Weld metal composition change during conduction mode laser welding of aluminum alloy 5182

Abstract

Selective vaporization of volatile elements during laser welding of automotive aluminum alloys affects weld metal composition and properties. An experimental and theoretical study was carried out to seek a quantitative understanding of the influences of various welding variables on vaporization and composition change during conduction mode laser welding of aluminum alloy 5182. A comprehensive model for the calculation of vaporization rate and weld metal composition change was developed based on the principles of transport phenomena, kinetics, and thermodynamics. The calculations showed that the vaporization was concentrated in a small high-temperature region under the laser beam where the local vapor pressure exceeded the ambient pressure. The convective vapor flux driven by the pressure gradient was much higher than the diffusive vapor flux driven by the concentration gradient. The computed weld pool geometry, vaporization rates, and composition changes for different welding conditions agreed well with the corresponding experimental data. The good agreement demonstrates that the comprehensive model can serve as a basis for the quantitative understanding of the influences of various welding variables on the heat transfer, fluid flow, and vaporization occurring during conduction mode laser welding of automotive aluminum alloys.

Effects of Different Shielding Gases and Power Waveforms on Penetration Characteristics and Porosity Formation in Laser Welding of Inconel 690 Alloy

“…14,30,31) The content of the trapped bubbles depends on the nature of the shielding gas (e.g. the type of shielding gas), 14,18) the shielding conditions, 16,[32][33][34] the vapour pressure of the metal, 35,36) the viscosity of the molten metal 21) and the dynamics of the keyhole during the welding process. 10,37) The floatability of the bubbles is affected by the characteristics of the output power (e.g.…”

“…the power waveform), 38) the surface tension of the molten pool, 8) and the direction of the molten metal flow (Marangoni flow). 35,39,40) Therefore, the content of the weld porosity depends on the factors which trap the bubbles and enhance the bubble floatability.…”

Estimation of Composition Change in Pulsed Nd:YAG Laser Welding

“…Substituting equations (1) and (4) in to equation (3) ,the evaporation velocity of the ith point on the keyhole surface is given by:…”

“…To realize a quantitative estimation of the weld metal composition, while varying the irradiation parameters, a comprehensive model is required. Several authors have used Longmuir equation for the calculation of the changes in weld metal composition due to various welding processes [1,2].The equation is useful for calculation of relative vaporization rates from different alloying elements in vacuum and it results to a higher absolute rate than actual values [2][3][4][5]. Mundra and T.Debroy [2] derived equations for the vaporization rate of various alloying elements in conduction mode laser welding of high-manganese stainless steel with a CW 2 CO laser.…”

Heat and mass transfer in laser dissimilar welding of stainless steel and nickel

“…Marangoni-Benard convection due to temperature gradient on the surface of the molten pool and Rayleigh-Benard convection due to variation of density inside the molten pool were numerically studied and compared [7,8], under the presence or absence of surface active element such as sulfur [9][10][11] and oxygen [12][13][14]. Heat and mass losses due to vaporization of elements in conduction mode laser welding of alloys were investigated using various models [15][16][17][18]. Nonequilibrium solidification nature and solute partitioning at the solid-liquid interface in laser processing were also accounted for [19,20].…”