microstructure and fatigue performance of slm fabricated ti6al4v alloy after different stress relief heat treatments

Abstract The main interest in Additive Manufacturing (AM) technology relates to its ability to produce complex components with relatively reduced weight that are difficult to produce or cannot be produced by other conventional technologies. Selective laser melting (SLM) is extensively used, as one of the AM technologies to fabricate metallic parts. This advanced method allows to produce various parts with complex geometries with high three-dimensional (3D) accuracy from fusion powders in a layer-by-layer style. Ti6Al4V alloy is a widely used material for structural applications in aerospace and biomedical due to high specific fatigue strength. SLM processing makes this alloy attractive when weight reduction is a design objective. The SLM Ti6Al4V microstructure is influenced by process parameters and build orientation. The localized high energy input during very short interaction times leads to the formation of very fine structures and to the generation of internal stresses. Therefore, the SLM parts are heat treated to decrease or completely remove residual stresses. The present study aims at evaluating the effect of stress-relief heat treatments on the microstructure, the mechanical properties and the fatigue performance of SLM Ti6Al4V alloy. Ti6Al4V alloy specimens were manufactured according to the SLM process with an EOS M290 system. Post fabrications heat treatments at different temperatures (i.e. 740˚C vs. 900˚C) resulted in different structure and mechanical properties that were identified and measured. Fatigue testing of specimens with as-built surfaces was performed at room temperature on modified Schenk-type fatigue testing machine applying a pulsating plane bending (load cycle ratio R = 0) to the specimens at a frequency f = 15 Hz

Fatigue Strength of Nodular Cast Iron with Different Surface Conditions under Bending Loading

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Fatigue Strength of Nodular Cast Iron with Different Surface Conditions under Bending Loading

The aim of this study is to evaluate the effects of surface conditions on the fatigue life of nodular cast iron under cyclic plane bending where the maximum stress is reached at the surface of interest. In order to evaluate the effect of surface conditions, fatigue tests were carried out on five sets of specimens with different surfaces. The surface conditions were as-cast, sand blasted, fine ground, nitrided and carbonitrided. The results show differences in fatigue strength, which are associated with the surface conditions. The characteristics of the surface layers in the different test specimens were examined by metallography. The fracture surfaces were fractographically analyzed to find places of fatigue crack initiation and to explain different fatigue life

Influence of the Heat Treatment on the Microstructure, Mechanical Properties and Fatigue Behavior of Additively Manufactured Ti6Al4V Alloy

This contribution deals with the selective laser melting (SLM), which is one of the additive manufacturing (AM) technologies enabling the production of complex parts from metal powder, layer-by-layer wise. This technology uses laser as source of energy to melt a powder to compact state. Properties of final products can be significantly influenced by the process parameters and post-fabricated heat treatments. The purpose of this study is to determine the effect of a heat treatment on properties of the Ti6Al4V alloy specimens manufactured by Eosint M280 machine by the SLM. Three sets of specimens, treated at different temperatures (730 ˚C, 900 ˚C, 1200 ˚C), resulting in a different structure, associated mechanical and fatigue properties, were investigated

Influence of Build Orientation on Surface Roughness and Fatigue Life of the Al2024-RAM2 Alloy Produced by Laser Powder Bed Fusion (L-PBF)

Additive manufacturing of high strength Al alloys brings problems with hot cracking during rapid solidification. One of the ways to solve this challenge is technology developed by the Elementum 3D company. The way consists of inoculation by ceramic nanoparticles using RAM technology. When applying the L-PBF method, a very fine equiaxed microstructure with exceptional properties and without cracks is created. This paper offers the results and discussion of the microstructure, surface roughness and fatigue life of the high-strength Al2024-RAM2 alloy made from a gas atomized powder with an additive of 2 wt.% ceramic nanoparticles on the base of Ti. The specimens for fatigue tests were produced in different orientations relative to the building platform and left in the as-built conditions with different surface quality (roughness). The specimens were T6 heat-treated. The treatment caused a coarsening of a part of the fine grains. After T6 heat treatment, the hardness increased significantly, which occurred by precipitation hardening. Fatigue tests of specimens with different build orientation were performed in plane bending and the experimentally determined fatigue life was discussed in terms of surface roughness and material microstructure