Study of multidirectional forging and annealing on copper.
Lim, Zi Xin.
Date of Issue2009
School of Materials Science and Engineering
The use of macroforming technology to produce microproducts has problem such as poor mechanical properties and rough surface due to relatively large grains and fewer grain boundaries. Hence, there is a need to achieve grain refinement in materials in order to have better properties and yet is cost-effective for mass production. Severe plastic deformation is gaining attention due to the simplicity of tools and procedures in producing ultrafine grains. It is also a cost-effective method due to the ability of bulk production. Multi directional forging (MDF) is a method of severe plastic deformation in which large amount of plastic strains is stored in the material with repeated cycles of MDF without significant changes in dimensions. In this project, MDF was done on copper samples to obtain grain refinement. The results showed that after MDF, there were a reduction in grain size and an enhancement in hardness. This is mainly due to formation of deformation bands such as microshear bands. This resulted in fragmentation of grain with high angle boundaries, leading to formation of small grains. The high hardness of copper is due to strain hardening and increased grain boundaries due to small grains. Thermal annealing of the MDFed copper samples were also done at different annealing temperatures. The results showed that annealing was accompanied by a drop in hardness and an increase in grain size and at higher temperature, hardness is reduced at a higher rate. This is mainly due to higher diffusivity of atoms, which leads to faster recrystallisation and grain growth in the samples.
Final Year Project (FYP)
Nanyang Technological University