•Stress gradients and inhomogeneous porosity distribution control the fatigue behavior,•Murakami parameter is pertinent for estimating the criticality of porosity networks,•It is likely that the ...atmosphere within the casting porosity affects the fatigue behavior,•Good correlation is seen between El Haddad’s parameter and microstructurally based parameters.
In order to expand the number of possible applications of High Pressure Die Cast (HPDC) components using the AlSi9Cu3 alloy, the automotive industry is giving greater attention to the fatigue design of components produce by this process-material combination. The process is well known for introducing a heterogeneous distribution of casting defects. This study explores the impact of the heterogeneous porosity distribution and stress gradients on the high cycle fatigue behavior of HPDC AlSi9Cu3 components. Fatigue tests under fully-reversed tension–compression and fully-reversed bending loads are used to investigate the influence of porosity and stress gradients on the fatigue behavior, by machining different specimen thicknesses. The results demonstrate that stress gradients and the heterogeneous porosity distribution determine the material’s fatigue response, including both the fatigue strength and crack initiation mechanisms. The Murakami parameter and local stress level at the critical defect make it possible to interpret the gradient effects. The nature of the entrapped gas in internal defects may influence the in-bulk crack propagation behavior. The comparison of fracture mechanics models (El Haddad, Murakami, Kitagawa-Takahashi) make it possible to highlight the link between the El Haddad’s parameter to parameters that are more microstructurally based.
An orthogonal test was conducted to investigate the influence of technical parameters of squeeze casting on the strength and ductility of AlSi9Cu3 alloys. The experimental results showed that when ...the forming pressure was higher than 65 MPa, the strength (σb) of AlSi9Cu3 alloys decreased with the forming pressure and pouring temperature increasing, whereas σb increased with the increase of filling velocity and mould preheating temperature. The ductility (δ) by alloy was improved by increasing the forming pressure and filling velocity, but decreased with pouring temperature increasing. When the mould preheating temperature increased, the ductility increased first, and then decreased. Under the optimized parameters of pouring temperature 730 °C, forming pressure 75 MPa, filling velocity 0.50 m/s, and mould preheating temperature 220 °C, the tensile strength, elongation, and hardness of AlSi9Cu3 alloys obtained in squeeze casting were improved by 16.7%, 9.1%, and 10.1%, respectively, as compared with those of sand castings.
In this paper, the preparation, microstructures and mechanical properties of in-situ (TiB2 + ZrB2)/AlSi9Cu3 composites are investigated by X-Ray diffraction (XRD), optical microscope (OM), scanning ...electronic microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM) and tensile testing. The composites are fabricated from Al–K2TiF6–K2ZrF6–KBF4 system via melt in-situ reaction technology. The results reveal that the morphology of TiB2 and ZrB2 particles is presented in rectangular and nearly hexagonal, and the size of 20–100 nm in the synthesized composites. In addition, the particles are agglomerated as many of “Reinforced Group”, which are distributed along the crystal boundary of the matrix. The silicon phase and secondary dendrite arm spacing of AlSi9Cu3 alloy are obviously changed by the introduction of in-situ particles. The morphology of the silicon phase is presented in rod-shape or needle-shape with the size of about 3–10 μm. The particles affect the formation of dendrites and the size of the secondary dendrite arm spacing is 9.8–20 μm, while it seems to not affect the morphology of the CuAl2 phase. Tensile testing results show that the tensile strength and elongation clearly increase with the introduction of in-situ particles. Moreover, the tensile strength and elongation reach 265 MPa and 14.8% respectively, with the best reaction time (30 min) and mass fraction of reactants (20wt.%). The mechanical stirring also significantly affected the particles dispersion in the composites.
•The (TiB2 + ZrB2)/AlSi9Cu3 matrix composite is successfully fabricated.•Effect of reaction time and reactants mass fraction on the composites is studied.•Effect of mechanical stirring on the in situ composites is studied.•The reinforcing mechanism of the in situ composites is discussed.
•E–N curves and their scatter were estimated by a two-parametric Weibul PDF.•Conditional PDF of load cycles to failure depends on strain amplitude.•Parameters of PDF were estimated by evolutionary ...algorithms (GA and DASA).•The estimated PDF models well the E–N curves and their scatter.
