Abstract
High strength nickel based alloys are used in a multitude of advanced systems where lightweight, high power density mechanical power transmission systems are required. Components such as gears, bearings and shafts could be made significantly smaller and more durable if a major improvement in nickel based alloy mechanical properties could be achieved. An important refinement in grain size (includes nanometric level) is thought to be a promising method for achieving fundamental improvements in mechanical properties. Grain size is known to have a significant effect on the mechanical behavior of materials. One of the most favorable methods of achieving extreme grain refinement is by subjecting the materials to severe plastic deformation (SPD). The principal micro-structural variations in superalloys are the precipitation amount and morphology, grain size and the distribution of carbide precipitation that could reduce the mechanical properties of the alloys. This work shows optical and transmission electron microscopy analysis and also hardness data after severe plastic deformation (pure shear stress).
Highlights
Despite the physical and mechanical properties of metals are determined by several factors, the average size of grain of material usually plays a very important role and is often a dominant factor in determining the properties and the final application of metals
One of the most favorable methods of achieving extreme grain refinement is by subjecting the materials to severe plastic deformation (SPD)
The grain sizes of commercial alloys are generally manufactured for specific applications, through predetermined thermo-mechanical treatments in which the alloys are subjected to specific regimes of temperature and mechanical tests
Summary
Despite the physical and mechanical properties of metals are determined by several factors, the average size of grain of material usually plays a very important role and is often a dominant factor in determining the properties and the final application of metals. SPD of any high-strength material, such as nickel alloy 600, by pressing or twisting in high pressure is inherently difficult due to tooling requirements [6] Among these methods, pressing in SPD is one of the simplest methods of deformation, which under ideal conditions occurs by simple shear. This technique was originally developed by Segal et al [7], aiming to introduce severe plastic deformation in materials without changing the cross-section of sample, and it is possible to repeat the process several times to increase the level of imposed deformation [8] [9] [10]. At each even numbered pass, shear bands nearly disappear and only subgrains are present inside the original grains [1] [11] [12] [13] [14] [15]
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