Evaluation of (Al)-Si Eutectic Reference Temperature of A3xx Alloys

The modification level of Al-Si alloys is generally evaluated by the depression of the (Al)-Si eutectic temperature which can be recorded by thermal analysis. However, this method requires a reference temperature which should be the eutectic temperature evaluated on the relevant phase diagram. Various methods proposed to account for the effect of low level alloying elements on this reference temperature are reviewed and emphasis is put on the so-called Mondolfo's equation which is updated. Predictions are compared to experimental information from literature

Cooling rate effects on grain size, eutectic modification and Fe-bearing intermetallic precipitation in hypoeutectic Al-Si alloys

Aluminum-silicon alloys are the most common aluminum casting alloys produced due to their fluidity characteristic and mechanical and light weight properties. However, there are several issues concerning application of Al-Si hypoeutectic alloys such as strength, which may be improved by refining grain size of the alloy and modifying silicon precipitates. Furthermore, precipitation of Fe-bearing intermetallics such as the so-called beta phase has a detrimental effect on tensile and ductility properties of Al-Si hypoeutectic alloys. Although various methods have been proposed to mitigate the effect of beta phase, the understanding of the mechanism of growth may be useful to reduce its detrimental effects. The objective of this study is to establish the relationship between the cooling rate and morphology features in Al-Si hypoeutectic alloys. In real casting condition, cooling rate is one of the factors that is not easy to predict, because it is related to the geometry of the parts and to the casting process itself. Changes in cooling rate affect the solidification process, and this is made apparent by the changes in the characteristic temperatures of cooling curves recorded in different locations of a part. The relation between these characteristic temperatures and grain size and eutectic silicon modification are presented. Furthermore, the present study also includes the effect of cooling rate on the morphology of beta phase in the case of a ternary Al-Fe-Si alloy. An attempt to characterize the growth of beta phase was performed through post-mortem and in-situ tomography. In addition, some variations from usual solidification features such as script monoclinic phase and rosettes were observed and are discussed

Characterisation of rosette formation in an aluminium–silicon alloy

Differential thermal analysis has been used to investigate the effect of cooling rate on rosette formation during solidification of a synthetic Al–Fe–Si alloy. Rosettes can be characterised as a very fine multiphase structure within more or less convex areas dispersed in the matrix. Their formation during solidification is related with liquid entrapment and high solidification undercooling associated with the need of independent nucleation events of second phases. It is here shown that their density and internal coarseness depend on cooling rate. Further, metallographic observation of rosettes in contact with large precipitate of b-Al9Fe2Si2 phase allowed to conclude that this latter phase does not help silicon nucleation

Studi Lapisan Intermetalik Cu3sn Pada Ujung Elektroda Dalam Pengelasan Titik Baja Galvanis

Intermetallic Cu3Sn Phase Layer on Electrode’s Tip of Galvanized Resistance Spot Welding. A resistance spotwelding method is commonly used in automotive industries application. In a resistance spot welding method, the copperelectrode has a significant role as an electric current carrier for joining thin metal sheet. This research was focused onstudying the effect of tin layer at the electrode tip for joining galvanized steel sheet. The main variable of this researchis in the thickness of the intermetallic Cu3Sn layer. The result showed that the introduction of tin layer less than 1 μm inthickness on the electrode tip gives a comparable shear strength and nugget diameter distribution with the unplatedelectrode tip

STUDI LAPISAN INTERMETALIK Cu3Sn PADA UJUNG ELEKTRODA DALAM PENGELASAN TITIK BAJA GALVANIS

Intermetallic Cu3Sn Phase Layer on Electrode’s Tip of Galvanized Resistance Spot Welding. A resistance spotwelding method is commonly used in automotive industries application. In a resistance spot welding method, the copperelectrode has a significant role as an electric current carrier for joining thin metal sheet. This research was focused onstudying the effect of tin layer at the electrode tip for joining galvanized steel sheet. The main variable of this researchis in the thickness of the intermetallic Cu3Sn layer. The result showed that the introduction of tin layer less than 1 μm inthickness on the electrode tip gives a comparable shear strength and nugget diameter distribution with the unplatedelectrode tip.Keywords: intermetallic Cu3Sn, shear strength and nugget diameter, spot weldin

Study of the Effect of Cooling Rate on Eutectic Modification in A356 Aluminium Alloys

In this present work, an assessment of eutectic modification based on thermal analysis was performed on modified A356 alloy. The effect of various cooling rates which were achieved by means of casting samples with various moduli in sand and metallic moulds was investigated. Cooling curves recorded from thermocouples inserted in the centre of the samples showed characteristic undercooling and recalescence associated with (Al)-Si eutectic modification. The results showed that cooling rate has a role in observed modification level. Furthermore, differential thermal analysis was included to determine the eutectic melting temperature

Synthesis of TiO2 Nanotube in TI-10Ta-10Nb Thin Film by Anodization

The purpose of this research was to study the synthesis of TiO2 nanotubes on Ti-10Ta-10Nb thin film and the effect of applied potential on the tube size, length and morphology. The Ti-10Ta-10Nb thin film was deposited by dc magnetron sputtering on the CP Ti substrate. The anodization of this Ti-10Ta-10Nb thin film was performed in the solution containing 1M H3PO4 + 1.5wt.% HF at the potential readings of 4, 6, 8 and 10 V for 10 minutes. The results showed that there was a slight increase in the tube diameter from approximately 25 nm at 4 V to 50 nm at 8 V. The length of nanotube varied from 700-900 nm. Interestingly, at the potential of 10 V, the nanotube diameters were damaged with slight decreases in nanotube lengths (500 nm)

Effect of Cooling Rate and Neodymium Addition on Beta Intermetallic Phase of Al–Fe–Si Ternary System

Aluminium silicon alloys are widely used in automotive industry and other structural application. However, the presence of high content of iron element in Al–Si alloys lead to precipitation of beta intermetallic phase that has a detrimental effect on mechanical properties. Reducing the adverse effects of b-Al9Fe2Si2 precipitates can be achieved by altering their morphology by adding element modifier and increasing solidification cooling rate. In this present work, simultaneous thermal analysis was used to study the effect of cooling rate (5, 10 and 30°C min-1) on beta phase formation in Al–7Si–1Fe alloy added with neodymium at 0.3, 0.6 and 1 wt%. The beta phase precipitates were then characterized using optical microscopy and scanning electron microscopy equipped with EDS. Image analysis results showed the reduction in size of beta intermetallic phase as a result of the rare earth addition. Further analysis also showed the refinement of eutectic silicon

Solidification sequence and four-phase eutectic in AlSi6Cu4Fe2 alloy

International audienceDifferential thermal analyses of an AlSi6Cu4Fe2 alloy at various cooling rates from the liquidstate were performed which showed: i) possible discrepancies in the first solidification stepsand; ii) solidification ending with multiple peaks at low cooling rate. Metallographicobservation of the samples gave hint for understanding the discrepancies while the presenceof rounded multi-phase pools – or so-called rosettes - entrapped within dendrite armsexplained the multiple peaks because they solidified independently of each other.The very fine eutectic microstructure in these rosettes was investigated by scanning electronmicroscopy which showed the precipitation of a four-phase eutectic. Focused ions beammilling was then used to investigate the topology of the distribution of the four phases.Electron backscattered diffraction analysis was carried out to investigate their localcrystallographic orientations and transmission electron microscopy analysis was performed toidentify the very fine crystalline structures. This eutectic appears as one of the very fewregular four-phase eutectics reported in the literature