Experimental investigation of the hot cracking mechanism in welds on the microscopic scale

Abstract

The results of the accurate experimental observations on binary Al-Si alloys are presented, which clearly demonstrate that the solidification cracking is a result of the accumulation of macroscopic tensile displacement in aβmicroscopic intergranular liquid film of segregates at the final stage of the weld metal solidification. The reconstructed mechanism of crack initiation provides a clear phenomenological interrelation between the cracking susceptibility, parameters of the welding process and properties of the base and filler material. The correspondent numerical model takes into account the effects of displacement accumulation as well as the influence of thermo-dynamical and thermo-mechanical properties of the welded material. It is successfully applied for development of technological means for elimination of the solidification cracking during welding of aluminium alloys AA6056, such as a multi-beam welding.

Keywords

welding / solidification cracking / numerical simulation

References

[1] Singer A R E, Jennings P H. Hot-shortness of the aluminium-silicon alloys of commercial purity. Journal of the Institute of Metals , 1946, 73: 197–212
[2] Singer A R E, Jennings P H. Hot-shortness of some aluminium-iron-silicon alloys of high purity. Journal of the Institute of Metals , 1947, 73: 273–284
[3] Jennings P H, Singer A R E, Pumphrey W I. Hot-shortness of some high-purity alloys in the systems aluminium-copper-silicon and aluminium-magnesium-silicon. Journal of the Institute of Metals , 1948, 74: 227–248
[4] Pumphrey W I, Lyons J V. Cracking during the casting and welding of the more common binary aluminium alloys. Journal of the Institute of Metals , 1948, 74: 439–455
[5] Prokhorov N N. Hot Cracking During Welding. Moscow: Mashgiz, 1952 (in Russian)
[6] Bochvar A A, Rykalin N N, Prokhorov N N, . The question of “hot” (crystallisation) cracks. Welding Production , 1960, 10: 5–7 (in Russian)
[7] Prokhorov N N. The technological strength of metals while crystallizing during welding. Welding Production , 1962, 9(4): 1–8 (in Russian)
[8] Jonsson M, Karlsson L, Lindgren L E. Thermal stresses, plate motion and hot cracking in butt-welding. Mechanical Behaviour of Materials IV . New York: Pergamon Press, 1984, 273–279
[9] Dike J J, Brooks J A, Li M. Comparison of failure criteria in weld solidification cracking simulations. In: Cerjak H, ed. Mathematical Modelling of Weld Phenomena 4 . London: IOM Communications Ltd., 1998, 199–222
[10] Feng Z. A computational analysis of thermal and mechanical conditions for weld metal solidification cracking. Welding in the World , 1994, 33(5): 340–347
[11] Zaharia T. Dynamic stresses in weld metal hot cracking. Welding Journal , 1994, 73(7): 164s–172s
[12] Dike J J, Brooks J A, Krafcik J S. Finite element modelling and verification of thermal-mechanical behaviour in the weld pool region. In: Smartt H B, Johnson J A, David S A, eds. Trends in Welding Research. ASM International , 1996, 159–164
[13] Feng Z, Zaharia T, David S A. On the thermomechanical conditions for weld metal solidification cracking. In: Cerjak H, ed. Mathematical Modelling of Weld Phenomena 3 , 1996, 114–147
[14] Feng Z, Zaharia T, David S A. Thermal stress development in a nickel based superalloy during weldability test. Welding Journal , 1997, 76(11): 470–483
[15] Makhnenko V I, Velikoivanenko E A, Rozynka G F, . A computer program for prediction the zones with the risk of formation of hot cracks in welding with deep penetration. The Paton Welding Journal , 1998, 10(2): 57–65
[16] Weise S. Hei?ri?bildung beim Laserstrahlschwei?en von Baust?hlen. Bremen: BIAS-Verlag, 1998 (in German)
[17] Herold H, Streitenberger M, Pchennikov A. Modelling of the PRV-test to examine the origin of different hot cracking types. In: Cerjak H, ed. Mathematical Modelling of Weld Phenomena 5 . London: IOM Communications Ltd., 2001, 783–792
[18] Shibahara M, Serizawa H, Murakawa H. Finite element method for hot cracking analysis under welding using temperature dependent interface element. In: Sahm P R, ., eds. Modelling of Casting, Welding and Advanced Solidification Processes IX. Aachen: Shaker-Verlag , 2000, 844–851
[19] Shibahara M, Serizawa H, Murakawa H. Finite element method for hot cracking analysis using temperature dependent interface element. In: Cerjak H, ed. Mathematical Modelling of Weld Phenomena 5 . London: IOM Communications Ltd., 2001, 253–267
[20] Bergmann H W, Hilbinger R M. Numerical simulation of centre line hot cracks in laser beam welding of aluminium close to the sheet edge. In: Cerjak H, ed. Mathematical Modelling of Weld Phenomena 4 . London: IOM Communications Ltd., 1998, 658–668
[21] Hilbinger R M, Bergmann H W, K?hler W, . Considering of dynamic mechanical boundary conditions in the characterisation of a hot cracking test by means of numerical simulation. In: Cerjak H, ed. Mathematical Modelling of Weld Phenomena 5. London: IOM Communications Ltd., 2001, 847–862
[22] Hilbinger R M. Hei?rissbildung beim Schwei?en von Aluminium in Blechrandlage, Universitaet Bayreuth, Bayreuth, 2000 (in German)
[23] Pellini W S. Strain theory of hot tearing. Foundry , 1952, 80: 125–199
[24] Plochikhine V, Prikhodovsky A, Zoch H-W. Zum Mechanismus der Hei?rissbildung beim Schwei?en von Al-Legierungen. H?rterei-Technische Mitteilungen , 2003, 58(6): 357–362 (in German)
[25] Ploshikhin V, Prikhodovsky A, Ilin A, . Mechanical-Metallurgical approach for prediction of solidification cracking in welds. In: Cerjak H, ed. Mathematical Modelling of Weld Phenomena 8 . London: IOM Communications Ltd., 87–104
[26] Saunders N, Miodownik A P. CALPHAD (Calculation of Phase Diagrams): A Comprehensive Guide (Pergamon Materials) Series Vol. 1. Elsevier Science , 1998
[27] Andersson J-O, Helander T, H?glund L, . Thermo-Calc & DICTRA, computational tools for materials science. Calphad , 2002, 26(2): 273–312 10.1016/S0364-5916(02)00037-8
[28] Saunders N. The application of calculated phase equilibria to multi-component aluminium alloys. Journal of Japanese Institute of Light Metals , 2001, 51: 141–150
[29] Akesson B, Karlsson L. Prevention of hot cracking of butt welds in steel panels by controlled additional heating of the panels. Welding Research International , 1976, 6(5): 35–52
[30] Shumilin V G, Karkhin V A, Rakhman M I, . A technique of arc welding. USSR Patent, No. 1109280, 1980
[31] Herold H, Streitenberger M, Pchennikov A, . Modelling of one sided welding to describe hot cracking at the end of longer butt weld seams. Welding in the World , 1999, 43(2): 56–64