Evolution of microstructure and mechanical properties during annealing of cold-rolled AA8011 alloy

The evolution of recrystallized microstructure of cold-rolled aluminium alloy AA8011 is investigated with the help of optical metallography, orientation imaging microscopy (OIM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), electrical resistivity and microhardness measurements at different annealing conditions. Tensile testing of the isochronally annealed specimens is performed to examine the effect of annealing temperature and microstructure on mechanical properties. Precipitates affect the grain growth behaviour and texture evolution. Normal grain growth takes place prior to abnormal grain growth. A wide range of grain size distribution and a combination of cube, rolling and random texture is observed at complete recrystallized condition. Our results provide not only new insight into aluminium packaging materials (i.e., foils, cans, and air conditioning ducts) but also a platform to better understand the recrystallization of a wide range of related alloys

A study of precipitation and recrystallization behaviour of aluminium alloy AA1235

The recrystallization behaviour of 92% cold rolled commercial pure aluminium has been studied. Annealing was done at different conditions to evaluate the effect of recrystallization temperature and time on the microstructure and texture of the alloy along with a study of subsequent precipitation. Variation of orientation between grains has been studied by the orientation imaging microscopy (OIM). During precipitation, cube component {001} has dropped and rolling texture component {112} has increased comparatively. Recrystallization texture is the combination of cube, rolling and random texture. However, during grain growth strong cube grains have formed. A significant number of dislocations are present during grain growth owing to the pinning effect of Al3Fe particles

Microstructures and tensile properties of commercial purity aluminium alloy AA1235 under different annealing conditions

Microstructures, hardness, tensile properties and texture of cold-rolled AA1235 alloy are investigated under different annealing conditions. Precipitation of Al3Fe particles occurs during annealing of the alloy. These precipitates largely affect the microstructural behaviour, tensile properties and texture of the alloy. After complete recrystallization no change in mechanical properties is observed upon further annealing

A novel rate based methodology for creep fatigue life estimation of superalloys

In this present work, we present an accumulated inelastic strain rate based methodology to predict creep fatigue life of two different superalloys i.e. Haynes 282 and IN 718. The evolution of differential strain rate during creep and fatigue respectively motivated the present work. As creep is the rate controlling damage process in creep fatigue interaction, present mean strain rate based approach considers creep strain rate as a kinetic variable controlling the process. The other variable considered for this approach is accumulative cyclic strain during Creep-fatigue interaction. Our prediction method is purely based upon a relative accumulation rate of creep and fatigue strain. This method correlates the creep fatigue life with rate of interaction in strain-controlled regions successfully from the data of creep fatigue tests on those superalloys at two temperatures, 650 °C and 760 °C. We found suitable microstructure sensitive constants in a lifing model

Processing-microstructure-yield strength correlation in a near β Ti alloy,Ti–5Al–5Mo–5V–3Cr

A combined set of thermo-mechanical steps recommended for high strength β Ti alloy are homogenization,deformation, recrystallization,annealing and ageing steps in sequence.Recrystallization carried out above or below β transus temperature generates either β annealed(lath type morphology of α) or bimodal (lath+globular morphology of α) microstructure.Through variations in heat treatment parameters at these processing steps,wide ranges of length scales of features have been generated in both types of microstructures in a near β Ti alloy,Ti–5Al–5Mo–5V–3Cr(Ti-5553).0.2%Yield strength(YS)has been correlated to various microstructural features and associated heat treatment parameters.Relative importance of microstructural features in influencing YS has been identified.Process parameters at different steps have been identified and recommended for attaining different levels of YS for this near β Ti alloy

Ultrasonic quantification of high temperature cyclic damage in an advanced nickel based superalloy

Present paper discusses about a new methodology to quantify cyclic damage through ultrasonic measurement. Based on experimental results, correlations have been made between damage accumulated inside the material due to strain excursions and corresponding ultrasonic parameters. It has been proposed that based on the existing correlation between attenuation coefficient and number of cycles to failure, fatigue failure characteristics can be partitioned into two regimes (a) failures due to early nucleation and rapid propagation of cracks and (b) failures due to delayed propagation and crack coalescence. Plastic strain accumulation and surface crack density have been chosen as two physical parameters directly influencing attenuation coefficient and it has been observed that with increasing plastic strain accumulation, ultrasonic attenuation increases. Between two primary echoes of ultrasonic spectra, some secondary defect echoes have been found. A damage descriptor has been introduced by taking difference between the bandwidth of defect echo and badman echo normalized by overall amplitude frequency distributions of backwall echo. It has been found to bear sensitivity towards surface crack density. This quantitative estimation differentiates between the classical descriptions of damage due to dislocation mediated plasticity, micro crack generation and coalescence. (C) 2014 Elsevier B.V. All rights reserved

Ultrasonic quantification of high temperature cyclic damage in an advanced nickel based superalloy

Present paper discusses about a new methodology to quantify cyclic damage through ultrasonic measurement. Based on experimental results, correlations have been made between damage accumulated inside the material due to strain excursions and corresponding ultrasonic parameters. It has been proposed that based on the existing correlation between attenuation coefficient and number of cycles to failure, fatigue failure characteristics can be partitioned into two regimes (a) failures due to early nucleation and rapid propagation of cracks and (b) failures due to delayed propagation and crack coalescence. Plastic strain accumulation and surface crack density have been chosen as two physical parameters directly influencing attenuation coefficient and it has been observed that with increasing plastic strain accumulation, ultrasonic attenuation increases. Between two primary echoes of ultrasonic spectra, some secondary defect echoes have been found. A damage descriptor has been introduced by taking difference between the bandwidth of defect echo and backwall echo normalized by overall amplitude frequency distributions of backwall echo. It has been found to bear sensitivity towards surface crack density. This quantitative estimation differentiates between the classical descriptions of damage due to dislocation mediated plasticity, micro crack generation and coalescence