“Cavity” formation in superplastically deformed aluminium alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 958-959
Author(s):  
A. Cziráki ◽  
E. Ková-csetényi ◽  
T. Torma ◽  
T. Turmezey
Keyword(s):  
Grain Boundaries ◽  
Aluminium Alloys ◽  
Superplastic Deformation ◽  
Volume Fraction ◽  
Superplastic Forming ◽  
Polished Surface ◽  
Cavity Formation ◽  
Stress Concentrations ◽  
Electron Microscopic ◽  
Commercial Aluminium

It is known that the formation of cavities during superplastic deformation can be correlated with the development of stress concentrations at irregularities along grain boundaries such as particles, ledges and triple points. In commercial aluminium alloys Al-Fe-Si particles or other coarse constituents may play an important role in cavity formation.Cavity formation during superplastic deformation was studied by optical metallography and transmission scanning electron microscopic investigations on Al-Mg-Si and Al-Mg-Mn alloys. The structure of particles was characterized by selected area diffraction and X-ray micro analysis. The volume fraction of “voids” was determined on mechanically polished surface.It was found by electron microscopy that strongly deformed regions are formed during superplastic forming at grain boundaries and around coarse particles.According to electron diffraction measurements these areas consist of small micro crystallized regions. See Fig.l.Comparing the volume fraction and morphology of cavities found by optical microscopy a good correlation was established between that of micro crystalline regions.

Mechanical Properties of 5083 SPF After Superplastic Deformation

1990 ◽  
Vol 196 ◽  
Author(s):  
Barry J Dunwoody ◽  
R J Stracey ◽  
A J Barnes
Keyword(s):  
Mechanical Properties ◽  
Aluminium Alloys ◽  
Superplastic Deformation ◽  
Superplastic Forming ◽  
Mechanical Processing ◽  
Fine Grain ◽  
Forming Characteristics ◽  
Second Category

ABSTRACTSuperplastic aluminium alloys may be divided into two categories: those which recrystallise dynamically during superplastic deformation, such as the Supral alloys (2004 SPF) and 8090 SPF and, secondly those in which the fine grain necessary for superplasticity is produced by static recrystallisation during thermo-mechanical processing.Both 7475 SPF and 5083 SPF belong to the second category.This paper describes the superplastic forming characteristics of 5083 SPF and its post-formed mechanical properties.Some typical applications will be shown to demonstrate the degree of complexity which is possible with this non-heat treatable alloy.

Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 176-177
Author(s):  
D. E. Fornwalt ◽  
A. R. Geary ◽  
B. H. Kear
Keyword(s):  
Electron Microscope ◽  
Grain Boundaries ◽  
Volume Fraction ◽  
Rupture Life ◽  
Stress Rupture ◽  
High Volume ◽  
Precipitate Morphology ◽  
Stress Rupture Life ◽  
Nickel Base ◽  
Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

scholarly journals Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

2021 ◽  
Author(s):  
A. Bauer ◽  
M. Vollmer ◽  
T. Niendorf
Keyword(s):  
Martensitic Transformation ◽  
Grain Boundary ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Grain Boundaries ◽  
Tensile Tests ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Grain Orientations ◽  
High Degree

AbstractIn situ tensile tests employing digital image correlation were conducted to study the martensitic transformation of oligocrystalline Fe–Mn–Al–Ni shape memory alloys in depth. The influence of different grain orientations, i.e., near-〈001〉 and near-〈101〉, as well as the influence of different grain boundary misorientations are in focus of the present work. The results reveal that the reversibility of the martensite strongly depends on the type of martensitic evolving, i.e., twinned or detwinned. Furthermore, it is shown that grain boundaries lead to stress concentrations and, thus, to formation of unfavored martensite variants. Moreover, some martensite plates seem to penetrate the grain boundaries resulting in a high degree of irreversibility in this area. However, after a stable microstructural configuration is established in direct vicinity of the grain boundary, the transformation begins inside the neighboring grains eventually leading to a sequential transformation of all grains involved.

