Dynamic Crushing Response of Closed-cell Aluminium Foams during Shock Loading

Understanding the impact response of aluminium foams is essential for assessing their energy absorption capacity under dynamic loading. In this paper, the dynamic compaction behavior of closed-cell aluminium foam (CYMAT ™) has been tested using the plate-impact technique. Post-impacted samples have been examined using optical microscopy to observe the microstructural changes with the objective of elucidating the pore-collapse mechanism.The authors also gratefully acknowledge UNSW Canberra’s Defence Related Research program that part-funded this work

A microstructural study of warm rolled interstitial free steel

published_or_final_versionMechanical EngineeringDoctoralDoctor of Philosoph

An ebsd study of nickel sheets after unidirectional and cross rolling arb processings

Copyright © 2015 MS&T15®.Commercially pure nickel sheets were processed by accumulative roll bonding (ARB) up to six cycles at room temperature in two different routes. In route one ARB was carried out conventionally and it is called U (unidirectional)-ARB. In route two the sample is rotated by 90° around the normal direction (ND) in alternating ARB cycles and it is called C (cross-rolled)-ARB. Both routes produce typical fine lath structures of severe rolling deformations. EBSD study shows that U-ARB produces typical FCC rolling textures containing Copper {112} <111>, S {123} <634> and Brass {110} <112> orientations. In comparison, C-ARB produces diffused orientation distributions with principal components distributing between Brass and {011} <111> orientations. Schmid factor calculation of the sheet around the RD shows less variation in C-ARB sample than the U-ARB sample. This implies that reduced in-plane anisotropics can be achieved by cross rolling in ARB processing

The effect of cross-rolling on the growth of goss grains in a grain oriented silicon steel

© 2016, Springer International Publishing AG. All rights reserved. A series of cross-rolled cold rolling experiments, followed by annealing experiments, were carried out on a commercial two-pass cold rolled Fe-Si alloy. Even though no major influence was observed on the primary recrystallized grains after the sheet was subjected to ~10% deformation, its effect on the texture distribution of the sheet (prior to annealing) is noticeable. The texture of the rolled sample showed increases in the {112}<111> orientation and Goss texture within a 5° spread. However, after annealing for 10 and 60 min. at 900°C, abnormal growth of Goss grains does not occur and the Goss texture gradually disappears

Time and temperature regime of continuous grain coarsening in an ECAP-processed Al(0.1 wt.% Sc) alloy

An equiaxed, submicron grain size distribution was generated in an Al(0.1 wt.% Sc) alloy by processing through equal channel angular pressing followed by a low temperature pre-ageing heat treatment. The alloy was subsequently annealed for various times at 300, 350, 400 and 450 °C for investigating the thermal stability of the deformation microstructure. It was found that up to 400 °C, the submicron grain structure coarsens slowly and uniformly by a process of continuous recrystallization. Within this temperature range, the uniform dispersion of nano-sized Al 3Sc particles generated by the pre-ageing treatment substantially hinders grain coarsening by Zener pinning of the (sub)grain boundaries. At the higher annealing temperature of 450 °C, certain grains were found to grow discontinuously thereby generating a mixed microstructure consisting of both fine and coarse grains. The data in this study was combined with recent data for a higher solute Al(0.3 wt.% Sc) alloy for furthering our understanding of the time and temperature range in which this family of alloys is resistant to rapid, discontinuous grain coarsening (recrystallization). © 2011 Elsevier Ltd. All rights reserved

The initial stages of formation of low angle boundaries within lamellar bands during accumulative roll bonding of aluminum

The nature of newly forming lamellar band boundaries was investigated in accumulative roll bonded aluminum. These boundaries initiate as low angle interfaces parallel to the existing lamellar band boundaries irrespective of the crystallographic orientation of the parent lamellar band. The transverse directions of the divided segments were found to rotate at an angle equal to the degree of misorientation between segments. Such a phenomenon is not sustained when the boundaries become high angle

Composites matching the properties of human cortical bones: The design of porous titanium-zirconia (Ti-ZrO2) nanocomposites using polymethyl methacrylate powders

