Improvement of Mechanical Properties by Two-Step Aging in Ultrafine Grained Al-Ag-Sc Alloy

2014 ◽  
Vol 794-796 ◽  
pp. 857-863
Author(s):  
Daisuke Terada ◽  
Yan Zeng ◽  
Nobuhiro Tsuji
Keyword(s):  
Mechanical Properties ◽  
Grain Boundaries ◽  
Tensile Elongation ◽  
The Other ◽  
Al Alloy ◽  
Other Hand ◽  
Heat Treated ◽  
Ultrafine Grained ◽  
The Matrix ◽  
The Difference

In order to improve limited ductility of ultrafine grained (UFG) Al alloys, mechanical properties of an UFG Al alloy having fine precipitates within grains were investigated. An Al-0.2wt%Sc-4.2wt%Ag alloy was severely deformed by the ARB process at room temperature and subsequently heat-treated by a two-step aging. After the first aging in the two-step aging, fine Al3Sc precipitates were formed. In the specimen ARB processed by 4cycles, the fine Al3Sc precipitates were homogeneously dispersed within the grains. On the other hand, in the specimen ARB processed by 8 cycles, Al3Sc precipitates were linearly-aligned on the grain boundaries that had moved during the heat treatment. After the second aging, fine G.P. zones of Ag as well as Ag2Al precipitates were observed within the grains in the specimen ARB processed by 4 cycles. Coarse precipitates of Ag2Al at grain boundaries were observed in the specimen ARB processed by 8 cycles. The difference in the distribution of precipitates was considered to be due to the difference in fraction of high angle grain boundaries in the matrix microstructures. The strength of the solution treated specimen increased by the two-step aging while the tensile elongation decreased. On the other hand, both of the strength and elongation of the specimen ARB processed by 4 cycles increased after the two-step aging. In case of the specimen ARB processed by 8 cycles, the strength decreased slightly and the elongation increased by the two-step aging, and the aged specimen exhibited a good balance between strength and elongation.

The effect of ageing duration on the mechanical properties of Al alloy 6061-garnet composites

2001 ◽  
Vol 215 (2) ◽  
pp. 113-119
Author(s):  
S C Sharma
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Al Alloy ◽  
Destructive Testing ◽  
Transmission Electron ◽  
Heat Treated ◽  
The Matrix ◽  
Reinforcing Particle ◽  
Alloy 6061

A well-consolidated composite of Al alloy 6061 reinforced with 4, 8 and 12 wt% garnet was prepared by a liquid metallurgy technique, the composite was heat treated for different ageing durations (T6 treatment), and its mechanical properties were determined by destructive testing. The results of the study indicated that, as the garnet particle content in the composites increased, there were marked increases in the ultimate tensile strength, compressive strength and hardness but there was a decrease in the ductility. There was an improvement in the tensile strength, compressive strength, and hardness with ageing due to precipitation. Precipitation in Al alloy 6061, with and without garnet particulate reinforcement, was studied using transmission electron microscopy. The fracture behaviour of the composites was altered significantly by the presence of garnet particles and the crack propagation through the matrix, and the reinforcing particle clusters resulted in final fracture.

Microstructure and Mechanical Properties of Al-0.5 at.% X (=Si, Ag, Mg) Alloys Highly Deformed by ARB Process

2008 ◽  
Vol 584-586 ◽  
pp. 547-552 ◽  
Author(s):  
Daisuke Terada ◽  
Toshiaki Masui ◽  
Naoya Kamikawa ◽  
Nobuhiro Tsuji
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Microstructure Evolution ◽  
High Purity ◽  
Uniform Elongation ◽  
Mg Alloys ◽  
The Other ◽  
Other Hand ◽  
The Difference ◽  
Lamellar Boundary

Effect of solid solution elements on microstructure evolution and mechanical properties was investigated using a high purity Al (purity 99.99%) and Al-0.5 at.% X ( X = Si, Ag, Mg ) alloys deformed by accumulative roll bonding (ARB) process up to 7 cycles (equivalent strain of 5.6) at ambient temperature. The ARB-processed high purity Al showed the equiaxed microstructure having mean grain size of 750 nm. On the other hand, the microstructure of the ARB-processed Al-0.5at.%X alloys showed lamellar boundary structures elongated along RD. The mean lamellar boundary spacing significantly differed depending on the alloying elements, which suggested that solute atoms had a significant effect on microstructure evolution. The difference in the grain size was regarded to be caused by the difference in recovery processes in the alloys. The tensile strength of the alloys increased with increasing the number of ARB cycles. In the Al-Si and Al-Ag alloys, the post-uniform elongation increased with increasing the number of the ARB cycles. On the other hand, the elongation of the Al-Mg hardly changed during the ARB process.

scholarly journals Propagation of Selected Pear and Quince Rootstocks By Hardwood Cuttings

