A novel approach named large-load and low-speed friction stir welding was developed to joining Invar36 alloy. The stir zone was characterised by a mean grain size of 0.7 μm and high angle boundaries of 90.7%. Abundant twin boundaries were produced in the grains as well. The grain refinement mechanism is attributed to the combination of discontinuous dynamic recrystallisation and microshear-bands-assisted dynamic recrystallisation. A good combination of strength and ductility was achieved. This work provides a new insight for joining face-centred cubic metals or alloys with higher melmelting points, such as austenite stainless steel and Ni-base alloys.
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