A model for equiaxed grain formation along the weld metal fusion line

Cross, C. E.; Grong, Ø.; Mousavi, M. G.

doi:10.1016/s1359-6462(99)00023-8

Cited by 28 publications

(23 citation statements)

References 8 publications

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“…Cross et al also observed and reported an oriented dendritic growth of grains in the weld metal due to the differential heat flux. 25 The distributions of eutectics ( Fig. 7) in both the passes were very coarse and continuous along the grain boundary.…”

Section: Single Pass Weldsmentioning

confidence: 90%

Improvement of mechanical properties of aluminium–copper alloy (AA2219) GTA welds by Sc addition

Seshagiri¹,

Nair²,

Reddy³

et al. 2008

Science and Technology of Welding and Joining

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Aluminium alloy AA2219 is a high strength alloy widely used for aerospace application. One of the drawbacks of most of the high strength aluminium alloys is that they suffer from poor weldability. However, AA2219 is an exception due to the presence of more copper that helps in healing cracks by providing extra eutectics. Although AA2219 has excellent weldability, the strength of a welded joint is only 35-45% of the base metal. The loss of strength is due to the dissolution of the strengthening precipitates during melting. Therefore, there is a need to improve the fusion zone strength of AA2219 welds. In this study, an attempt was made experimentally to use different gas tungsten arc welding (GTAW) techniques and modify the filler chemistry with addition of scandium (Sc) and zirconium (Zr) in order to improve the mechanical properties of the AA2219 weld joints. The application of the GTAW DCEN with Sc and Zr to the filler wire proved to be the most economical and perhaps the optimal choice for welding AA2219 aluminium alloys. Addition of Sc and Zr to the fusion zone during welding enhanced grain refinement in the GTAW welds leading to better mechanical properties when compared to welding with conventional AA2319 filler.

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Section: Single Pass Weldsmentioning

confidence: 90%

Improvement of mechanical properties of aluminium–copper alloy (AA2219) GTA welds by Sc addition

Seshagiri¹,

Nair²,

Reddy³

et al. 2008

Science and Technology of Welding and Joining

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“…Most of these articles came from the field of welding [2,3,4] but there are some references to the production of steel with 100 pct equiaxed structure in Posco [5] and Sumitomo. [6] There are also some interesting insights into the mechanisms of heterogeneous nucleation from the external inoculation process that has been long used in the production of aluminum.…”

Section: Introductionmentioning

confidence: 99%

“…From the analysis of weld pool solidification, it is well reported that the amount of equiaxed zone depends on the type of inclusions or inoculant particles and that the lattice disregistry between inclusions and solid metal may define undercooling. [2,3,4] In Al-alloy casting, [7,8] a fine, uniform, and equiaxed microstructure can be achieved by inoculation, but because the inoculants are potent and the nucleation undercooling is very low, the classical spherical-cap model is not useful in explaining the results. Alternative models have shown that the adsorption of solutes in the substrate/melt interface as well as the reaction between the substrates and the melt can have effects on solidification that are not expected from the classical nucleation theory.…”

Section: Introductionmentioning

confidence: 99%

Controlled undercooling of liquid iron in contact with Al2O3 substrates under varying oxygen partial pressures

Valdez

Uranga

Fuchigami

et al. 2006

Metall Mater Trans B

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The objective of this study was to determine the conditions under which alumina can act as a heterogeneous nucleant to initiate the solidification of undercooled liquid iron. The undercooling of a pure iron sessile droplet in contact with Al 2 O 3 substrates was measured under controlled oxygen partial pressures by observing droplet recalescence. The experimental results indicated that the undercooling of liquid iron, in contact with an Al 2 O 3 substrate, did not have a unique value, varied from 0°C to 290°C, and was significantly affected by the oxygen content of the gas phase and the degree of interaction between the oxide and the metal. Deep undercoolings are possible at low oxygen potentials, provided the oxygen potential is such that substantial substrate decomposition does not occur. The measured undercooling was a strong function of gas phase oxygen content and a maximum in undercooling of 290°C was measured at PO 2 5 10 À19 atm. The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deepest undercoolings occurred when the highest contact angle between the substrate and the liquid droplet was achieved.

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“…This suggestion is based on heterogeneous nucleation in a stagnant liquid region called the unmixed zone (UMZ). Three possible factors: (i) welding conditions, (ii) composition, and (iii) base metal microstructure have been considered in an effort to better understand the EQZ formation (Cross et al, 1999;Reddy et al, 1998c). Based on the observations, a unified heterogeneous nucleation mechanism has been proposed that accounts for the effects of Li and Zr on the formation of EQZs:…”

Section: Hypotheses Of Eqz Formation and Their Evaluationmentioning

confidence: 99%