Study on Cavity Growth in Uniaxial Tension of ZK60 Magnesium Alloy

2007 ◽  
Vol 353-358 ◽  
pp. 687-690
Author(s):  
Yan Dong Yu ◽  
De Liang Yin ◽  
Bao You Zhang
Keyword(s):  
Volume Fraction ◽  
Cavity Growth ◽  
Experimental Studies ◽  
Superplastic Forming ◽  
Cavity Radius ◽  
Analysis Software ◽  
Mixed Characteristic ◽  
Substantial Growth ◽  
Zk60 Magnesium Alloy ◽  
Electronic Microscope

Cavity growth is a typical microstructure feature in superplastic forming (SPF) of materials. Substantial growth and interlink of cavities in superplastic deformation usually lead to reduction in elongation, even to failure. Consequently, it is necessary to investigate the mechanism and model of cavity growth. In this paper, experimental studies on cavity growth were carried out by means of superplastic tension of ZK60 magnesium alloys. Scanning electronic microscope (SEM) was employed for observation of fractography. Experimental cavity radius and volume fraction were determined by optical microscopy and corresponding picture-based analysis software. It is found that, the fractured surfaces after a superplastic elongation have a mixed characteristic of intergranular cavities and dimples. Further, the cavity growth is identified to follow a exponentially increasing mode.

Formabilities of C-Si-Al-Mn Transformation-Induced Plasticity-Aided Martensitic Sheet Steel

2016 ◽  
Vol 838-839 ◽  
pp. 546-551
Author(s):  
Junya Kobayashi ◽  
Yumenori Nakashima ◽  
Koh Ichi Sugimoto ◽  
Goroh Itoh
Keyword(s):  
Tensile Strength ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Lath Martensite ◽  
Sheet Steel ◽  
Void Formation ◽  
High Volume ◽  
Stress Concentrations ◽  
Transformation Induced Plasticity ◽  
Al Content

The substitution of Si with Al in 0.2%C-1.5%Si-1.25%Mn-0.2%Cr ultrahigh strength transformation-induced plasticity (TRIP)-aided martensitic (TM) sheet steel improves galvanization. The effect of Al content on the microstructure and formabilities of the TM steel was therefore investigated. Replacement of Si with Al maintained the high volume fraction of the retained austenite and the high stretch-formability and stretch-flangeability, whereas it decreased the tensile strength. Complex addition of Si and Al yielded the best formabilities with 1.5 GPa tensile strength grade. The superior formabilities of Si-Al bearing TM steel were attributed to the strain-induced transformation of the metastable retained austenite and the relatively soft lath-martensite structure matrix. The former leads to plastic relaxation of the localized stress concentrations, thus suppressing void formation.

scholarly journals Effect of Zr Addition on the Mechanical Properties and Superplasticity of a Forged SP700 Titanium Alloy

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 906
Author(s):  
Dong Han ◽  
Yongqing Zhao ◽  
Weidong Zeng
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Titanium Alloy ◽  
Tensile Properties ◽  
Superplastic Deformation ◽  
Volume Fraction ◽  
Tensile Elongation ◽  
Β Phase ◽  
Zr Addition ◽  
Fine Microstructure

The present study focuses on the effect of 1% Zr addition on the microstructure, tensile properties and superplasticity of a forged SP700 alloy. The results demonstrated that Zr has a significant effect on inhibiting the microstructural segregation and increasing the volume fraction of β-phase in the forged SP700 alloy. After annealing at 820 °C for 1 h and aging at 500 °C for 6 h, the SP700 alloy with 1% Zr showed a completely globular and fine microstructure. The yield strength, ultimate tensile strength and tensile elongation of the alloy with optimized microstructure were 1185 MPa, 1296 MPa and 10%, respectively. The superplastic deformation was performed at 750 °C with an elongation of 1248%. The improvement of tensile properties and superplasticity of the forged SP700 alloy by Zr addition was mainly attributed to the uniform and fine globular microstructures.

