Mechanical Behavior and Plastic Instabilities of Compressed Al Metals and Alloys Investigated with Intensive Strain and Acoustic Emission Methods

Pawełek, A.

doi:10.5772/19694

Cited by 3 publications

(12 citation statements)

References 25 publications

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“…This is a well known fact in literature (see e.g. [8]), and we discuss the AE behaviour after this maximum. Similarly, the high AE peak appearing often at the end of test is related to the breaking of the sample.…”

Section: Mg4li5al Alloys -Tensile Testsmentioning

confidence: 94%

“…It is strongly suggested in papers [6,8,10,11], that also the contribution to AE signals may originate from the synchronized of both, internal and surface annihilation of many dislocations. Fig.7 and 8 present corresponding TEM pictures observed after tensile tests of Mg4Li5Al alloy at 150ºC and 200ºC, respectively.…”

Section: Mg4li5al Alloys -Tensile Testsmentioning

confidence: 99%

“…Series of alloys used in this study were prepared by casting of raw materials in a steel crucible at 800°C with subsequent pouring into a cooled steel mould in a chamber of vacuum induction furnace (Balzers) under low argon pressure (1000 Pa, of 99.999% purity) after previous evacuation (10 -2 Pa). The applied preparation procedure was similar to that reported in [15] and used also in our previous works [5][6][7][8][9]. Then, the alloys were machined into standard specimens with rectangular cross-section.…”

Section: Compression and Tensile Testsmentioning

confidence: 99%

“…It is worth to emphasize here that the relation between the AE activity (AE local peaks) and the PL effect (which accompanies local jumps of external stresses), according to [8,11], may be quite well explained in terms of collective and accelerated movement of many dislocations generated in single slip planes by the sources which are alternately active and blocked by solute atoms (Cottrell atmospheres). It is strongly suggested in papers [6,8,10,11], that also the contribution to AE signals may originate from the synchronized of both, internal and surface annihilation of many dislocations.…”

Section: Mg4li5al Alloys -Tensile Testsmentioning

confidence: 99%

“…The occurrence of hot-shortness phenomenon, followed by the fracture of intercrystalline character is an important reason for technological difficulties. Previous investigations of the authors of the paper [5][6][7][8][9] of mechanical properties of alloys with the application of AE method were devoted to the Mg-Li-Al alloys and related composites generally in the context of the method of intensive deformation processes leading to their excellent mechanical properties, such as great strength and plasticity or even superplasticity. On the other hand, the investigations of metal and alloy plastic instability using the AE technique were carried out [10][11][12] mainly in the context of basic aspects of PL effect, twinning or shear band in both poly-and single metal and alloy crystals.…”

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confidence: 99%

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Plastic Instabilities Induced by the Portevin - Le Châtelier Effect and Fracture Character of Deformed Mg-Li Alloys Investigated Using the Acoustic Emission Method

Pawełek

Piątkowski

Wajda

et al. 2016

Archives of Metallurgy and Materials

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IntroductionUnsatisfying ability to plastic deformation at elevated temperatures, mostly leading to the reduction of deformability and/or hot plasticity is characteristic for many metals and alloys [1][2][3][4]. The occurrence of hot-shortness phenomenon, followed by the fracture of intercrystalline character is an important reason for technological difficulties. Previous investigations of the authors of the paper [5][6][7][8][9] of mechanical properties of alloys with the application of AE method were devoted to the Mg-Li-Al alloys and related composites generally in the context of the method of intensive deformation processes leading to their excellent mechanical properties, such as great strength and plasticity or even superplasticity. On the other hand, the investigations of metal and alloy plastic instability using the AE technique were carried out [10][11][12] mainly in the context of basic aspects of PL effect, twinning or shear band in both poly-and single metal and alloy crystals. The fracture and strengthening properties of Mg-Li based alloys (and composites) were investigated, for example in [13][14][15][16], but without the use of AE method, which proved to be a very useful technique of material examination. In this work the results of the investigations of the correlation between the AE phenomenon, the plastic instability, induced by PL effect, twining or shear bands, and the both, intergranular and transcrystalline fracture of Mg4Li5Al and Mg4Li4Zn alloys subjected to tensile and compression tests at wide range of elevated temperatures are presented.Alloys based on magnesium with lithium, as the lightest ones from among the known metallic construction materials, are very attractive from the point of view of their application as the materials for light, yet durable constructions to be used in the automotive industry (e.g. car engine housings), light housings of computers and aerospace technology. The basic Mg-Li alloys exist in three phase areas. The hexagonal α phase appears in the concentration range of Li up to 4 wt.%. If the content of Li is more than 12 wt.% -the β phase of cubic lattice occurs. The alloys of Li content from 4% up to 12 wt.% form the α+β two-phase mixture. The mechanical properties of α phase are worse from that of the β phase, which is more plastic and thus reveals good machinability and weldability. Alloying additions, e.g. Al (or Zn) from 3% to 5%, slightly increase the density of the alloy, but lead to the precipitation of coherent particles of transition phase, θ-MgLi 2 Al/θ-MgLi 2 Zn, which additionally strengthens the matrix and leads to the improvement of mechanical properties [14]. The present paper addresses the optical microscopic, as well as TEM and SEM observations of the failure of samples after tensile and compression tests.

