A design-centered approach in developing Al-Si-based light-weight alloys with enhanced fatigue life and strength

Abstract

Material heterogeneities and discontinuities such as porosity, second phase particles, and other defects at meso/micro/nano scales, determine fatigue life, strength, and fracture behavior of aluminum castings. In order to achieve better performance of these alloys, a design-centered computeraided renovative approach is proposed. Here, the term "design-centered" is used to distinguish the new approach from the traditional trial-and-error design approach by formulating a clear objective, offering a scientific foundation, and developing a computer-aided effective tool for the alloy development. A criterion for tailoring "child" microstructure, obtained by "parent" microstructure through statistical correlation, is proposed for the fatigue design at the initial stage. A dislocations pileup model has been developed. This dislocation model, combined with an optimization analysis, provides an analytical-based solution on a small scale for silicon particles and dendrite cells to enhance both fatigue performance and strength for pore-controlled castings. It can also be used to further tailor microstructures. In addition, a conceptual damage sensitivity map for fatigue life design is proposed. In this map there are critical pore sizes, above which fatigue life is controlled by pores; otherwise it is controlled by other mechanisms such as silicon particles and dendrite cells. In the latter case, the proposed criteria and the dislocation model are the foundations of a guideline in the design-centered approach to maximize both the fatigue life and strength of Al-Si-based light-weight alloy.

Enhancing Fatigue Properties of Nanostructured Metals and Alloys

“…The phenomenology for extending nanoscale and microscale computations of deformation fields to predict fatigue life parallels the work of Fan et al [24], but with adaptations to address nanoscale phenomena. The total number of fatigue cycles to failure at a constant applied cyclic stress during…”

“…The premise of this work is that microstructural design-centered approaches to fatigue life prediction that have been applied successfully at the microscale [24] can be extended to the nanoscale by combining currently available experimental and computational techniques. Three elements must be combined: 1) experimental measurement of nanoscale defect densities, sizes, and shapes, 2) spatially discrete numerical analysis of deformation fields surrounding these defects, and 3) a correlation between the local stress and strain fields and fatigue crack incubation and growth.…”

Influence of Cooling Rate on Fatigue Behaviour of Eutectic Al-Si (A413) Alloy Casting

“…Owing to the complex microstructure of cast aluminum alloys, the fatigue life manifest high orders of variation in the high-cycle fatigue tenure, in which the fatigue life is sensitive to microstructures [5]. The morphologies of secondary phase particles, the presence of micro porosity and other defects, determine fatigue life, strength, and fracture behavior of aluminum castings [6,7]. Hence, refining the microstructure is a typical practice to enhance the mechanical properties of a casting.…”

Microstructural Inclusion Influence on Fatigue of a Cast A356 Aluminum Alloy

“…The DCS is proportional to pore size, as Major [12] observed. Hence, pore size, [15][16][17] porosity level, [17][18][19][20] and casting defects [21] have also been a focus of fatigue failure. However, NNDs must also be considered along with second-phase particles and oxides as well.…”