Mechanical Behavior Of Aluminum Alloys Research Articles

Mechanical Behaviour of Aluminium Alloy Reinforced with Sic/Fly Ash/Basalt Composite for Brake Rotor

Gray cast iron is the most commonly used material in automobile brake rotors. It generates heat easily during braking which affects its mechanical properties and the Coefficient of friction varies depending on the type of material used for the brake rotor. Aluminium (Al) based metal matrix composite can be an efficient and effective braking material compared to cast iron and matrix alloy. In the present investigation, Al6082 composites were fabricated by stir casting method by varying weight percentage of reinforcements for Sample1 (Al 90% + SiC 10%), Sample 2 (Al 90% + SiC 5% + fly ash 5%) and Sample 3 (Al 90% + SiC 5% + basalt 5%). Chemical compositions, micro hardness, wear test and tensile test were performed to study the mechanical behavior of all the test specimens. The surface morphology was studied using microscopic inspection to indicate the distribution of reinforcement particles and bonding between the matrixes. Composites containing hard oxides (like SiC) are preferred for high wear resistance along with increased hardness and high temperature oxidation resistance. The result reveals that wear rates of the composite materials is lower than that of the matrix alloy and friction coefficient was minimum. Also, it improves the micro hardness and tensile strength. The addition of fly ash and basalt decreases the wear and it acquired density almost three times lower than that of gray cast iron. In this investigation, the alternate materials for automobile brake rotors with Al reinforced composites were studied.

Aspects onmodeling the mechanical behavior of aluminum alloys with differentheat treatments

Aspects onmodeling the mechanical behavior of aluminum alloys with differentheat treatments

Overview of aluminum alloy mechanical properties during and after fires

AbstractAluminum alloys are increasingly being used in a broad spectrum of load-bearing applications such as lightweight structures, light rail, bridge decks, marine crafts, and off-shore platforms. A major concern in the design of land-based and marine aluminum structures is fire safety, at least in part due to mechanical property reduction at temperatures significantly lower than that for steel. A substantial concern also exists regarding the integrity and stability of an aluminum structure following a fire; however, little research has been reported on this topic. This paper provides a broad overview of the mechanical behavior of aluminum alloys both during and following fire. The two aluminum alloys discussed in this work, 5083-H116 and 6061-T651, were selected due to their prevalence as lightweight structural alloys and their differing strengthening mechanisms (5083 – strain hardened, 6061 – precipitation hardened). The high temperature quasi-static mechanical and creep behavior are discussed. A creep model is presented to predict the secondary and tertiary creep strains followed by creep rupture. The residual mechanical behavior following fire (with and without applied stress) is elucidated in terms of the governing kinetically-dependent microstructural mechanisms. A review is provided on modeling techniques for residual mechanical behavior following fire including empirical relations, physically-based constitutive models, and finite element implementations. The principal objective is to provide a comprehensive description of select aluminum alloys, 5083-H116 and 6061-T651, to aid design and analysis of aluminum structures during and after fire.

Cryogenic mechanical behavior of 5000- and 6000-series aluminum alloys: Issues on application to offshore plants

The mechanical behavior of aluminum alloys was investigated in terms of four aspects: temperature, strain rate, material type, and fracture shape. The candidate materials were 5000- and 6000-series alloys. The material characteristics were investigated and summarized as a function of low temperature (110–293K) and quasi-static strain rate (10−4 and 10−2s−1). The results confirmed that the strength and ductility of aluminum alloys improved with a decrease in the temperature. The aluminum alloys showed a strain rate effect only in terms of the ductility of the 5000-series alloys. In addition, fractography analyses were performed on the fracture specimens to explain the material behavior at cryogenic temperatures.

