Warm Rolled Alloy Research Articles

Outstanding high-temperature strength-ductility combination in inconel 718 alloy by warm rolling and simplified aging treatment

In the present study, a comparative study was conducted with the cold-rolled Inconel 718 alloy and warm-rolled Inconel 718 alloy. The influences of deformation process and aging treatment on microstructure evolution and tensile properties of Inconel 718 alloy were investigated. The results showed that some fresh recrystallized grains can be observed in the warm-rolled and subsequent aged samples, resulting in refined microstructures of the warm-rolled and aged samples. Besides, the warm rolling process can accelerate the precipitation of γ" strengthening phase. The peak hardness (∼560 H V) of the warm-rolled sample was obtained after aging at 720 °C for 2 h, which far exceeded that of cold-rolled Inconel 718 alloy even aged for 8 h (∼520 H V). According to the TEM analysis, the fraction and size of γ" particles of the warm-rolled sample after 2 h aging were about 10.3% and 5.9 nm, which was higher than the cold-rolled sample with the same aging treatment (7.6% and 2.9 nm). Moreover, most of the γ" particles in the warm-rolled sample after simplified aging was nearly spherical, rather than the disk-shaped in the traditional two-stage aging Inconel 718 alloy. Compared with cold-rolled and aged materials, the warm-rolled alloy after aging exhibited superior mechanical properties. When deformed at 650 °C, the tensile strength and elongation of warm-rolled samples after aging treatment were 1247.6 MPa and 18.7%, while the corresponding values of cold-rolled samples after aging were 1162.5 MPa and 13.6%. The excellent strength-ductility combination of Inconel 718 alloy was linked with refined grains, numerous modified precipitates, and partial recrystallized structure with great dislocation density and many dislocation cells. As a result, warm rolling may provide an effective way to simplify the traditional 18 h two-stage aging to just 2 h single-stage aging treatment, and meanwhile, to improve the mechanical properties of Inconel 718 alloy.

Effect of Rolling Treatment on Microstructure, Mechanical Properties, and Corrosion Properties of WE43 Alloy.

Magnesium alloys show broad application prospects as biodegradable implanting materials due to their good biocompatibility, mechanical compatibility, and degradability. However, the influence mechanism of microstructure evolution during forming on the mechanical properties and corrosion resistance of the magnesium alloy process is not clear. Here, the effects of rolling deformation, such as cold rolling, warm rolling, and hot rolling, on the microstructure, mechanical properties, and corrosion resistance of the WE43 magnesium alloy were systematically studied. After rolling treatment, the grains of the alloy were significantly refined. Moreover, the crystal plane texture strength and basal plane density decreased first and then increased with the increase in rolling temperature. Compared with the as-cast alloy, the strength of the alloy after rolling was significantly improved. Among them, the warm-rolled alloy exhibited the best mechanical properties, with a tensile strength of 346.7 MPa and an elongation of 8.9%. The electrochemical experiments and immersion test showed that the hot working process can greatly improve the corrosion resistance of the WE43 alloy. The hot-rolled alloy had the best corrosion resistance, and its corrosion resistance rate was 0.1556 ± 0.18 mm/year.

Good combination of strength and corrosion resistance in an Al-Cu-Mg alloy processed by a short-cycled thermomechanical treatment

The mechanical properties, corrosion resistance and microstructure of an Al-Cu-Mg alloy subjected to cryorolling, warm rolling and short-time aging were investigated. The alloy underwent cryorolling and warm rolling exhibited higher hardness than the cryorolled alloy before and after aging. Microstructural results revealed that precipitation was promoted in the warm rolled alloy. After appropriate aging, the warm rolled alloy showed significant enhancement of strength and corrosion resistance with good ductility in comparison with the peak-aged alloy. The improved properties of the warm rolled alloy after aging was mainly attributed to more homogeneous distribution of nanosized precipitates in the grain interior and the absence of continuous grain boundary precipitates.

Effect of Warm Rolling on Micro-deformation Behavior and Mechanical Properties of Columnar-grained Fe-6. 5 mass%Si Alloy

AbstractMicro-deformation behavior and mechanical properties of columnar-grained Fe-6. 5 mass%Si alloy before and after warm rolling were investigated by means of micro-indentation and three-point bending tests. The results show that the columnar-grained Fe-6. 5 mass%Si alloy before warm rolling presents sink-in mode of micro-indentation, while pile-up mode with a number of arc-shaped deformation bands exists in the warm-rolled alloy. Compared with that of the alloy before warm rolling, the maximum bending fracture stress and maximum bending fracture deflection of the warm-rolled alloy are increased by 96% and 50%, respectively. The different micro-deformation behavior and mechanical properties of the columnar-grained Fe-6. 5 mass%Si alloy are ascribed to the changes of dislocation density, dislocation configuration and long-range order degree, which significantly improve the room temperature plasticity of the alloy after warm rolling.