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Section: Mg4li5al Alloys -Tensile Testsmentioning

confidence: 94%

Section: Mg4li5al Alloys -Tensile Testsmentioning

confidence: 99%

Section: Compression and Tensile Testsmentioning

confidence: 99%

Section: Mg4li5al Alloys -Tensile Testsmentioning

confidence: 99%

mentioning

confidence: 99%

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Plastic Instabilities Induced by the Portevin - Le Châtelier Effect and Fracture Character of Deformed Mg-Li Alloys Investigated Using the Acoustic Emission Method

Pawełek

Piątkowski

Wajda

et al. 2016

Archives of Metallurgy and Materials

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Mechanisms of plastic instability and fracture of compressed and tensile tested Mg-Li alloys investigated using the acoustic emission method

Pawełek¹,

Piątkowski²,

Wajda³

et al. 2015

Frattura Ed Integrità Strutturale

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The results of the investigation of both mechanical and acoustic emission (AE) behaviors of Mg4Li5Al alloy subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloy and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the possible influence of factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries or solute atoms along dislocations (Cottrell atmospheres) or dislocation pile-ups at grain boundaries which create very high stress concentration leading to fracture. The results show that the plastic instabilities are related to the Portevin-Le Châtelier phenomenon (PL effect) and they are correlated with the generation of AE peaks. The fractography of breaking samples was analyzed on the basis of light (optical), TEM and SEM images.

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Behaviour of Acoustic Emission in Deformation and Microcracking Processes of Mg Alloys Matrix Composites Subjected to Compression Tests

Pawełek¹,

Ozgowicz²,

Ranachowski³

et al. 2017

ACRI

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This work was carried out in collaboration between all authors. Author AP designed the study, interpreted the mechanical and AE results and wrote the first draft of the manuscript. Author ZR described basic procedures of AE methods, executed measurements and performed the statistical analysis of the AE results. Author AP executed measurements of mechanical parameters in compression tests. Author PR managed the investigations of ceramic materials and processed results of compression tests. Authors SK and SKJ prepared and fabricated of the Mg Alloys Matrix Composites. Author WO managed the literaturę searches, cooperated in discussion and the analysis of the results of mechanical and acoustic measurements. All authors read and approved the final manuscript.

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Mechanical Behavior and Plastic Instabilities of Compressed Al Metals and Alloys Investigated with Intensive Strain and Acoustic Emission Methods

Cited by 3 publications

References 25 publications

Plastic Instabilities Induced by the Portevin - Le Châtelier Effect and Fracture Character of Deformed Mg-Li Alloys Investigated Using the Acoustic Emission Method

Plastic Instabilities Induced by the Portevin - Le Châtelier Effect and Fracture Character of Deformed Mg-Li Alloys Investigated Using the Acoustic Emission Method

Mechanisms of plastic instability and fracture of compressed and tensile tested Mg-Li alloys investigated using the acoustic emission method

Behaviour of Acoustic Emission in Deformation and Microcracking Processes of Mg Alloys Matrix Composites Subjected to Compression Tests

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