Experimental Study of Grinding Characteristics on SiCp/Al Composites

2011 ◽  
Vol 487 ◽  
pp. 135-139 ◽  
Author(s):  
Li Zhou ◽  
Shu Tao Huang ◽  
Xiao Lin Yu
Keyword(s):  
Volume Fraction ◽  
Ground Surface ◽  
Diamond Wheel ◽  
Feed Speed ◽  
Grinding Forces ◽  
Electron Microscopic ◽  
Sic Particles ◽  
Scanning Electron Microscopic ◽  
Grinding Machine ◽  
Sic Particle

This paper deals with the grinding performances of SiCp/Al composites with higher volume fraction and larger SiC particle. The effects of the grinding parameters on the grinding force, removal mechanisms of SiC particles have been investigated. The grinding tests were carried out by using diamond wheel on surface grinding machine. The results indicate that the feed speed of worktable has more significant effect on the grinding forces than that of grinding depth. The scanning electron microscopic images of the machined surfaces indicate that the material removal of SiC particles was primarily due to the failure of the interface between the reinforcement and matrix, and resulting from microcracks along the interface and many fracture or crushed SiC particles on the ground surface.

scholarly journals A Tool for Local Thickness Determination and Grain Boundary Characterization by CTEM and HRTEM Techniques

2015 ◽  
Vol 21 (2) ◽  
pp. 422-435 ◽  
Author(s):  
Ákos K. Kiss ◽  
Edgar F. Rauch ◽  
Béla Pécz ◽  
János Szívós ◽  
János L. Lábár
Keyword(s):  
Grain Boundaries ◽  
Software Tool ◽  
Hexagonal Crystal ◽  
Electron Microscopic ◽  
Orientation Data ◽  
New Approach ◽  
Polycrystalline Thin Films ◽  
Transmission Electron ◽  
Transmission Electron Microscopic

AbstractA new approach for measurement of local thickness and characterization of grain boundaries is presented. The method is embodied in a software tool that helps to find and set sample orientations useful for high-resolution transmission electron microscopic (HRTEM) examination of grain boundaries in polycrystalline thin films. The novelty is thesimultaneoustreatment of the two neighboring grains and orienting both grains and the boundary planesimultaneously. The same metric matrix-based formalism is used for all crystal systems. Input into the software tool includes orientation data for the grains in question, which is determined automatically for a large number of grains by the commercial ASTAR program. Grain boundaries suitable for HRTEM examination are automatically identified by our software tool. Individual boundaries are selected manually for detailed HRTEM examination from the automatically identified set. Goniometer settings needed to observe the selected boundary in HRTEM are advised by the software. Operation is demonstrated on examples from cubic and hexagonal crystal systems.

Atomie and Electron Structure of Diamond Grain boundaries in a Polycrystalline Film

1997 ◽  
Vol 472 ◽  
Author(s):  
Hideki Ichinose ◽  
Megumi Nakanose ◽  
Yaogan Zhang
Keyword(s):  
Grain Boundaries ◽  
Polycrystalline Diamond ◽  
High Resolution Electron Microscopy ◽  
Electron Structure ◽  
Polished Surface ◽  
Resolution Electron ◽  
Diamond Grain ◽  
Electron Energy Loss ◽  
Π State ◽  
Polycrystalline Diamond Film

AbstractA polycrystalline diamond film was grown on the polished surface of silicon substrate in H2-CO-O2 mixing gas. Atomic and electron structure of grain boundaries in the film was investigated by both high resolution electron microscopy and electron energy loss spectroscopy. CSL boundaries in the film showed characteristic feature in atomic structure; Σ 9 CSL boundary was parallel not to (221) plane but to (114) plane. A new line which correspond to π * state was found in addition to major σ * line in the EELS spectra of the boundary which contained three coordinate atoms. Observed π * line shows occurred change of a dangling bond (pz electron) to π state. No π * line appeared in the EELS spectra obtained from boundaries which contained no three coordinate atom such as (111) Σ 3 boundary.

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