We present an approach for estimating E–N curves and their scatter. The scatter of a number of load cycles to failure at an arbitrary amplitude-strain level is modelled using a two-parametric Weibull distribution with the constant shape parameter β and the scale parameter η dependent on the strain amplitude by the Coffin–Manson equation. In this way the E–N curve and its scatter can be described using five parameters: the four parameters of the Coffin–Manson equation for the scale parameter of the Weibull distribution and the shape parameter of the Weibull distribution. The objective was to estimate these five parameters, which are generally unknown (since the data from the literature are manly known only for the median E–N curves), on the basis of the known fatigue-life data to obtain not only the trend of the E–N curve, but also its scatter. In order to estimate these parameters on the basis of the fatigue-life data, two evolutionary algorithms were applied: a real-valued genetic algorithm (GA) and the differential ant-stigmergy algorithm (DASA). In the article a mathematical background of the approach is presented and applied to 27 test cases of simulated fatigue-life data and one real case of experimentally obtained fatigue-life data. The results are analysed and discussed.
Most of the published research work related to the fatigue life of porous, high-pressure, die-cast structures is limited to a consideration of individual isolated pores. The focus of this article is ...on calculating the fatigue life of high-pressure, die-cast, AlSi9Cu3 parts with many clustered macro pores. The core of the presented methodology is a geometric parameterisation of the pores using a vector-segmentation technique. The input for the vector segmentation is a μ-CT scan of the porous material. After the pores are localised, they are parameterised as 3D ellipsoids with the corresponding orientations in the Euclidian space. The extracted ellipsoids together with the outer contour are then used to build a finite-element mesh of the porous structure. The stress–strain distribution is calculated using Abaqus and the fatigue life is predicted using SIMULIA fe-safe. The numerical results are compared to the experimentally determined fatigue lives to prove the applicability of the proposed approach. The outcome of this research is a usable tool for estimating the limiting quantity of a structure’s porosity that still allows for the functional performance and required durability of a product.
This study investigates the influence of cutting parameters on longitudinal turning of high Silicon cast aluminium alloy AlSi9Cu3 using PCD tools with and without chip breaker geometry. In order to ...build the 3D numerical model, the experimental and predicted cutting forces were used for inverse calibration of the Johnson–Cook material model which was implemented in DEFORMTM finite element software. A sensitivity analysis has been performed in order to obtain an acceptable prediction of the machining parameters such as chip geometry and cutting forces as well as to understand the influence of friction and mesh size effects in the predicted results. Results have shown a satisfactory correlation between experimental turning data and numerical estimates based on assumptions that have been taken for the material behaviour.
In this paper we studied the influence of heat treatments on properties of AlSi9Cu3(Fe) nondendritic cast alloy. Solution heat treatment, six hours at 520 °C, while making the grains more spherical ...modifies corrosion morphology into intergranular corrosion and corrosion surrounding spherical particles in 3 % NaCl solution. Past solution treatment, quenching at 520 °C after one hour with two weeks of natural aging transform the shape of grains into equiaxes form. Two weeks of natural aging and 30 minutes of aging at 150, 200, 250 °C after solution treatment and quenching give birth to the "Chinese script" form of the Al15(MnFe)3Si intermetallic particles. The prolongation of the duration period of aging to one hour at 200 °C is sufficient to transform the morphology of corrosion into located corrosion by pitting, and a longer aging cancels the "Chinese script" form. DOI: http://dx.doi.org/10.5755/j01.ms.19.3.1397
The experimental and analytical approaches were taken to investigate the non-dendritic microstructure formation and evolution of AlSi9Cu3 alloy during rheocasting. The results show that the globular ...primary
a(Al) particles free of entrapped eutectic form after rheocasting for 3 s, and could be morphologically stabilized during subsequent growth. The fine and globular particles underwent a coarsening process under quiescently continuous cooling in which the particle density decreases, the solid fraction increases, the average particle size increases with the increase of solidification time at a rate that closely followed the classical Ostwald ripening.
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