Fatigue crack initiation life prediction for aluminium alloy 7075 using crystal plasticity finite element simulations

An experimentally-validated approach for predicting fatigue crack initiation life of polycrystalline metals is developed based on crystal plasticity finite element (CPFE) simulations. In this approach, the microstructure used in the simulations possesses statistically the same grain size and crystallographic orientations as those obtained from electron back-scatter diffraction experiments. A backstress model is incorporated into the CP constitutive model to describe the mechanical behaviour of aluminium alloy (AA) 7075 under cyclic loading. The key variables of the prediction model, the energy efficiency factor and plastic strain energy density, are calibrated using a fatigue test on a round-notched AA7075 specimen at room temperature. The proposed approach is then validated by using another fatigue test to predict 69.1–87.3% of the experimentally measured fatigue crack initiation life. The effects of the microstructure and texture on the energy efficiency factor and fatigue life prediction are quantitatively determined. It is shown that for a given range of energy efficiency factors a similar range of life prediction is obtained. Since the proposed approach considers the heterogeneity of the microstructure, it can well capture the grain scale deformation localisation and therefore improve the precision of fatigue life prediction.

Finite element simulation of nanoindentation tests using a macroscopic computational model

The aim of this work was to develop a numerical procedure to simulate nanoindentation tests using a macroscopic computational model. Both theoretical and numerical aspects of the proposed methodology, based on the coupling of isotropic elasticity and anisotropic plasticity described with the quadratic criterion of Hill are presented to model this behaviour. The anisotropic plastic behaviour accounts for the mixed nonlinear hardening (isotropic and kinematic) under large plastic deformation. Nanoindentation tests were simulated to analyse the nonlinear mechanical behaviour of aluminium alloy. The predicted results of the finite element (FE) modelling are in good agreement with the experimental data, thereby confirming the accuracy level of the suggested FE method of analysis. The effects of some technological and mechanical parameters known to have an influence during the nanoindentation tests were also investigated.

Residual mechanical properties of aluminum alloys AA5083-H116 and AA6061-T651 after fire

Aluminum alloys are increasingly being used in a broad spectrum of load-bearing applications such as light rail and marine crafts. Post-fire evaluation of structural integrity and assessment of the need for structural member replacement requires understanding of the residual (post-fire) mechanical behavior. Aluminum alloys are strengthened by either strain hardening (cold/hot rolling) or precipitation hardening (heat treatment). Prevalent structural alloys strengthened by each method were investigated in this research: AA5083-H116 (strain hardened) and AA6061-T651 (precipitation hardened). An experimental study was conducted to quantify the residual mechanical behavior of aluminum alloys following a fire exposure. Heating of the aluminum alloys results in evolution of material microstructure, which governs mechanical behavior. Microstructural evolution can be predicted as a kinetically-driven process. As a result, the effects of exposure temperature and heating rate on the residual mechanical properties were quantified. Monotonic, uniaxial tension tests were performed to measure the residual stress–strain relations, which were used to quantify the residual Young’s modulus, yield strength, ultimate strength, and work hardening behavior. AA6061-T651 was determined to have a more significant decrease in strength after fire exposure as compared to AA5083-H116. The heating rate affected the temperatures at which property degradation initiated as well as the residual property magnitude at a given temperature. This is most prevalent in temperature regions with significant microstructural changes, such as recrystallization and precipitate growth. The knowledge elucidated in this study was used to develop empirical evolution models to estimate residual yield strength after linear (ramp) heating and isothermal exposure. Utilizing these models, residual yield strength evolution after realistic fire exposure, which includes combinations of linear and isothermal heating, may be estimated and understood.

Experimental study of macro–micro dynamic behaviors of 5A0X aluminum alloys in high velocity deformation

Investigation of macro–micro dynamic mechanical behavior of aluminum alloys is crucial to understand and model high velocity forming processes, e.g. the electromagnetic forming. Therefore, this work presents the experimental investigation of the macro–micro dynamic deformation behavior and related mechanisms of 5A0X alloys. With increasing strain rate, notable hardening and serrated flow curves are observed for both 5A06 and 5A02 alloys; the flow softening ratio increases from 10.59% to 15.56% for 5A06 alloy, while increasing up to 34.55% at a strain rate of 3000s−1 for 5A02 alloy. High velocity deformation enhances the ductility of both the alloys via slowing down the neck development rather than suspending the onset of necking. Comparative study in dynamic tensile/compressive behavior of 5A06 alloy indicates a similar hardening rule in these two loading conditions, however, more obvious softening is found in tension than that in compression. The difference can be attributed to the different microstructure-related characteristics, namely, the diffuse necking related to void evolution in tension and the adiabatic shear bands (ASB) in compression. In addition, a mathematical model is used in this work to corroborate the occurrence of ASBs and to predict the half width of ASBs, which is proved reliable by experiments.

