Microstructure And Mechanical Property Evolution Of5A30Aluminum Alloy During Friction Stir Welding

5A30aluminum alloy is designed by China independently, it is a new type ofaluminum alloy which is developed on the basis of5083aluminum alloy. Friction stirwelding is recognized as a promising solid connection technology, both in China andabroad. Currently, research onfriction stir welding of5A30aluminum alloy is rarereported. Therefore, this paper selected5A30aluminum alloy plate as the researchobject and usedSEM-EBSD to study the evolution of microstructure of the variousregions after friction stir welding.The form of material flow and the mechanism ofdynamic recrystallization were also discussed. Havingstudiedthe distribution of secondphase and mechanical property by using SEM-ECC. The main results including:①Through the studying of EBSD, we knowwelding joint include base material(BM), heat affected zone (HAZ), the mechanical affected zone (TMAZ) and nuggetzone (NZ). Dynamic recrystallization occurred in NZ and the microstructure variedfrom elongated grains to equiaxed grains.Average grain size became smaller graduallyfrom top to bottom.Thedynamic recrystallization mechanism werecontinuous dynamicrecrystallization (CDRX) and geometric dynamic recrystallization (GDRX);TMAZgrains were elongated grains mixed with recrystallized grains; HAZ only experiencedcycle heat, grains in this zone were the same with BM.②The form of the material flow wasobtained by EBSD study ofTMAZ duringfriction stir welding. Inshoulder affected zone,material rotated clockwise with theshoulder and moved forward on the advancing side (AS),material rotated clockwisewiththe shoulder and moved backwards on the retreating side (RS); Inpin affected zone,material rotated clockwise with the pin firstly, and then moved backwards to fill thecavity which is left by the moving forwards pin on the AS,material rotated clockwisewith the pin and stoped behind the pin, which filled the cavity left by moving pin.③The texture components were analyzed along the ND direction on the differentlevels of the welding joint. On the0.35mm layer,texture component in SZ was Cube{100}<001>, the texture components of other regions were Cube {100}<001> andCopper {112}<111>; On the1.35mm layer, the texture componentofSZ wasBrass{110}<112>, TMAZ onAS and RS were Brass{110}<112> andCopper{112}<111>, HAZ on the AS were Cube{100}<001> and Brass{110}<112>,HAZ on the RS were Copper{112}<111> and Cube{100}<001>; On the2.35mm layer, the texture component was <111>//ND directed to TD about50°. On the3.35mm layer,the texture component was <111>//ND directed to TD about50°, and rotatedanticlockwise about30°. The texture compenent on AS and RS in TMAZ wasS{123}<634> and Copper{112}. The other regions kept same as BM.④Bymicrohardness and ECC, it showed microhardness distribution of differentlevels were same, the highest hardness appeared in SZ, the lowest hardness appearedinBM. The distribution of second phase were also same of all levels and the amount ofthe second phase was less. The distribution of the second phase inHAZ was same as BM,the second phase inTMAZ was broken by the stirring tool, the second phase in SZ wasbroken and dissolved by the mechanical stirring and cycle heat firstly, and in thesubsequent cooling processthe refined second phase was precipitated.