Study of friction stir welding of 01420 aluminum–lithium alloy

In the present work, the AA7075-O was subjected to friction stir welding. The rotating and welding speeds were 630 rpm and 32 mm/min, respectively. The diameters of shoulder and pin were 30 and 5.7 mm, respectively. The length of threaded pin was 4.8 mm. The tensile, bending, and hardness tests were carried out on the friction stirwelded specimens. The results show that the strength of friction stir-welded sample was about 15 % (i.e., 25 MPa) higher than that of base metal. By contrast, the ductility of base metal was as much as twice that of friction stirwelded one. According to the obtained hardness profile, the maximum hardness was obtained for the stirred zone with a continuous decrease toward the base metal. This resulted in the formation of cracks after bending specimens prepared from weldment, while there was no sign of crack in the bent specimens taken from base metal. Besides, there are microstructural evolutions from the weldment toward the base metal. These include the variations in the size and distribution of precipitates. The precipitates were coarser in the heat-affected zone, while they were finer in the stirred zone.

Section: Bending Testmentioning

confidence: 99%

Microstructural evolution and mechanical properties during the friction stir welding of 7075-O aluminum alloy

Dehghani

Ghorbani

Soltanipoor³

2014

“…The state of art of friction stir welding of structural alloys beyond Al-alloys has been discussed in detail in Ref [8,11]. Also, some studies about Al-Li alloy show that the FSW can effectively avoid the loss of Li element as well as the hot cracks and pores generated frequently in fusion welded joints, and which can obtain the welds with better mechanical properties [5,12]. The principle of FSW procedure is easily simple.…”

Section: Introductionmentioning

confidence: 99%

Effect of welding parameters on microstructure and mechanical properties of friction stir welded joints of 2060 aluminum lithium alloy

Mao

Liu

et al. 2015

Two-millimeter-thick 2060 Al-Li alloy plates were friction stir welded under a welding speed of 95-150 mm/min and rotation speed of 750-1500 rpm. The effects of welding speed and rotation speed on formation quality, microstructure, secondary phase particles' transformation, and mechanical properties of the joints were investigated. The results show that defect-free joints are produced for varying friction stir welding (FSW) parameters, and nugget size increases firstly and then decreases with increasing rotation speed or decreasing welding speed. The weld nugget zones (WNZs) have fine dynamically recrystallized grains, and the size decreases to 7.9 μm with increasing rotation speed to 1180 rpm or decreasing welding speed to 118 mm/min, while the grains are coarsened at 1500 rpm or 95 mm/min. A similar trend occurs in the transformation of secondary phase particles, whose size is the smallest in WNZ at 1180 rpm-118 mm/min. All joints exhibit softened zones where the hardness is the lowest, and the joints fracture from WNZs or heat-affected zones. The joints welded at 1180 rpm-118 mm/min perform the highest ultimate tensile strength of 495 MPa, yield strength of 380 MPa, and elongation of 10.2 %. With increasing rotation speed or decreasing welding speed, the strengths and elongation of the joints increase firstly and then decrease.

“…Chen and Huang studied the influence of welding parameters on the microstructures and mechanical properties of electron beam-welded 8090 Al-Li alloy plates [3]. Wei et al and Shi et al carried out a study on 1420 Al-Li alloy by FSW and laser welding, respectively [4,5]. However, some difficulties are encountered in welding Al-Li alloy through these methods.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and mechanical properties of laser-MIG hybrid welding of 1420 Al-Li alloy

Yan

Gao

et al. 2012

This paper investigates the microstructure and mechanical properties of 1420 aluminum-lithium (Al-Li) alloy joints before and after heat treatment by CO 2 lasermetal inter gas (MIG) hybrid welding. The 5-mm-thick 1420 Al-Li alloy plates were welded by CO 2 laser-MIG hybrid welding. Full penetration joints without any defects were produced. Optic and scanning electron microscopy were used to study the microstructure and fractograph characteristics. The results show that the microstructures of the heat-affected zone (HAZ) and fusion zone exist as a predominantly discontinuous equiaxed dendritic structure and as a fine cellular dendritic structure, respectively. After heat treatment, the microstructures change from dendritic structure to a spheroidal crystal; the grain size of fusion zone is obviously larger than that of the base metal and the HAZ. Furthermore, the hardness recovers substantially to a level similar to that of the parent material. The tensile strengths of the joints in the as-welded condition and after heat treatment are 223 and 267 MPa, reaching up to 57 and 68 % of the parent materials' strength, respectively. The fractographs show that the joint as-welded condition exhibits the characteristics of dominated dimples and a small amount tear ridges, which are associated with the mixed ductile and brittle facture mechanisms. The fracture mode transforms from a transgranular to an intergranular after heat treatment; cleavage cracking coupled with an intergranular microvoid coalescence fracture mechanism occurs.