Tesis doctoral de Jorge Luis Bris Cabrera
In recent years, manufacturing of sintered components has shown an important growth. Competitiveness of powder metallurgy demands to produce higher performance components at low costs. Reducing internal porosity is a well known method to improve the mechanical properties of sintered steels. In this doctoral thesis, the mechanical behaviour of a high-density sintered steel (fe-4,0ni-1,5cu-0,5mo-0,5c) is studied. Several processing routes have been used in order to attain different density levels (from 7,2 to 7,5 g/cm3), including: cold compaction, warm compaction, single and double pressing, sintering at low- and high-temperatures, and secondary operations. The results achieved shows that density of a pm part can be controlled by processing conditions. Highest density levels are obtained combining warm compaction with double pressing-double sintering. The mechanical properties evaluated increased linearly with sintered density, regardless of the processing route followed for achieving a given density level. This correlation can be rationalized taking into account that the mechanical resistance in pm steels is influenced not only by the reduction in load-bearing area produced by the presence of pores, but also by stress concentration and localized plastic deformation at sintering necks. In this context, it is found that smaller and rounder pores and larger pore-spacing improve the mechanical performance. The localized plastic deformation observed on the fracture surfaces of the materials investigated explain the positive correlation between yield stress and fracture toughness; opposite to the relationship exhibited by wrought materials. This performance may be highlighted as a structural advantage once the accompanying improvement in tensile properties by density is accounted. The study of the mechanical behaviour under cyclic loading allows to state that fatigue failure starts with nucleation of microcracks at larger and more irregular pores, where stress concentrati
Datos académicos de la tesis doctoral «Comportamiento mecanico de aceros sinterizados de alta densidad«
- Título de la tesis: Comportamiento mecanico de aceros sinterizados de alta densidad
- Autor: Jorge Luis Bris Cabrera
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 08/03/2007
Dirección y tribunal
- Director de la tesis
- Luis Llanes Pitarch
- Tribunal
- Presidente del tribunal: marcos Juan Anglada gomila
- Elena Gordo orderiz (vocal)
- vicente Amigó borrás (vocal)
- José Antonio Calero martínez (vocal)