2016 ◽  
Vol 64 (4) ◽  
pp. 1211-1217 ◽  
Author(s):  
Tomáš Nečas ◽  
Luděk Laňar ◽  
Ivo Ondrášek ◽  
Jan Náměstek ◽  
Jakub Láčík ◽  
...  
Keyword(s):  
Ethanol Solution ◽  
The Other ◽  
Naphthalene Acetic Acid ◽  
Rooted Cuttings ◽  
Beneficial Effects ◽  
Heat Stimulation ◽  
Other Hand ◽  
Heat Treated ◽  
The Difference ◽  
Made In

As long as new rootstocks continue to be developed, there will always the need for new genotypes to be controlled and evaluated. This study involves verification of selected rootstocks with reference to growth, propagation ability and other characteristics. Different rootstocks, different growth stimulators and different kinds of cuttings techniques were adopted for these experiments. Stimulators used for evaluations included: 1 % Racine (2.5 % naphthalene acetic acid - NAA), 0.5 % Rhizopon AA (2.5 % indole-3-butyric acid - IBA) and 0.25 % IBA in 50 % ethanol solution. There were three sets of experiments in all. In Experiment 1, the bases of cuttings were treated with the stimulators and part of them was also treated with heat before planting. Results from Experiment 1 indicated that cuttings treated with Rhizopon AA produced the best effect after heat treatment (with an overall average of 36.9 % of rooted cuttings). Pyrodwarf (78.7 %), Cydomalus (73.9 %) and Pyroplus (60.6 %) were the best performing rootstocks among the evaluated ones. In Experiment 2, we evaluated the influence of the date of harvesting the cuttings on rooting (comparisons were made between cuttings prepared in December [early] and March [late]). For BA29 rootstock cuttings, the best performance was attained by cuttings taken in March. The difference in rooting between March and December was 43.9 %. On the other hand, early harvested rootstocks (cuttings taken in December) for Cydomalus showed the best performance, with an 18.7 % difference between cuttings made in December and in March. Results from other evaluated rootstocks were not significant enough. In Experiment 3, the effect of chemical (phytohormone) stimulation and heat stimulations was compared. The best result was obtained by combinations of treatments without heat stimulations, when the cuttings were stored at 5°C and later treated with 0.25 % IBA in 50 % ethanol solution. The least rooting results, on the other hand, were observed in heat treated cuttings, in cuttings stimulated with IBA and subsequently with heat and in cuttings treated with a 3 cm radial cut at the base. Based on our findings we cannot prove clearly that heat stimulation and the phytohormones used have beneficial effects on rooting of especially new rootstock genotypes with an unknown propagation coefficient. This means that propagation using cuttings still remains an interesting topic to be further researched.

Defects in Aluminum Alloy Castings

2019 ◽  
Author(s):  
John Campbell
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Hydrogen Embrittlement ◽  
Stress Corrosion Cracking ◽  
Tensile Elongation ◽  
Shrinkage Porosity ◽  
Corrosion Cracking ◽  
The Other ◽  
Al Alloy ◽  
Alloy Castings

Most of the major defects in Al alloy castings are the result of entrainment processes. The entrainment of the surface of the liquid creates bifilm defects, and the entrainment of air creates bubbles and bubble trails. Occasionally the entrainment of foreign inclusions, such as sand inclusions, can also be a problem. Bifilms form the initiators of gas porosity, shrinkage porosity, hot tears, and cracks. Since bifilms can be controlled by improved melting and casting techniques, all these defects are controllable. In addition, bifilms control the mechanical properties of castings, particularly tensile elongation, toughness, and fatigue. The other important effects caused by bifilms such as invasive corrosion behavior including pitting, stress corrosion cracking, and possibly hydrogen embrittlement, are beyond the scope of this review.

scholarly journals Improvements in Aggregate-Paste Interface by the Hydration of Steelmaking Waste in Concretes and Mortars

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1147 ◽  
Author(s):  
Isabel Miñano ◽  
Francisco Benito ◽  
Manuel Valcuende ◽  
Carlos Rodríguez ◽  
Carlos Parra
Keyword(s):  
Mechanical Properties ◽  
Chemical Interaction ◽  
Raw Materials ◽  
The Other ◽  
Reaction Products ◽  
Hydrated Calcium Silicate ◽  
Limestone Aggregate ◽  
Other Hand ◽  
The Matrix ◽  
New Compounds

