Citation: Sasmito, A.; Ilman, M.N.;
Iswanto, P.T.; Muslih, R. Effect of
Rotational Speed on Static and
Fatigue Properties of Rotary Friction
Welded Dissimilar AA7075/AA5083
Aluminium Alloy Joints. Metals 2022,
12, 99. https://doi.org/10.3390/
met12010099
Academic Editors:
Alberto Campagnolo and
Alberto Sapora
Received: 30 November 2021
Accepted: 29 December 2021
Published: 4 January 2022
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Article
Effect of Rotational Speed on Static and Fatigue Properties of
Rotary Friction Welded Dissimilar AA7075/AA5083 Aluminium
Alloy Joints
Agus Sasmito
1,2
, Mochammad Noer Ilman
1,
* , Priyo Tri Iswanto
1
and Rifai Muslih
3
1
Department of Mechanical and Industrial Engineering, Universitas Gadjah Mada,
Yogyakarta 55281, Indonesia; agus.sasmito@brin.go.id (A.S.); priyotri@ugm.ac.id (P.T.I.)
2
Badan Riset dan Inovasi Nasional (BRIN), Serpong 15314, Indonesia
3
National Nuclear Energy Agency of Indonesia (BATAN), Serpong 15314, Indonesia; rifai@batan.go.id
* Correspondence: ilman_noer@ugm.ac.id; Tel.: +62-813-2955-9977
Abstract:
In this work, rotary friction welding processes of dissimilar AA7075/AA5083 aluminium
alloy rods with the diameter of 15 mm were performed at varying rotational speeds, typically 370 to
2500 rpm. The aim of this research is to improve mechanical properties, in particular, strength and
fatigue performance of the weld joints. Several experiments including macro and microstructural
examinations, Vickers microhardness measurements, tensile tests, fatigue tests and residual stress
measurements were carried out. Results showed that at higher rotational speeds, typically 540 rpm
or above, the dissimilar AA7075/AA5083 rotary friction weld joints revealed a static fracture in the
AA5083 base metal side, indicating that the joint efficiency is more than 100%. It seemed that the best
weld joint was achieved at the rotational speed of 1200 rpm, in which the friction heat was sufficient
to form metallurgical bonding without causing excessive flash and burn-off. In such a condition,
the fatigue strength of the weld joint was slightly higher than AA5083 base metal, but it was lower
than AA7075 base metal. It was confirmed that the crack origin is observed at the interface followed
by fatigue crack growth towards AA5083 side, and the growth of crack seemed to be controlled by
microstructure and residual stress.
Keywords:
rotary friction welding; dissimilar AA7075/AA5083 weld; rotational speed; tensile
strength; residual stress; fatigue
1. Introduction
Over the years, aluminium alloys such as 5xxx series (Al-Mg alloys) and 7xxx series (Al-
Zn alloys) have been used for lightweight structures in the transportation industry due to
their excellent properties such as high strength-to-weight ratio, acceptable fatigue properties
resistance and good machinability [
1
,
2
]. AA5083 is the main aluminium alloy of 5xxx
series since it finds wide applications such as ship hulls, automobiles and various welded
structures exposed to corrosive environment, e.g., offshore oil rigs [
3
,
4
]. On the other hand,
AA7075 and its 7xxx series are among the principal choices for aircraft structures and
automotive applications [
5
]. In terms of weldability, AA5083 is readily welded by various
welding processes [
6
], and in contrast, AA7075 is considered to be unweldable by fusion
welding due to solidification cracking [
7
]. Therefore, dissimilar metal welding of these two
materials seems challenging and it needs an appropriate joining method.
Rotary friction welding (RFW) is a solid-state welding that has gained importance in
the manufacturing industry due to its advantages over other joining processes including
high reproducibility, short production time and low energy input. In addition, the welding
process can be easily automated, and it is feasible for joining dissimilar materials [
8
,
9
]. As
the name implies, RSW employs rotation to produce friction heat between two contacting
surfaces combined with axial force to accomplish friction welding. In such a condition,
Metals 2022, 12, 99. https://doi.org/10.3390/met12010099 https://www.mdpi.com/journal/metals
