Abstract:In this paper, the microstructure and mechanical properties of Fe-36%Ni alloy after 90% reduction of cryorolling (CR) and subsequent annealing were investigated. The X-Ray diffraction (XRD) results indicated the existence of , phase transformation, and the measurement result of the ， volume fraction was 15%. Lath ， with average thickness of 29.3 nm was then observed by transmission electron microscope (TEM). After 90% reduction of CR, the ultimate strength (UTS) of the tested alloy was enhanced to 110… Show more
“…For the tensile test result as shown in Figure 1(d), the SZ exhibited excellent ultimate tensile strength and uniform elongation of 608 MPa and 49%, respectively, which was significantly optimised compared with that of the fusion welded, traditional FSW and severe plastic deformed Invar 36 alloy, and it seems has a good strength-ductility balance as similar as equal channel angular processed ones. Figure 1 (a) Surface appearance and (b) cross-sectional overview of the welded joint, (c) hardness profile measured across the weld mid-thickness, (d) relationship between uniform elongation and strength of Invar 36 alloy prepared by several processing methods [1-9, 15-18]. ‘AS’ and ‘RS’ in (b) mean advancing side and retreating side of the weld, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…(a) Surface appearance and (b) cross-sectional overview of the welded joint, (c) hardness profile measured across the weld mid-thickness, (d) relationship between uniform elongation and strength of Invar 36 alloy prepared by several processing methods [1-9, 15-18]. ‘AS’ and ‘RS’ in (b) mean advancing side and retreating side of the weld, respectively.…”
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.
“…For the tensile test result as shown in Figure 1(d), the SZ exhibited excellent ultimate tensile strength and uniform elongation of 608 MPa and 49%, respectively, which was significantly optimised compared with that of the fusion welded, traditional FSW and severe plastic deformed Invar 36 alloy, and it seems has a good strength-ductility balance as similar as equal channel angular processed ones. Figure 1 (a) Surface appearance and (b) cross-sectional overview of the welded joint, (c) hardness profile measured across the weld mid-thickness, (d) relationship between uniform elongation and strength of Invar 36 alloy prepared by several processing methods [1-9, 15-18]. ‘AS’ and ‘RS’ in (b) mean advancing side and retreating side of the weld, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…(a) Surface appearance and (b) cross-sectional overview of the welded joint, (c) hardness profile measured across the weld mid-thickness, (d) relationship between uniform elongation and strength of Invar 36 alloy prepared by several processing methods [1-9, 15-18]. ‘AS’ and ‘RS’ in (b) mean advancing side and retreating side of the weld, respectively.…”
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.
“…The scan speed of the XRD was 2° min −1 , and the scanned angle was between 40° and 100°. The volume fraction of α ′-M was evaluated by using the equations in [7,8]. Mechanical property tests were carried out on a WDW300 materials testing machine at RT with a constant crosshead speed of 1 mm/min.…”
Section: Methodsmentioning
confidence: 99%
“…More recently, we found that CR can significantly enhance the strength of the Fe–36%Ni alloy compared to RT rolling. In addition, both deformation twin (DT) and deformation-induced ( α ′-M) were detected during CR [7]. In this paper, the Fe–36%Ni alloy was cryorolled with thickness reduction from 20% to 90% and both the microstructural evolution and deformation mechanism were discussed.…”
In this paper, the microstructural evolution and deformation mechanism of the cryorolled Fe–36%Ni alloy was investigated. Deformation twinning was confirmed to be activated at the early stage of cryorolling (CR) and subsequently suppressed due to microstructure refinement. The existence of [Formula: see text] and [Formula: see text] peaks revealed that the [Formula: see text] ( α′-M) phase transformation was induced during the CR process. The stress-assisted martensite and strain-induced martensite were detected to be transformed at the grain boundary and intersection of deformation twins, respectively. Owing to the co-effect of the temperature raise and mechanical stabilisation, the α′-M phase transformation was suppressed during the CR process. Therefore, the amount of the α′-M was limited in the tested alloy.
“…Invar 36 alloy, which is an iron-nickel alloy with a composition in weight of 64% Fe and 36% Ni, is well known for its extremely low coefficient of thermal expansion (CTE) below Curie temperatures [1][2][3][4][5][6]. Benefiting from its extremely low expansion over a wide range of service temperatures, it has been extensively used as high precision material in engineering applications requiring high dimensional stability, such as precision instruments, space equipment, metrology devices, composite molds, and optical parts, etc.…”
The mechanical properties of laser powder bed fused (LPBFed) Invar 36 alloy have been limited by the presence of manufacturing defects. It is imperative to investigate the influence of these defects on the mechanical behavior of LPBFed Invar 36 alloy. In this study, in-situ X-ray computed tomography (XCT) tests were conducted on LPBFed Invar 36 alloy fabricated at different scanning speeds to examine the relationship between manufacturing defects and mechanical behavior. For LPBFed Invar 36 alloy fabricated at a scanning speed of 400 mm/s, the manufacturing defects were randomly distributed and tended to be elliptical in shape. Plastic deformation behavior was observed, and failure initiated from defects inside the material resulting in ductile failure. Conversely, for LPBFed Invar 36 alloy fabricated at a scanning speed of 1000 mm/s, numerous lamellar defects were observed mainly located between deposition layers, and their quantity was significantly increased. Little plastic deformation behavior was observed, and failure initiated from defects on the shallow surface of the material resulting in brittle failure. The differences in manufacturing defects and mechanical behavior are attributed to changes in input energy during the laser powder bed fusion process.
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