Effect of Prior Recovery Treatment on the Evolution of Cube Texture During Annealing of Severely Warm-Rolled Al-2.5 wt pctMg Alloy

The effect of prior recovery on the evolution of cube texture ({001}〈100〉) in severely warm-rolled and annealed Al-2.5 wt pctMg alloy was studied. The Al-2.5 wt pctMg alloy was warm rolled to 97 pct reduction in thickness at 473 K (200 °C). The warm-rolled sheets were isochronally annealed for 1 hour at temperatures ranging from 523 K to 673 K (250 °C to 400 °C) without and with prior recovery treatments. In case of prior recovery, the sheets were pre-treated at 473 K (200 °C) for different time intervals ranging from 3.6 × 103 seconds (1 hour) to 8.64 × 104 seconds (24 hours) before the annealing. The warm-rolled alloy showed finely subdivided lamellar structure and strong presence of pure metal type texture. The annealed materials without any prior recovery treatment showed strong cube texture after annealing which could be attributed to the oriented nucleation of cube grains resulting from the preferentially recovered structure of cube regions in the warm-rolled state. In contrast, the cube texture was significantly weakened in materials subjected to different prior recovery treatments. The prior recovery treatments resulted in homogenous recovery which was confirmed by microstructural, textural, and conductivity measurements. Homogenous recovery eliminated the nucleation advantage of cube regions originating from the preferentially recovered structure and weakened the cube texture significantly. The present results indicated that prior recovery treatment could be effectively used to control recrystallization cube texture in severely warm-rolled aluminum alloys.

Relating Grain Misorientation to the Corrosion Behaviour of Low Copper 7xxx Aluminium Alloys

High strength aluminium alloys provide benefits in vehicle efficiency and reduced energy consumption. Weldable, low copper 7xxx aluminium alloys are being developed for body-in-white production. Here, the influences of thermomechanical history on microstructure and, consequently, on the corrosion behaviour of lean 7xxx aluminium alloy sheet have been investigated. Cold worked microstructures in the alloys studied are susceptible to sub-surface cracking after accelerated corrosion testing. High resolution transmission electron microscopy (HAADF) with allied EDX analysis of a warm rolled alloy has revealed significant differences between some grain boundaries, showing differences in grain boundary precipitate distribution, which is influenced by grain misorientation and thermomechanical processing history. Possible relationships between the previously described phenomena are being sought. Electron backscatter diffraction has been employed to provide crystallographic information concerning grain orientation relationships from specific areas surrounding the attacked microstructure.

Nano-Scaled Microstructure and Tensile Behavior of Spray-Formed and Subsequently Worked Al-8Fe-2Mo-2V-1Zr Alloys

Room temperature tensile behavior of nano-structured Al-8Fe-2Mo-2V-1Zr alloy prepared by spray forming and subsequent hot extrusion (as-received) was investigated by tensile test in relation to microstructure and processing step. The microstructure of spray formed and extruded sample is composed of equiaxed grain structure of about 500 nm with finely dispersed intermetallic phases such as Al 3 (Fe, Mo, V, Zr) and Al 6 (Fe, Mo, V, Zr) at grain boundaries and grain interiors. The average particle size of dispersoids was measured to be 40 nm. Warm rolling of extruded sample accelerates an occurrence of dispersoids less than 20 nm. The elongation of warm rolled alloy is higher than that of as-received one, although yield strength decreases by warm rolling. It is suggested that warm rolling of as-received alloy causes the increase in elongation and decrease in yield strength due to decreasing content of solid solution strengtheners by activated diffusion process to form a precipitate in supersaturated Al matrix phase. Details will be discussed in correlation with XRD, SEM, TEM analyses.

