The precipitating behavior of δ phase in GH4169G alloy at 910°C was investigated and a novel process for achieving fine-grained GH4169G sheet with average grain size of ASTM13 was proposed. Globular δ phase precipitation precedes that of the plate-like δ phase, forming at grain boundary first and later in grain. After globular δ phase reaches a peak volume, it begins to transform into plate-like in grain boundary, and then the plate-like δ phase forms in grain in certain direction. The grain-fined process includes the following steps:(1) solution treated at a proper temperature, then air cooled; (2) soaked for δ phase precipitation; (3) cold rolled; (4) annealed for recrystallization. Microstructure analysis from optical microscopy (OM) and scanning electron microscopy (SEM) revealed that both plate-like and globular δ phase remarkably restrained the grain growth during annealing recrystallization. The optimum parameters for the grain refinement were determined finally.
AbstractMetastable austenitic stainless steels may transform to martensite when subjected to cold rolling. Upon subsequent annealing the martensite reverts back to ultra-fine grained austenite. Based on this concept, nano/submicron austenitic grains have been produced in a 63% cold rolled commercial AISI 301LN subjected to annealing treatments at 600°C, 800°C and 1000°C for 1, 10 and 100 seconds.Transmission Electron Microscopy (TEM) observations show the formation of equiaxed austenitic grains as small as ∼ 200nm in samples annealed at 800°C, and a dramatic increase in grain size as the annealing temperature and duration is increased. Additional tensile tests indicate that samples annealed at 800°C for 1 second exhibit a yield strength of ∼ 740 MPa and an total elongation of ∼ 45%. This combination of strength and ductility is excellent exceeding those of conventionally annealed steels (σy=350 MPa; Ductility ∼ 40%) or cold-rolled steels (σy=650 MPa; Ductility ∼ 30%).Finally, a correlation between the observed grain sizes and mechanical properties, in particular the yield strength, is obtained. Preliminary analysis indicates that the Hall-Petch equation can satisfactorily relate the observed yield strength with corresponding grain sizes.
Thermo-mechanical treatment, in particular, cryo-rolling is a unique technique to produce super high strength AA-7xxx aluminium alloys with ultra-fine grained structure. In order to conduct the rolling at room temperature and cryo-temperature (liquid N2 (-190°C)), the AA-7xxx alloy ingot was rolled from 6mm to 1mm with 85% reduction in thickness. Optical microscopy, XRD, electron microscopy, hardness and tensile testing were conducted on the rolled alloy for understanding the phase changes and evaluating the mechanical properties. The alloy rolled at liquid nitrogen (LN2) exhibits very high strength with reasonable ductility. Corrosion behaviour of AA-7xxx series aluminium alloy various conditions in NaCl (3.5%) solution were investigated. Cold rolled and cryo rolled alloy exhibits better corrosion resistance than that of cast.
In the whole manufacturing chain of aluminium products, hot rolling significantly impacts the obtaining of favourable microstructures and desired mechanical properties of final products. The determination of crucial differences between the reverse hot rolling on a single-stand mill and the tandem hot rolling on a tandem-stand mill presented a major challenge. Besides the grain-size distribution in the microstructure’s cross-section, the crystallographic textures of hot-rolled strips were also determined and compared. The alternating band areas of a coarse-grained microstructure and fine-grained microstructure due to reverse hot rolling and, especially, the appearance of extremely fine grains on the surfaces present limitations compared to the tandem hot rolling. For subsequently cold-rolled foils, classical mechanical properties were measured. Besides, the usefulness of EN AW-8021B foils with a thickness of 60 µm for pharmaceutical-packaging applications was tested with a burst test. A minor but important difference of 1 % in the elongation is shown for the convex height increased by 1 mm.
Abstract
WC-3015 is a columbium-base alloy developed for structural applications in high-temperature oxidizing environments. It is characterized by good oxidation resistance, good mechanical properties and compatibility with silicide coatings. Cold-rolled sheet can be joined and welded without cracking. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on forming, heat treating, machining, joining, and surface treatment. Filing Code: Cb-21. Producer or source: Wah Chang, a Teledyne Corporation.
The INFLUENCE OF THE HOT-ROLLING TECHNIQUE FOR EN AW-8021B ALUMINIUM ALLOY ON THE MICROSTRUCTURAL PROPERTIES OF A COLD-ROLLED FOIL