Cast magnesium-metal matrix composites are widely used in automotive and aerospace industries due to high strength-to-weight ratio and good damping properties. In the present work, a novel hybrid method has been adopted to fabricate TiC-TiB2 reinforced magnesium matrix composites. The reinforcement is formed in-situ from elemental Ti and B4C powders and molten Mg-Al-Zn alloy without any addition of a third phase metal powder such as aluminum. Results show that the distribution of TiC and TiB2 reinforcing phases in the magnesium matrix is more uniform when the composite is fabricated at 900 °C for 2 h. The base and composite materials were subjected to homogenization treatment which resulted in dissolution of β-Mg17Al12 phase into α-Mg matrix and enhances the strength and ductility by 22% and 50% in base and 17% and 50% in composite respectively. The enhancement of mechanical properties in the homogenized in-situ composites is explained in detail by analyzing the fractographs and microstructures of the material. © 2016 Elsevier Ltd

Sushanta Kumar Panigrahi

Department of Mechanical Engineering

B. N. Sahoo

Aerospace industry

Aluminum

Characterization

Fractography

FRACTURE MECHANICS

HOMOGENIZATION METHOD

Magnesium

Magnesium alloys

Mechanical properties

Powder metals

Reinforcement

titanium

TITANIUM CARBIDE

AZ91 MAGNESIUM ALLOYS

DAMPING PROPERTY

Homogenization treatment

IN-SITU COMPOSITE

IN-SITU REACTIONS

MAGNESIUM MATRIX COMPOSITE

MG-AL -ZN ALLOYS

STRENGTH AND DUCTILITIES

Metallic matrix composites

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Materials and Design

ZE41 Mg–TiB2 metal matrix composites with improved mechanical properties were synthesized via a novel processing route. In this process, the Ti–B system was developed without addition of third intermediate metallic Al powder, thereby preventing formation of any undesirable hazardous by-products from salt system (Al–K2TiF6–KBF4) and brittle TiAl3 intermetallic phase from master alloy (Al–Ti–B). Sub-micron sized TiB2 particles (5, 10 and 15 wt%) were reinforced in the ZE41-Mg alloy and the influence of TiB2 particles and its weight fraction on mechanical properties of composite materials were studied in details with an emphasis on microstructural characterization. The microstructural characterization shows reasonable uniform distribution of TiB2 particles in lower weight fraction of reinforcement and strong interfacial bonding with the matrix. A significant enhancement of the strength as well as grain refinement of composite were observed with increased TiB2 particles. The effect of TiB2 particle content on Young's modulus and yield strength was correlated via theoretical/mathematical modeling and experimental investigations. The strengthening mechanisms for strength enhancement of composites were established. © 2019 Elsevier B.V.

Materials Science and Engineering A

Effect of in-situ sub-micron sized TiB2 reinforcement on microstructure and mechanical properties in ZE41 magnesium matrix composites

In the present work, dry sliding wear behavior of AZ91 Magnesium alloy with different microstructural conditions are investigated under a set of processing parameters. The investigations are carried out on four material conditions: (i) AZ91 Magnesium alloy, (ii) AZ91 alloy with precipitate, (iii) AZ91 alloy with in-situ TiC + TiB2 reinforcement and (iv) AZ91 alloy with both precipitate and in-situ reinforcement. The effect of microstructural modification on different wear mechanisms namely: abrasive, oxidation, delamination and melt wear is established. The processing windows for all the four types of wear mechanism are established and the wear mechanism maps are also constructed by correlating the microstructures of worn surfaces and test parameters. The inherent mechanisms of all the four types of wear behavior are established for all the material conditions. © 2019 Elsevier Ltd

Tribology International

Development of wear maps of in-situ TiC+TiB2 reinforced AZ91 Mg matrix composite with varying microstructural conditions

The present work investigated the synergetic effect of varying reinforcement sizes (12 μm (coarse), 1 μm (fine), 45 nm (nano)) and cryorolling on aging behavior and mechanical properties of bulk ultrafine grained (UFG) AA6063/4 wt%SiC composites produced via a hybrid route of stir casting and cryorolling. Aging of UFG composites was carried out at different temperatures in the range of 100 °C–175 °C. The results showed that decrease in SiC particle size accelerated the age hardening kinetics and the maximum age hardening effect was observed at 150 °C. The enhancement in age hardening kinetics is attributed to the presence of high dislocation density due to the (i) difference in coefficient of thermal expansion between SiC particles and matrix alloy and (ii) statistically stored dislocation during deformation. Also, the precipitation behavior in UFG composites is established and the microstructural characterization showed the accelerated precipitation kinetics in UFG nano composite. The enhanced age hardening kinetics ultimately improved the strength of the UFG composites compared to UFG base alloy. Among the UFG composites, UFG nano composite showed highest age hardening effect. The overall increase in strength in UFG nano composite is due to the dominant effect of precipitation, dislocation, and grain boundary strengthening mechanisms. © 2019

Aging behavior of ultrafine-grained AA6063/SiC composites with varying reinforcement sizes

Magnesium matrix in-situ composites with hybrid TiC+TiB2 reinforcement are potential materials for automobile and aerospace applications. It is essential to establish the processing map of such composites as these materials may undergo several thermo-mechanical processes while manufacturing engineering components. In the current work, AZ91 Magnesium matrix TiC+TiB2 reinforces hybrid in-situ along with its base counterpart were developed and subjected to solutionization followed by peak aging treatment. The safe processing zone for both base and in-situ composite at all heat treatment conditions have been established through processing map based on dynamic materials model (DMM) by conducting hot compression tests at various temperatures (250 °C – 450 °C) and strain rates (0.001 s−1 – 10 s−1). Two regions: stable and instable were identified from processing map for all the material conditions. Dynamic recrystallization is the main dominant mechanism in stable region, whereas instable region is characterized by twin and intergranular cracks. To understand the mechanism of hot deformation behavior, activation energy is calculated based on constitutive model for all material conditions. The developed in-situ composite in peak aged condition is found to possess higher activation energy (∼230 kJ/mol) as compared to base alloy (∼126 kJ/mol). A correlation between constitutive model and processing map have been established with an emphasis on their microstructures. © 2018 Elsevier B.V.

