Microstructure and mechanical properties’ modification of friction stir welded Invar 36 alloy joint

ABSTRACT

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 melting points, such as austenite stainless steel and Ni-base alloys.

KEYWORDS:

• Invar 36 alloy
• friction stir welding
• recrystallisation
• grain boundaries
• mechanical properties

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was financial supported by National Natural Science Foundation of China (No. 51805145), Natural Science Foundation of Jiangsu Province (No. BK20160284) and Fundamental Research Funds for the Central Universities of PR China (No. 2018B22514).