Effect of Deformation Temperature on High Strain Rate Superplastic Properties in PM 2024Al-Fe-Ni Alloys

High strain rate superplastic properties of high strength PM 2024Al-3Fe-5Ni alloys with or without 0.3 mass % Zr addition have been investigated at a wide testing temperature range of 673K- 793K. The alloys were fabricated by an air atomization technique, followed by extrusion at 623 K and warm rolling at 523K. After the warm rolling, these alloys exhibited ultrafine grained matrix structure. Heating rate to the testing temperatures influenced the superplastic properties of the warm rolled alloy sheets remarkably. After the slow heating (0.8K/s) up to the testing temperature, PM 2024Al-3Fe-5Ni alloy showed the relatively low maximum elongation of about 250% (m=0.35) at a strain rate of 3 S - even at 773K, which is very close to the solidus temperature of the matrix alloy. However, in the case of the rapid heating rate (2.6K/s) condition, the superplastic properties were improved remarkably at the temperature range between 713K and 773K, due to the suppression of microstructure coarsening before testing. Therefore, the fine grain structure capable of grain boundary sliding was considered to be always necessary for the high strain rate superplaticity.

Superplastic behavior of thermomechanically treated P/M 7091 aluminum alloy

The superplastic behavior of thermomechanically treated P/M 7091 aluminum alloy was assessed in the temperature range of 573 to 773 K. The thermomechanical treatment (TMT) comprised of three steps of solution treatment, overaging, and warm rolling. There are large η-phase (MgZn2) precipitate particles of average size of 1.30 μm in the overaged condition. The warm-rolled alloy undergoes continuous recrystallization at the test temperatures of 573 and 623 K, exhibiting a maximum tensile elongation of 450 pct at 573 K and a strain rate of 8 × 10−5 s−1. The precipitate particles play a major role in the process of continuous recrystallization. For a given volume fraction of precipitate particles and constant amount of warm rolling (in the course of TMT), an optimum precipitate particle size is expected to maximize the rate of continuous recrystallization and render the finest recrystallized grain size. The warm-rolled alloy undergoes static recrystallization at temperatures above 673 K. The grain growth accompanying the deformation at these test temperatures limits the tensile ductility to a lower value. Irrespective of the test temperature and strain rate, the specimens undergo extensive cavitation when deformed at elevated temperatures.

Microstructural changes during superplastic deformation of an Al-Li-Cu-Mg-Zr alloy

Fine grain size is one of the essential conditions for polycrystalline materials to have superplasticity. Several methods are available for grain refinement. Recrystallization has been used extensively for the grain refinement of superplastic quasi-single-phase aluminium base alloys. One of the characteristics of superplastic deformation is that the fine grain sizes do not change substantially even after several hundreds of per cent strain [1, 2]. The grain size stabilization provided by the precipitate pinning has been widely used as an explanation of the above characteristic. An early suggestion has also been made that recrystallization plays an important role in grain size stabilization during the deformation of superplastic alloys [3, 4]. Deform-induced recrystallization during the initial stage of superplastic deformation of a warm-rolled AI-Li base alloy has been well known [5, 6]. Chokshi et al. [7] have found that the coarse surface grains formed by annealing before the tensile testing of an AI-Li base alloy recrystallized dynamically to produce a fine-grained microstructure on the surface of the specimen. This letter deals with the microstructural changes of a warm-rolled AI-Li-Cu-Mg-Zr alloy during superplastic deformation by means of transmission electron microscopy (TEM). It is demonstrated that the fine recrystallized grains formed by deformationinduced recrystallization during the initial stage of superplastic deformation recrystallize dynamically and repeatedly during the following stable superplastic deformation. The AI-Li base alloy and the deformation conditions used in this study were the same as those described in [8]. Microstructural studies were conducted on the specimens which were unloaded from superplastic tensile tests at a constant strain rate of 3 x 10-4s -1 by interrupting the test. For TEM observation the specimens were prepared by the conventional double-jetting method. A Philips CM12/STEM electron microscope was used to study the internal structure of the specimen. The misorientations of the grain boundaries of different specimens were measured by a simple and convenient method innovated by Liu [9], and more than 100 boundaries were measured for one specimen. Histograms were plotted to show the changes of misorientations occurring during superplastic deformation. The microstructure of the warm-rolled alloy is shown in Fig. la. On heating to the superplastic test temperature (515 °C) for about 5 rain, a subgrain structure was developed which was approximately 2/xm in average diameter (Fig. lb) and the misorientations between the subgrains was within a few degrees (Fig. lc). Fig. 2 shows the changes of the misorientations of grain boundaries with the strain during superplastic deformation at a strain rate of 3 x 10 .4 s -1. These histograms of misorientations indicate a progressive shift to higher misorientations with strain, with an