Multipass-friction Stir Processing (MFSP) of Ti-6Al-4V Alloy and Investigation of Flow Properties
08 Nov 2018-Vol. 422, Iss: 1, pp 012017
TL;DR: In this article, a multipass friction stir processing (MFSP) of the Ti-6Al-4V alloy was carried out at 600 tool rpm and 80 mm/min traverse speed, where the initial elongated α structure transformed to prior β grains, consisting of a mixture of acicular α'and very fine lamellar α colonies along with α layer grain boundary in stir zone (SZ).
Abstract: Multipass friction stir processing (MFSP) of the Ti-6Al-4V alloy was carried out at 600 tool rpm and 80 mm/min traverse speed. After first pass, the initial elongated α structure transformed to prior β grains, consisting of a mixture of acicular α'and very fine lamellar α colonies along with α layer grain boundary in stir zone (SZ). This subsequently transformed to equiaxed α grain via dynamic recrystallization (DRX) process. With the increase in the number of FSP passes the fraction of equiaxed α grains was found to increase, reaching almost fully equiaxed α structure in SZ upon completion of the fifth pass. Flow properties of MFSP Ti-6Al-4V alloy were investigated by differential strain rate test carried out at 927°C. There appears no significant variation in the strain rate sensitivity index (m ≥ 0.3) values between as received Ti-6Al-4V alloy and MFSP Ti-6Al-4V alloy specimens.
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15 Oct 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the typical welding defects of friction stir welding joint for 5456 aluminum alloy were analyzed and discussed, respectively, by using optical microscopy (OM), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscope (SEM).
Abstract: The external factors on the friction stir welding defects are so abundant that the experiments of friction stir welding were conducted for 5456 aluminum alloy. With the changes of the tool tilt angle and material condition, defects can be generated. These defects can be conventional ones (lack of penetration or voids), or lazy S, which are unique to friction stir welding. However, the origin of the defects remains an area of uncertainty. In this study, an attempt has been made to investigate the formation of these defects. The typical welding defects of friction stir welding joint for 5456 aluminum alloy were analyzed and discussed, respectively, by using optical microscopy (OM), energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscope (SEM). The microscopic examination of the nugget zone and fracture location of the weld confirms that the tilt angle can change the plastic material flow patterns in the stir zone and accordingly control the weld properties. In addition, the oxide layer from the initial butt surface during FSW is dispersed at the grain boundary. These A12O3 particles are actually the major cause of failure of the joint.
268 citations
TL;DR: In this paper, a Mg-Al-Zn casting was subjected to friction stir processing (FSP) and subsequent aging, which resulted in significant breakup and dissolution of the coarse, network-like eutectic β-Mg17Al12 phase distributed at the grain boundaries and remarkable grain refinement, thereby improving significantly the tensile properties of the casting.
257 citations
25 Jun 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: Friction stir welding (FSW) was applied to 3mm-thick Ti-6Al-4V plates under different rotational speeds as discussed by the authors, and failure-free welds were successfully produced at rotational speed of 400 and 500rpm.
Abstract: Friction stir welding (FSW) was applied to 3 mm-thick Ti–6Al–4V plates under different rotational speeds. Defect-free welds were successfully produced at rotational speeds of 400 and 500 rpm. The base material (BM) had a deformed α/β lamellar microstructure. FSW produced a full lamellar structure with refined prior β grains in the SZ, while the HAZ contained a bimodal microstructure consisting of the equiaxed primary α and α/β lamellar structure within the prior β structure. An increase in rotational speed increased the sizes of α colonies and prior β grains. The SZ exhibited higher hardness than the BM, with the lowest hardness found in the HAZ. Results of the transverse tensile test showed that all welds fractured in the HAZ and that they exhibited lower strength and elongation than the BM. The tensile test for only the SZ showed it to be characterized by higher strength and elongation than the BM.
240 citations
25 Oct 2003-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a novel technique for producing high-strain-rate superplastic (HSRS) microstructure via friction stir processing (FSP) in a commercial 2024 Al has been demonstrated.
Abstract: A novel technique for producing high-strain-rate-superplastic (HSRS) microstructure via friction stir processing (FSP) in a commercial 2024 Al has been demonstrated. A maximum ductility of ∼525% has been achieved at a strain rate of 10 −2 s −1 and 430 °C. Current results suggest that friction stir processing can be developed as a simple yet effective technique for producing microstructure amenable for superplasticity at high strain rates and/or lower temperatures and at lower flow stresses.
223 citations
TL;DR: In this paper, the fatigue life improvement was attributed to significant grain refinement, homogenization of the microstructure, and the elimination of porosity of A356 alloys.
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