| dc.description.abstract | This master thesis in material science aimed to investigate the influence of increased
degree of cold rolling reduction of precipitation formation in commercially produced
Nickel-base superalloy Inconel 718, and evaluate the mechanical properties. The
research involved mechanical testing through tensile testing and Vickers microhardness
testing, accompanied by microstructural investigation with optical and scanning
electron microscope.
The material was machined into thin strips and solution heat treated at 1100◦C for
1 hour and water quenched to normalize the material. Subsequently, the samples
underwent cold rolling with a constant reduction down to 20% and 50% of their
original thickness, followed by a two-step precipitation hardening treatment at
720◦C for 8 hours, furnace cooling to 650◦C for another 8 hours and air cooling to
room temperature.
The mechanical testing revealed a clear increase in hardness, yield strength and
tensile strength with increased cold rolling reduction, while also decreasing the
ductility. The precipitation of secondary strengthening phases also contributed to
increased strength, albeit to a lesser extent as degree of deformation increased.
The microstructure revealed a transformation from an equiaxed, well defined grain
structure with a significant amount of deformation twins, to a visibly deformed
grain structure characterized by elongated grains and deformation bands. Further,
the microstructure showed indication of texture formation with a preferred grain
orientation and intergranular slight variations in orientation. | |