Influence of strain state in mechanical behaviour of aluminium alloys using the Small Punch Test

The Small Punch Test (SPT) basically consists of deforming a miniature specimen, whose edges are firmly gripped by a die, using a high strength punch. This test was developed in the eighties and has since been used successfully on numerous occasions in those cases where there is not sufficient material to carry out standard tests to obtain the mechanical properties of materials. In recent years, it has been used successfully to determine the yield strength evolution in any area of stamped aluminium alloy components.These stamped components are subject to different kinds of plastic deformation during the stamping process. The main objective of this paper is to analyze the influence that the type of deformation reached during the stamping process has on the mechanical behaviour of the material. Furthermore, for each kind of strain, the yield load in the SPT will be related to yield strength to provide a unique valid expression to evaluate the hardening of the material.

Study of the structure and properties of a wrought Al–Mg–Mn aluminum alloy on a Gleeble 3800 simulator designed for physical modeling of thermomechanical processes

The mechanical behavior of aluminum alloy 5454, belonging to the system Al‐Mg‐Mn, is studied during hot plastic deformation on a Gleeble 3800 simulator designed for physical modeling of thermomechanical processes. The study was conducted under different temperature-rate conditions. Examination of the structure of the hot-deformed specimens showed that dynamic recrystallization is impeded in the alloy. The substructure obtained after deformation at 400°C consists mainly of equiaxed subgrains with dimensions of 1‐2 µm, the exact size depending on the rate of deformation. A mathematical model that was constructed to relate the flow stress of the given alloy to the rate, temperature, and degree of deformation can be used for finite-element calculation of the properties of different sections of products of complex shape that are made of this alloy by various methods of hot plastic deformation.

Mechanical Behavior of Aluminum Alloys During Small Punch Test

Abstract Small Punch Tests (SPTs) were conducted in order to determine material properties and understand their mechanical behavior. Equations were derived to calculate the yield strength, ultimate tensile strength, modulus of elasticity, and hardness of five aluminum alloys. A greater understanding of the mechanisms of the SPT and how specimens behave during testing is also discussed. It was found that the 2024-T3 and 7075-T651 aluminum alloys were shown to have the highest maximum small punch force before failure. The relationship between the SPT parameters and the yield strength, tensile strength, elastic modulus, and hardness is shown to be linear. The empirical equation developed here is suitable for aluminum alloys.

Further Development of Ideas of G.V. Akimov on the Surface Oxide Films and Their Effect on the Corrosion and Mechanical Behavior of Aluminum Alloys

The importance of oxide films and their perfection in extending the application of aluminum alloys are shown. The composition and structure of oxide films formed by microarc oxidation on aluminum alloys of different alloying systems and production methods are studied. The dependence of the oxide coating properties on the parameters of microarc oxidation are found. The results obtained are discussed in terms of the existing concepts of microarc oxidation.

On the mechanical behavior of aluminum alloys reinforced by long or short alumina fibers or SiC whiskers

This study was initiated to examine the dispersion of longitudinal and transverse waves in metal matrix composites in order to obtain the dynamic elastic modulus and to evaluate various models for predicting the composite's macroscopic elastic constants from the properties of its constituents. The materials chosen for this investigation were alumina continuous fibers on the one hand and alumina and SiC short fibers on the other hand, all embedded in an aluminum alloy matrix. In addition, some indications have been obtained experimentally for the acoustoelastic effect in the composite.

Influence of nonequilibrium second-phase particles formed during solidification upon the mechanical behavior of an aluminum alloy

The mechanical behavior of a wrought high strength aluminum alloy is examined as a function of the concentration of second-phase microconstituents. These second-phase particles are located in grain boundaries and interdendritic sites. Their concentration was varied by thermal-mechanical processing. In the areas of strengths, ductility, crack toughness, fatigue, and stress corrosion cracking, empirical results are presented and discussed. Observations are made on changes in the anisotropic character of this category of material with lower concentrations of second phases.