The objective of the experimental work is to study the mechanical properties in self-compacting concretes (SCC) in which part of the limestone aggregate has been replaced by granulated blast furnace slag (GBFS) in different percentages ranging from 0% to 60%. The results show that at early ages the SCC with the largest content in slag tend to have lower compressive strengths due to the poor compacting of the aggregates, although in the long-term their strength increases due to the reactivity of the slag. In fact, at the age of 365 days, the mortars made with the substitution of 50% of cement by ground GBFS reach compressive strength similar to that of the mortar made with 100% of cement. The consumption of calcium hydroxide during the hydration of the GBFS and the formation of hydrated calcium silicate (CSH) improve the mechanical properties of the slag-paste interface. The new compounds formed by the hydration of anhydrous oxides of the GBFS improve the aggregate-paste transition zone. The chemical interaction between the dissolution of the cement pore and the GBFS ends up generating new compounds on its surface. The increasing hydration of the GBFS produces a greater amount of silica gel that polymerises, densifying the matrix and reducing the porosity, which improves the mechanical properties of the concrete and perhaps its durability. The topography of the particles and their interface are analysed with atomic force microscopy techniques to assess the morphology depending on the aggregate used. On the other hand, a study was carried out of the aggregate-paste interface with scanning electronic microscope at different ages. It can be seen that in the contours of the hydrated GBFS particles, a band or ring forms with the new reaction products. The results obtained strengthen the previous conclusions. The new hydrated compounds fill the reaction ring, introducing chemical bonds between the aggregate and the interface, occupying part of the original pores or substituting spaces occupied originally by large portlandite crystals, of lesser mechanical strength and easily leached. For all this, the benefit is twofold. On the one hand, use is made of industrial by-products and, on the other hand, part of the destruction of natural quarries to obtain the necessary raw materials is avoided.

Interfaces in a slowly cooled Al-SiC composite

1990 ◽  
Vol 48 (4) ◽  
pp. 380-381
Author(s):  
Asgeir Bardal ◽  
Ragnvald Høier
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Dislocation Density ◽  
Physical Properties ◽  
Local Structure ◽  
Room Temperature ◽  
Al Alloy ◽  
Unreinforced Alloy ◽  
Heat Treated ◽  
The Matrix

In various metal-based composites ceramical powders are added for increased mechanical properties. Commercial materials are made through different production routes and in all cases the physical properties are determined by the production determined microstructure, i.e. by the grain and particle size, the dislocation density and the local structure near and at the interface between the matrix and the ceramical powder. In the present studies it has been focused on the two latter aspects.The matrix of the material investigated is the commercial Al alloy AA6061, with Mg and Si as the major alloying elements, and the powder added is SiC. The material has been subject to various heat-treatments and is being studied by use of TEM, EELS and EDS. In this work we will focus on material produced via a powder route, and specimens which have been heat treated at 400°C for 8 hours, extruded, slowly cooled (l°C/min) down to 180°C and then quenched to room temperature. This gives a material with good ductility, strength a little lower than the unreinforced alloy and a stiffness which is about 50% higher.

Mechanical Properties and Aging Behavior of Ultrafine Grained Al-Ag Alloy Fabricated by Accumulative Roll-Bonding

2014 ◽  
Vol 794-796 ◽  
pp. 851-856
Author(s):  
Tadashiege Nagae ◽  
Nobuhiro Tsuji ◽  
Daisuke Terada
Keyword(s):  
Mechanical Properties ◽  
Grain Refinement ◽  
Accumulative Roll Bonding ◽  
Precipitation Hardening ◽  
Tensile Elongation ◽  
Solution Treatment ◽  
High Strength ◽  
Subsequent Aging ◽  
Roll Bonding ◽  
Ultrafine Grained

Accumulative roll-bonding (ARB) process is one of the severe plastic deformation processes for fabricating ultrafine grained materials that exhibit high strength. In aluminum alloys, aging heat treatment has been an important process for hardening materials. In order to achieve good mechanical properties through the combination of grain refinement hardening and precipitation hardening, an Al-4.2wt%Ag binary alloy was used in the present study. After a solution treatment at 550°C for 1.5hr, the alloy was severely deformed by the ARB process at room temperature (RT) up to 6 cycles (equivalent strain of 4.8). The specimens ARB-processed by various cycles (various strains) were subsequently aged at 100, 150, 200, 250°C, and RT. The hardness of the solution treated (ST) specimen increased by aging. On the other hand, hardness of the ARB processed specimen decreased after aging at high temperatures such as 250°C. This was probably due to coarsening of precipitates or/and matrix grains. The specimen aged at lower temperature showed higher hardness. The maximum harnesses achieved by aging for the ST specimen, the specimens ARB processed by 2 cycles, 4 cycles and 6 cycles were 55HV, 71HV, 69HV and 65HV, respectively. By tensile tests it was shown that the strength increased by the ARB process though the elongation decreased significantly. However, it was found that the tensile elongation of the ARB processed specimens was improved by aging without sacrificing the strength. The results suggest that the Al-Ag alloy having large elongation as well as high strength can be realized by the combination of the ARB process for grain refinement and the subsequent aging for precipitation hardening.

scholarly journals Preparation of Long Sisal Fiber-Reinforced Polylactic Acid Biocomposites with Highly Improved Mechanical Performance