Bone-like low elastic modulus micro-porous titanium (Ti) and titanium-zirconia (Ti-ZrO2) nanocomposites were fabricated by a pressureless sintering process with biocompatible polymethyl methacrylate (PMMA) powders as the pore-forming agents. A microstructural analysis revealed that the method can successfully make randomly distributed pores in the sintered monolithic and nanocomposite, and the pore-forming agents can be removed by a heat treatment process. The material properties, i.e., the relative density, pore morphology, microhardness and elastic modulus, can be dramatically altered with the pore-forming agent. Moreover, the porous Ti-based nanocomposites produced in this way (50 vol% PMMA) have interconnected pores, higher biocompatibility, better mechanical properties and well controlled the Ti grain size, when compared with the monolithic porous Ti bodies through the second phase strengthening mechanism. The elastic moduli of the highly porous monolithic Ti and Ti-ZrO2 nanocomposites can be controlled to be about 20.0 and 22.4 GPa, respectively, which are almost the same as human cortical bones (7-25 GPa)

The mode of deformation in a cold-swaged multifunctional Ti-Nb-Ta-Zr-O alloy

Multifunctional titanium alloys, termed Gum Metal™, are ß-phase Ti alloys first developed in 2003. These alloys exhibit many interesting properties including, for example, low rate of work-hardening and superplasticity during cold deformation. The original report described a new plastic deformation mechanism not involving major dislocation activity to explain such deformation behavior. In the current study, a comparable Ti-36.8Nb-2.7Zr-2.0Ta-0.44O (wt pct) alloy to the original investigators was produced by powder sintering, hot forging, solution treatment, and cold swaging with the aim at investigating the microstructural development during swaging. XRD and TEM showed that the forged/solution-treated alloy was ß-phase with a small amount of ?-phase. After cold swaging by up to 96 pct area reduction, TEM/HRTEM revealed the existence of dislocations, deformation twins, ?-phase, nanodisturbances, and lattice bending, with EBSD showing the grains to be highly elongated in the swaging direction, fragmented, and distorted. Most notably, swaging also generated a strong 〈 110âŒo fiber texture, even after moderate strains. The foregoing structural analysis provides substantial evidence that dislocations are present in the alloy after cold swaging. The major support of dislocation glide processes acting as the dominant plastic deformation mode in the swaged alloy is the strong 〈110âŒo fiber texture that develops, which is a characteristic feature of all cold-drawn/swaged body centered cubic metals and alloys. © 2013 The Minerals, Metals & Materials Society and ASM International

Engineering low intensity planar textures in commercial purity nickel sheets by cross roll bonding

© 2016 Elsevier B.V. Accumulative roll bonding is a severe plastic deformation technique capable of generating nano-scale microstructures in sheet metals. This technique can also be exploited for processing novel sheet products that are not possible through conventional rolling. In this investigation, cross rolling was combined with accumulative roll bonding of commercial purity nickel sheets, for obtaining an overall reduction in intensity of the deformation and recrystallization textures, which has been a long-time objective for obtaining drawable face centred cubic metal sheet. Overall, a significant reduction in the texture intensities were achieved by incorporating cross roll bonding. In particular, the dominance of the cube texture component, which readily forms in heavily cold rolled and annealed high stacking fault energy, face centred cubic metals and alloys, was suppressed by adopting this processing route. Texture-based Schmidt factor calculations points to a significant reduction in planar anisotropy of the cross rolled and annealed sheet, which is an important factor governing the earing propensity of deep drawn cups

Grain boundary deformation phenomena and secondary growth of goss grains in a Fe-3.5%Si steel

© 2017 ISIJ. In this investigation, a long-standing grain growth question is addressed in a Fe-3.5% Si steel. This material undergoes secondary growth of Goss oriented grains, but the underlying mechanisms of this growth remain unresolved despite extensive investigations for almost a century. In this investigation, a key question concerning this subject is resolved i.e. whether the nature of primary recrystallization grain boundaries solely determines the growth of Goss grains during secondary recrystallization. To address this issue undeformed and lightly deformed samples were subjected to recrystallization annealing under identical conditions. Although the extent of the deformation is light, such that it creates only limited modifications in the grain boundary structures, the recrystallization mechanism changes from abnormal secondary growth to conventional grain growth. In the former case, recrystallization commences at higher temperatures when the MnS inhibiting particles become dissolved, and in the latter mechanism, recrystallization occurs at lower temperatures due to the differences in stored energy between grains sharing a common boundary. This occurs through strain-induced grain boundary migration