There has always been a question about which condition results in superior mechanical properties in friction stir spot welds: (i) when the tool tip penetrates into the lower sheet or (ii) when the tool tip does not touch it. Given the question, the effects of the tool penetration depth were investigated on the microstructure and mechanical behaviour of dissimilar Al-5083/St-12 joints produced by friction stir spot welding (FSSW). Two different processes named as non-penetrating and penetrating FSSW were used. Optical and scanning electron microscopes as well as microhardness and tensile–shear tests were utilised to examine the obtained joints. The results showed that the penetrating process led to the stronger joints with lower fracture energy. The differences were studied in the light of the joining mechanisms and the formation of Al/Fe intermetallic compounds.
ChenY. C., KomazakiT., KimY. G., TsumuraT. and NakataK.: ‘Interface microstructure study of friction stir lap joint of AC4C cast aluminium alloy and zinc-coated steel’, Mater. Chem. Phys., 2008, 111, 375–380. doi:10.1016/j.matchemphys.2008.04.038.
2.
ShenZ., ChenY., HouJ. S. C., YangX. and GerlichA. P.: ‘Influence of processing parameters on microstructure and mechanical performance of refill friction stir spot welded 7075-T6 aluminium alloy’, Sci. Technol. Weld. Join., 2015, 20, 48–57. doi:10.1179/1362171814Y.0000000253.
3.
VenukumarS., YalagiS. G., MuthukumaranS. and KailasS. V.: ‘Static shear strength and fatigue life of refill friction stir spot welded AA 6061-T6 sheets’, Sci. Technol. Weld. Join., 2014, 19, 214–223. doi:10.1179/1362171813Y.0000000181.
4.
ChenY., ChenJ., Shalchi AmirkhizB., WorswickM. J. and GerlichA. P.: ‘Microstructures and properties of Mg alloy/DP600 steel dissimilar refill friction stir spot welds’, Sci. Technol. Weld. Join., 2015, 20, 494–501. doi:10.1179/1362171815Y.0000000033.
5.
SarkarR., PalT. K. and ShomeM.: ‘Microstructures and properties of friction stir spot welded DP590 dual phase steel sheets’, Sci. Technol. Weld. Join., 2014, 19, 436–442. doi:10.1179/1362171814Y.0000000210.
6.
QiuR., IwamotoC. and SatonakaS.: ‘Interfacial microstructure and strength of steel/aluminium alloy joints welded by resistance spot welding with cover plate’, J. Mater. Process. Technol., 2009, 209, 4186–4193. doi:10.1016/j.jmatprotec.2008.11.003.
7.
MovahediM., KokabiA. H., Seyed ReihaniS. M. and NajafiH.: ‘Mechanical and microstructural characterisation of Al-5083/St-12 lap joints made by friction stir welding’, Procedia Eng., 2011, 10, 3297–3303. doi:10.1016/j.proeng.2011.04.544.
8.
BozziS., Helbert-EtterA. L., BaudinT., CriquicB. and KerbiguetJ. G.: ‘Intermetallic compounds in Al 6016/IF-steel friction stir spot welds’, Mater. Sci. Eng. A, 2010, 527, 4505–4509. doi:10.1016/j.msea.2010.03.097.
9.
BadarinarayanH., ShiY., LiX. and OkamotoK.: ‘Effect of tool geometry on hook formation and static strength of friction stir spot welded aluminium 5754-O sheets’, Int. J. Mach. Tools Manuf., 2009, 49, 814–823. doi:10.1016/j.ijmachtools.2009.06.001.
10.
YinY. H., IkutaA. and NorthT. H.: ‘Microstructural features and mechanical properties of AM60 and AZ31 friction stir spot welds’, Mater. Des., 2010, 31, 4764–4776. doi:10.1016/j.matdes.2010.05.005.
11.
ElrefaeyA., GoudaM., TakahashiM. and IkeuchiK.: ‘Characterization of aluminium/steel lap joint by friction stir welding’, J. Mater. Eng. Perform., 2005, 14, 10–17. doi:10.1361/10599490522310.
12.
ChenZ. W., YazdanianS. and LittlefairG.: ‘Effects of tool positioning on joint interface microstructure and fracture strength of friction stir lap Al-to-steel welds’, J. Mater. Sci., 2013, 48, 2624–2634. doi:10.1007/s10853-012-7056-0.
13.
ChenY. C. and NakataK.: ‘Effect of tool geometry on microstructure and mechanical properties of friction stir lap welded magnesium alloy and steel’, Mater. Des., 2009, 30, 3913–3919. doi:10.1016/j.matdes.2009.03.007.
14.
ShenZ., ChenY., HaghshenasM. and GerlichA. P.: ‘Role of welding parameters on interfacial bonding in dissimilar steel/aluminum friction stir welds’, Eng. Sci. Technol. Int. J., 2015, 18, 270–277. doi:10.1016/j.jestch.2014.12.008.
15.
TranV.-X., PanJ. and PanT.: ‘Effects of processing time on strengths and failure modes of dissimilar spot friction welds between aluminum 5754-O and 7075-T6 sheets’, J. Mater. Process. Technol., 2009, 209, 3724–3739. doi:10.1016/j.jmatprotec.2008.08.028.
16.
ZhangZ., YangX., ZhangJ., ZhouG., XuX. and ZouB.: ‘Effect of welding parameters on microstructure and mechanical properties of friction stir spot welded 5052 aluminum alloy’, Mater. Des., 2011, 32, 4461–4470. doi: 10.1016/j.matdes.2011.03.058
17.
MovahediM., KokabiA. H., Seyed ReihaniS. M. and NajafiH.: ‘Effect of tool travel and rotation speeds on weld zone defects and joint strength of aluminium steel lap joints made by friction stir welding’, Sci. Technol. Weld. Join., 2012, 17, 162–167. doi:10.1179/1362171811Y.0000000092.
18.
PadmanabhanR., OliveiraM. C. and MenezesL. F.: ‘Deep drawing of aluminium-steel tailor-welded blanks’, Mater. Des., 2008, 29, 154–160. doi:10.1016/j.matdes.2006.11.007.
19.
ZhangH. T., FengJ. C., HeP. and HacklH.: ‘Interfacial microstructure and mechanical properties of aluminium-zinc-coated steel joints made by a modified metal inert gas welding-brazing process’, Mater. Charact., 2007, 58, 588–592. doi: 10.1016/j.matchar.2006.07.008
