Fabrication of high-quality Ti joint with ultrafine grains using submerged friction stirring technology and its microstructural evolution mechanism

Han

Peng

et al. 2019

175

Magnesium (Mg) alloys have been extensively used in various fields, such as aerospace, automobile, electronics, and biomedical industries, due to their high specific strength and stiffness, excellent vibration absorption, electromagnetic shielding effect, good machinability, and recyclability. Friction stir processing (FSP) is a severe plastic deformation technique, based on the principle of friction stir welding. In addition to introducing the basic principle and advantages of FSP, this paper reviews the studies of FSP in the modification of the cast structure, superplastic deformation behavior, preparation of finegrained Mg alloys and Mg-based surface composites, and additive manufacturing. FSP not only refines, homogenizes, and densifies the microstructure, but also eliminates the cast microstructure defects, breaks up the brittle and network-like phases, and prepares fine-grained, ultrafine-, and nano-grained Mg alloys. Indeed, FSP significantly improves the comprehensive mechanical properties of the alloys and achieves low-temperature and/or high strain rate superplasticity. Furthermore, FSP can produce particle-and fiber-reinforced Mg-based surface composites. As a promising additive manufacturing technique of light metals, FSP enables the additive manufacturing of Mg alloys. Finally, we prospect the future research direction and application with friction stir processed Mg alloys.

Section: Preparation Of Fine- Ultrafine- and Nano-grained Mg Alloysmentioning

confidence: 99%

Friction Stir Processing of Magnesium Alloys: A Review

Han

Peng

et al. 2019

175

“…Friction stir welding (FSW), a kind of advanced solid-state welding technique with relatively low heat input [10,11], has been successfully applied to the joining of aluminum and magnesium alloys [12][13][14][15]. With the continuous development of welding tools, FSW has gradually demonstrated its merits in the welding of high melting point materials such as steels, titanium alloys and superalloys [16][17][18][19]. Because of the absence of melting during welding, FSW can ameliorate the problems in fusion welding and has shown great possibility of joining AUHSSs.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Evolution and Mechanical Behavior of Friction-Stir-Welded DP1180 Advanced Ultrahigh Strength Steel

Xie

et al. 2019

Friction stir lap welding of a DP1180 advanced ultrahigh strength steel was successfully carried out by using three welding tools with different pin lengths. The effects of the welding heat input and material flow on the microstructure evolution of the joints were analyzed in detail. The relationship between pin length and mechanical properties of lap joints was studied. The results showed that the peak temperatures of all joints exceeded A c3 , and martensite phases with similar morphologies were formed in the stir zones. These martensite retained good toughness due to the self-tempering effect. The formation of ferrite and tempered martensite was the main reason for the hardness reduction in heat-affected zone. The mechanical properties of the lap joints were determined by loading mode, features of lap interface and the joint defects. When the stir pin was inserted into the lower sheet with a depth of 0.4 mm, the lap joint exhibited the maximum tensile strength of 12.4 kN.

“…After FSW, the shape of the B 4 Cp hardly changed. However, the B 4 Cp was redistributed uniformly in the matrix and the number of the B 4 Cp with large aspect ratio was decreased in the NZ, resulting from the drastic plastic deformation of the Al alloy matrix and the particle/tool interaction, such as collision, during FSW [4,25,26]. Furthermore, the B 4 Cp size and aspect ratio were significantly reduced in the NZ as shown by the statistical result (Fig.…”

Section: Resultsmentioning

confidence: 89%

High-Speed Friction Stir Welding of T6-Treated B4Cp/6061Al Composite

Zan

et al. 2019

T6-treated 20 wt% B 4 Cp/6061Al sheets were joined under welding speeds of 400-1200 mm/min by friction stir welding (FSW) with a threaded cermet pin. The macro-defect-free FSW joints could be achieved at high welding speeds up to 1200 mm/min, but larger plunge depth was required at the welding speeds of 800 and 1200 mm/min to eliminate the tunnel defect. In the nugget zone (NZ) of the joints, the B 4 C particles were broken up and uniformly redistributed. The NZ exhibited lower hardness than the base metal (BM), and the hardness value almost did not change with increasing welding speed, attributable to the dissolution of precipitates. Compared with the BM, the joints showed lower tensile strength. As the welding speed increased from 400 to 800 mm/min, the joint efficiencies were nearly the same and up to ~ 73%. When the welding speed increased up to 1200 mm/min, the tensile strength significantly decreased, due to the occurrence of kissing bond defect at the bottom of the NZ. With increasing welding speed, the fracture location of the joints transferred gradually from the heat-affected zone to the NZ due to the kissing bond defects.