Journal of Alloys and Compounds

Deformation behavior and processing map development of AZ91 Mg alloy with and without addition of hybrid in-situ TiC+TiB2 reinforcement

The bulk ultrafine grained (UFG) AA6063/4 wt.%SiC composite sheets with varying reinforcement size of SiC (12 μm (coarse), 1 μm (fine) and 45 nm (nano)) have been developed with a novel hybrid process of stir casting and cryo-severe plastic deformation process (cryorolling). The influence of SiC particle size during development of UFG composites and its effect on microstructural modification, strengthening mechanism and failure mechanism was studied in detail. The resultant effect of cryorolling and size of SiC particles has resulted in significant microstructural refinement (less than 350 nm in all UFG composites) and accumulation of high dislocation density; which resulted in improvement in tensile strength as 88%, 108% and 141% in UFG composites reinforced with coarse, fine and nano particles respectively as compared to the unreinforced base alloy. A good agreement in theoretical and experiment yield strength of UFG coarse and fine composites is observed with a variation in UFG nano composite. © 2018 Elsevier B.V.

Development and strengthening mechanisms of bulk ultrafine grained AA6063/SiC composite sheets with varying reinforcement size ranging from nano to micro domain

Cast Al-Si alloys are used for automotive applications. Friction stir processing (FSP) is being used in recent years to improve the performance of these alloys. Secondary machining operations are highly essential on friction stir processed materials to improve the surface finish. However, machinability of friction stir processed cast alloys has rarely been reported. The influence of friction stir processing on microstructure, mechanical properties and machinability of a cast Al-Si alloy was studied in the present work. The main objective is to correlate the metallurgical and mechanical characteristics to the machinability of the friction stir processed material. The age hardening response of as received cast alloy and friction stir processed alloy on machinability and mechanical behavior was also investigated. The strength, ductility and machinability of friction stir processed alloy before and after age hardening treatment were observed to be higher than that of as received cast alloy. The significant improvement in properties of friction stir processed alloy is due to elimination of porosity, formation of fine recrystallized grain structure, homogenization of silicon particles and dissolution of iron rich intermetallics. © 2015 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.

Journal of Manufacturing Processes

Enhancing strength, ductility and machinability of a Al-Si cast alloy by friction stir processing

The microstructure, mechanical properties and fracture behavior of an as-received QE22 alloy have been investigated under different thermal conditions, including solution treated (ST), under aged (UA), peak aged (PA) and over aged (OA) conditions. A significant increase in hardness of 27%, yield strength of 60% and ultimate tensile strength of 19% was observed in peak aged sample as compared to solution treated sample. The improvements of mechanical strength properties are mainly associated with the metastable λ and β' precipitates. Grain growth was not observed in the ST samples after subjecting to UA and PA treatments due to the presence of eutectic Mg12Nd particles along the grain boundaries. In over aged sample, significant grain growth occurred because of dissolution of eutectic phase particles. Different natures of crack initiation and propagation were observed under different thermal conditions during tensile testing at room temperature. The mode of failure of solution treated sample is transgranular, cleavage and twin boundary fractures. A mixed mode of transgranular, intergranular, cleavage and twin boundary failure is observed in both peak aged and over aged samples. © 2015.

Fulltext

Journal of Magnesium and Alloys

Age hardening, fracture behavior and mechanical properties of QE22 Mg alloy

Friction stir processing (FSP) is emerging as an effective tool for microstructural modification and property enhancement. As-cast AZ91 magnesium alloy was friction stir processed with one-pass and two-pass to examine the influence of processing conditions on microstructural evolution and corresponding mechanical properties. Grain refinement accompanied with development of strong basal texture was observed for both processing conditions. Ultrafine-grained (UFG) AZ91 was achieved under two-pass FSP with fine precipitates distributed on the grain boundary. The processed UFG AZ91 exhibited a high tensile strength of ∼435 MPa (117 pct improvement) and tensile fracture elongation of ∼23 pct. The promising combination of strength and ductility is attributed to the elimination of casting porosity, and high density of fine precipitates in an UFG structure with quite low dislocation density. The effects of grain size, precipitate, and texture on deformation behavior have been discussed. © 2013 The Minerals, Metals & Materials Society and ASM International.

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Achieving high strength and high ductility in friction stir-processed cast magnesium alloy

Frontiers in Materials Processing, Applications, Research and Technology

Synthesis of Superhard Lightweight Composites and Improvement of Their Properties via Chemical Processing

Materials Science and Engineering: A

Evolutions of microstructure and mechanical properties for Mg-Al/AlN composites under hot extrusion

Synthesis, characterization and mechanical properties of in-situ (TiC-TiB2) reinforced magnesium matrix composite

Journal	Data powered by TypesetMaterials and Design
Publisher	Data powered by TypesetElsevier Ltd
ISSN	02641275
Open Access	No