Name: DAVI DE CARLI
Publication date: 27/02/2023
Advisor:
Name |
Role |
|---|---|
| MARCELO BERTOLETE CARNEIRO | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| MARCELO BERTOLETE CARNEIRO | Advisor * |
Summary: Functionally Graded Material (FGM) is made from two or more materials with distinct properties in a gradient form, allowing the change of properties along the volume. The FGM manufacturing process is an important research theme, in which powder metallurgy (PM) highlights owing to a wide range of materials, microstructure, and shape control. Pulsed Electric Current Sintering (PECS) is a modern and efficient sintering technique. The aim is to design a ceramic FGM, manufactured by PM using PECS as sintering technique; in addition to characterizing the stepped gradient microstructure, density, hardness and fracture toughness. Ultrafine α-Al2O3 powder, nanopowder 3Y-ZrO2 and TiC, and fine WC-Co powder were the materials used to manufacture the FGM. A one-dimensional thermomechanical model was used to predict residual stress in the FGM. The samples were sintered at 1425ºC with a dwell time of 7 minutes, uniaxial pressure of 50 MPa, and vacuum atmosphere. The microstructure was characterized by optical and scanning electron microscopy after metallographic preparation. The density evaluation was done on a precision scale using Archimedes principle, and the theoretical density was obtained from the inverse rule of mixtures. Vickers macroindentation hardness test and fracture toughness by indentation method were carried out. The residual stress prediction indicated tensile stress in rich ceramic layers; however, below the fracture strength. Cracks due to residual stress along the microstructure were not observed in the microscopic analysis. Different volume fractions of the constituents evidenced the stepped gradient. The average value of relative density was 98.68%, meaning 1.32% of porosity. A change in hardness number was observed along the gradient, as well as in fracture toughness.
Key words: Functionally graded material, ceramic, density, hardness, fracture toughness
