The underwater friction stir processing is used for development of aluminum metal matrix composite (AA2219-Y2O3) foam. For development of foam, holes with different diameter in the mid thickness of plate were filled with a mixture of TiH2 and aluminum powder and underwater friction stir processing was used to mix this mixture in aluminum metal matrix composite. Then precursors extracted from the processed zone and heated upto 650°C in a furnace for development of foam. The effect of diameter of hole, number of passes and the tool rotation direction has been studied on the foam cell size and static and dynamic compressive behavior of the foam. It is found that as the diameter of hole increases, the size of pores increases. The distribution of pores is better with higher number of passes and increasing the hole diameter. The quality of foam further improves by reversing the tool rotation direction. The developed foam has different pore size varies from 0.7 to 2.7 mm depends on the FSP parameters. Based on the size of pores and their distribution the relative density ranges from 0.1 to 0.78. The foam produced with 4 mm hole diameter has best static and dynamic compression properties.

Joining of dissimilar materials is difficult and challenging. Trend towards replacement of high density material (HDM) by low density material (LDM) is gaining importance in automotive industries. In the present work, friction stir welding (FSW) of high strength dissimilar materials i.e. aluminium alloy AA7475-T761 and stainless steel AISI 304 was conducted. The mechanical properties and microstructure of butt joint were investigated on using Taguchi L8 orthogonal array (OA). Different combinations of FSW parameters were used to obtain the maximum value of UTS. It was observed that most dominating parameter affecting UTS is tool rotational speed, contributing 42.19%, followed by traverse speed with 38.96% and shoulder diameter with 12.60%. The maximum UTS was observed 75.22% of base material AA 7475 (452MPa) under the optimum combination of parameters; tool rotational speed at 450 rpm, traverse speed 63 mm/min and shoulder diameter 14 mm. The microstructure of the resulted efficient joint shows appreciable variation in grain sizes in different zones and the micro hardness was found maximum in SZ on the retreating side.

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