AlFeSi particles are present in the material after the heat treatment. Pickling gives a chemical dissolution of the surface oxide and an anodic dissolution of the Mg 2Si particles. The degree of dissolution increases with the pickling time. On the cathodic AlFeSi particles, aluminium phosphate is deposited. After prolonged pickling, micropits are visible on the surface. It is suggested that this is due to the dissolution of small Mg 2Si particles precipitated during the annealing process.

An investigation of fusion zone microstructures of welded aluminum alloy joints

Fillet weld “T” joints were produced using dissimilar aluminum alloys by a manual arc welding process. In this study, a heat treatable aluminum–magnesium–silicon alloy and a non-heat treatable aluminum–magnesium alloy were joined. The microstructure of the fusion zone was characterized by optical microscopy. Results reveal that the manual welding process produces adequate fusion, while minimizing weld structure defects.

Performance in Atmospheric Exposure of an Aluminium Alloy Anodised by the Sulphuric Acid Process for Architectural Use: Report prepared on behalf of the former C.I.D.A. Working Panel for Atmospheric Exposure Testing

Specimens of aluminium magnesium silicon alloy to the HE 9 designation of BS 1476 were anodised to two anodic film thicknesses and sealed using four different processes; two methods of surface pretreatment of the metal were used prior to anodising. All the HE 9 material was derived from a single source but specimens were processed by each of the participating member countries in sufficient quantity to allow triplicate exposures to be mounted at five exposure sites throughout Europe. The five sites covered a range of atmospheric conditions and the use of triplicate exposure specimens enabled variations to be made in the degree of maintenance applied to individual replicate groups at each site.Exposure of the specimens began in the Spring of 1965, and they have shown little deterioration during the six years exposure period covered by this report. The present paper illustrates the excellent performance obtained and comments on the small effect on performance which has so far resulted from the variations in processing included in the test programme.

The thermo-mechanical behavior of 6061 aluminiummagnesiumsilicon alloy

The strength of age hardening aluminummagnesiumsilicon alloy 6061 has been analyzed in terms of thermally activated dislocation motion. Petinent models for the athermal component of the flow stress were modified for application to the needle-shaped GP zones in this alloy because existing treatments have been developed and evaluated only for spherical or disk-shaped zones. The results of that step were combined with an equation for the kinetics of aging to produce a relation which could be compared with experiment. Results indicate that the athermal flow stress is controlled primarily by the work required for dislocations to shear through the GP zones. It is shown that the thermal component of the flow stress cannot be adequately explained either by long range elastic stresses at the zones, or by the mechanism of jog formation at intersecting dislocations. Instead, the shear of GP zones contributes significantly to the thermally activated flow stress. The measured thermal stress component is compared with the predictions of a model which is physically consistent with the mechanism for the athermal stress, and the contributions of compatibility slip and dislocation bowing are taken into account.

Anodizing in Aqueous Solutions of Organic Carboxylic Acids

SummaryUsing HE9 material (an aluminium—magnesium silicon alloy) the anodic reactions of a number of water-soluble organic caboxylic acids not generally described in the literature are summarized, with and without small additions of oxalic acid. The electrolytic processes are related to the strength (conductivity and acidic dissociation constants) of the acid electrolytes, both singly and in combination with oxalic acid, together with the general chemical properties of the ionic species involved. The reason for the production of integrally coloured coatings using some of the electrolytes is discussed and the properties of some of the thicker films obtained summarized.