Abstract
The present work concerns the influence of surface (machined, as-built) on the fatigue resistance of AlSi10Mg produced by a powder-bed laser process. The competition between defects and surface roughness is assessed by using Kitagawa-type diagrams. Samples are printed along three directions: 0°, 45° and 90°. After axial fatigue tests with a load ratio of R = −1, all the fracture surfaces are carefully analysed. The initiation sites can be (i) a defect, (ii) the surface roughness, (iii) the surface ripple. The results indicate that ground surfaces lead to the same fatigue life as as-built surfaces. It is also shown that T6 treatment improves the fatigue resistance. However, when specimen surfaces are as-built or ground, it is difficult to correlate the fatigue results with ‘isolated defect size analysis’ neither roughness parameter for an as-built surface. Therefore, microstructure, residual stresses or multiple initiation should be further analysed to understand the results.
Highlights
Additive manufacturing processes are innovative and disruptive technologies, because they offer attractive prospects in the manufacturing of parts with a complex geometry while reducing the number of fabrication steps and the quantity of raw material
This study is dedicated to the characterisation and analysis of the fatigue strength of as-built and grounded surfaces in an ALM AlSi10Mg alloy
- T6 treatment improves the fatigue properties for as-built surfaces, to the results obtained on machined surfaces
Summary
Additive manufacturing processes are innovative and disruptive technologies, because they offer attractive prospects in the manufacturing of parts with a complex geometry while reducing the number of fabrication steps and the quantity of raw material. Regarding the tensile or fatigue resistance, the impact of conventional T6 heat treatment has been assessed This heat treatment homogenises the melt-pools and the dendritic structure by producing silicon wafers randomly distributed in the matrix [14,15,16,17,18]. Several works carried out on specimens machined from bars revealed anisotropy effects in tensile properties [9,12,14,19]. This anisotropy is related to the building direction [20], which itself induces a pronounced microstructural anisotropy. By modifying the microstructure through a T6 treatment, the effects of anisotropy on tensile properties are limited and improvement both in the yield stress and in the elongation at failure can be noted [14]
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