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1124
Author(s):  
Zhifang Liang ◽  
Hongwu Wu ◽  
Ruipu Liu ◽  
Caiquan Wu
Keyword(s):  
Mechanical Properties ◽  
Polylactic Acid ◽  
Mechanical Performance ◽  
Tensile Elongation ◽  
Sisal Fiber ◽  
Fiber Reinforced ◽  
Impact Performance ◽  
The Matrix ◽  
Blending Process ◽  
Extension Direction

Green biodegradable plastics have come into focus as an alternative to restricted plastic products. In this paper, continuous long sisal fiber (SF)/polylactic acid (PLA) premixes were prepared by an extrusion-rolling blending process, and then unidirectional continuous long sisal fiber-reinforced PLA composites (LSFCs) were prepared by compression molding to explore the effect of long fiber on the mechanical properties of sisal fiber-reinforced composites. As a comparison, random short sisal fiber-reinforced PLA composites (SSFCs) were prepared by open milling and molding. The experimental results show that continuous long sisal fiber/PLA premixes could be successfully obtained from this pre-blending process. It was found that the presence of long sisal fibers could greatly improve the tensile strength of LSFC material along the fiber extension direction and slightly increase its tensile elongation. Continuous long fibers in LSFCs could greatly participate in supporting the load applied to the composite material. However, when comparing the mechanical properties of the two composite materials, the poor compatibility between the fiber and the matrix made fiber’s reinforcement effect not well reflected in SSFCs. Similarly, the flexural performance and impact performance of LSFCs had been improved considerably versus SSFCs.

scholarly journals Another Name for Liberty: Revelation, ‘Objectivity,’ and Intellectual Freedom in Barth and Marion

Open Theology ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 430-450
Author(s):  
Kristóf Oltvai
Keyword(s):  
A Priori ◽  
The Other ◽  
Christian Theology ◽  
Intellectual Freedom ◽  
Specific Kind ◽  
Absolute Truth ◽  
Saturated Phenomenon ◽  
Other Hand ◽  
The Difference ◽  
The Relationship

Abstract Karl Barth’s and Jean-Luc Marion’s theories of revelation, though prominent and popular, are often criticized by both theologians and philosophers for effacing the human subject’s epistemic integrity. I argue here that, in fact, both Barth and Marion appeal to revelation in an attempt to respond to a tendency within philosophy to coerce thought. Philosophy, when it claims to be able to access a universal, absolute truth within history, degenerates into ideology. By making conceptually possible some ‚evental’ phenomena that always evade a priori epistemic conditions, Barth’s and Marion’s theories of revelation relativize all philosophical knowledge, rendering any ideological claim to absolute truth impossible. The difference between their two theories, then, lies in how they understand the relationship between philosophy and theology. For Barth, philosophy’s attempts to make itself absolute is a produce of sinful human vanity; its corrective is thus an authentic revealed theology, which Barth articulates in Christian, dogmatic terms. Marion, on the other hand, equipped with Heidegger’s critique of ontotheology, highlights one specific kind of philosophizing—metaphysics—as generative of ideology. To counter metaphysics, Marion draws heavily on Barth’s account of revelation but secularizes it, reinterpreting the ‚event’ as the saturated phenomenon. Revelation’s unpredictability is thus preserved within Marion’s philosophy, but is no longer restricted to the appearing of God. Both understandings of revelation achieve the same epistemological result, however. Reality can never be rendered transparent to thought; within history, all truth is provisional. A concept of revelation drawn originally from Christian theology thus, counterintuitively, is what secures philosophy’s right to challenge and critique the pre-given, a hermeneutic freedom I suggest is the meaning of sola scriptura.

Markedness and Perspective in the Interpretation of the Active and Passive Voice

1974 ◽  
Vol 26 (2) ◽  
pp. 189-195 ◽  
Author(s):  
Irene Klenbort ◽  
Moshe Anisfeld
Keyword(s):  
Information Content ◽  
Focal Point ◽  
The Other ◽  
Clear Pattern ◽  
Passive Voice ◽  
Other Hand ◽  
Logical Subject ◽  
The Difference

The subjects were presented with active and passive sentences. For each sentence, they had to choose between two alternative implications. The pattern of choices indicates that in the passive the logical subject was interpreted by the subjects as the focal point of the information asserted by the sentence and as the carrier of overall responsibility for the sentential proposition. In contrast to the passive, there was no clear pattern of preferences for the active. The difference between the two voices was attributed to their markedness asymmetry, the passive being marked and the active unmarked. It is concluded that the active offers a neutral structure for conveying information; a structure available for use when one does not want to superimpose on the information content any stylistic or connotational implications. The passive, on the other hand, suggests special connotations in addition to the basic message.

Sign in / Sign up

Export Citation Format

Share Document