Modelling of strengthening mechanisms in wrought nickel-based 825 alloy subjected to solution annealing

• Wrought nickel‐based Alloy 825 is widely used in the oil and gas industries, attributed toits high strength at temperatures up to 540 °C. However, differences in mechanical properties arisein finished components due to variations in both grain size and dislocation density. Numerous ex‐perimental studies of the strengthening mechanisms have been reported and many models havebeen developed to predict strengthening under thermomechanical processing. However, there aredebates surrounding some fundamental issues in modeling and the interpretation of experimentalobservations. Therefore, it is important to understand the evolution of strain within the materialduring the hot‐forging process. In addition, there is a lack of research around the behavior duringhot deformation and subsequent stabilization of Alloy 825. This article investigates the origin of thisstrength and considers a variety of strengthening mechanisms, resulting in a quantitative predictionof the contribution of each mechanism. The alloy is processed with a total forging strain of 0.45, 0.65,or 0.9, and subsequent annealing at a temperature of 950 °C, reflecting commercial practice. Themicrostructure after annealing is similar to that before annealing, suggesting that static recovery isdominant at this temperature. The maximum yield strength and ultimate tensile strength were348 MPa and 618 MPa, respectively, obtained after forging to a true strain of 0.9, with a ductility of40%. The majority of strengthening was attributed to grain refinement, the dislocation densities thatarise due to the large forging strain deformation, and solid solution strengthening. Precipitatestrengthening was also quantified using the Brown and Ham modification of the Orowan bowingmodel. The results of yield strength calculations are in excellent agreement with experimental data,with less than 1% difference. The interfacial energy of Ti(C,N) in the face‐centered cubic matrix of. These results can bethe current alloy has been assessed for the first time, with a value of 0.8 mJm−2used by future researchers and industry to predict the strength of Alloy 825 and similar alloys, es‐pecially after hot‐forging.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

Nyckelord

Alloy 825; strain level; strength properties; annealing; strengthening mechanisms

Publikations- och innehållstyp

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