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

Sushanta Kumar Panigrahi

Department of Mechanical Engineering

B. N. Sahoo

Abrasives

Magnesium alloys

microstructure

Precipitation (chemical)

Reinforcement

TITANIUM CARBIDE

tribology

Wear of materials

AZ91 MAGNESIUM ALLOYS

DRY SLIDING WEAR

IN-SITU COMPOSITE

MG MATRIX COMPOSITES

MICROSTRUCTURAL CONDITIONS

MICROSTRUCTURAL MODIFICATION

Processing parameters

Wear mechanisms

Titanium alloys

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

Tribology International

This paper described the influence of varying sizes of SiC ceramic reinforcement (coarse (12 μm), fine (1 μm) and nano (45 nm)) in establishing the wear mechanisms and the wear mechanism maps of ultrafine grained (UFG) AA6063/4 wt%SiC composites. The UFG composites were developed by a hybrid manufacturing route of stir casting and cryorolling. The pin-on-disc machine under normal loads of 10–50 N and sliding speeds of 0.5–2 m/s was used to investigate wear behavior. The synergetic effect of cryorolling and varying ceramic reinforcement size has resulted in microstructural modification and has reducing effect on specific wear rate. Microstructural characterization revealed that, cryorolling has accumulated high dislocation density and arrested recovery and recrystallization at liquid nitrogen temperature. Frictional heat generated at wear surface with increase in sliding speed and load has activated the dynamic recovery, recrystallization and precipitation which further increased the hardness and reduced the specific wear rate. The wear mechanisms were established for UFG materials. The wear mechanism maps were constructed and correlated with the microstructures of worn surfaces of UFG materials to identify the dominant wear mechanism. © 2019 Elsevier Ltd and Techna Group S.r.l.

Ceramics International

Influence of SiC ceramic reinforcement size in establishing wear mechanisms and wear maps of ultrafine grained AA6063 composites

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 application of AZ91 magnesium alloy is limited because of dendritic β-Mg17Al12 phase which degrades mechanical properties and causes high tension to compression yield asymmetry (R). To overcome this, a severe plastic deformation (SPD) based hybrid process has been implemented in this study, to develop in-situ AZ91 + TiC-TiB2 composite. This results in redistribution of β-Mg17Al12 phase on the grain boundaries along with notable grain refinement. The combined effect of in-situ reinforcement and grain refinement due to SPD process resulted in simultaneous enhancement of strength and ductility. Further, intense grain refinement and presence of TiC-TiB2 reinforcement in the grain boundary region is found to increase the stress concentration along the grain boundary which hinders twin nucleation and significantly reduces the R value from 1.42 (as-cast condition) to 1.04 (SPDed in-situ composite). The underlying mechanism of significant property enhancement in the developed material has been correlated with the tension and compression tests and microstructures. © 2018 Elsevier B.V.

Materials Science and Engineering A

Microstructural modification and its effect on strengthening mechanism and yield asymmetry of in-situ TiC-TiB2/ AZ91 magnesium matrix composite

The present work aims to study the individual as well as the combined effect of in-situ particles and precipitates on the tension-compression asymmetricity of AZ91 magnesium (Mg) alloy and AZ91 + TiC-TiB2 Mg matrix composites. Investigations have been done on four different material conditions: (a) alloy without particles or precipitates, (b) alloy with precipitates, (c) composite with particles, (d) composites with both particles and precipitates. Both the particle and precipitate significantly contribute towards lowering of tension to compression yield asymmetry. These particles/precipitates increase the critical stress for twinning by exerting a back stress which hinders the twin propagation. Due to decrease in the twinning propensity, the tension to compression asymmetry reduces from 1.30 (at base condition) to 1.04 (peak aged condition of the composite). This phenomenon has been experimentally validated by means of tension and compression tests and the results have been correlated with the pre and post-deformation microstructures. © 2017 Elsevier B.V.

A study on the combined effect of in-situ (TiC-TiB2) reinforcement and aging treatment on the yield asymmetry of magnesium matrix composite

Aluminum-copper alloy system is extensively used in structural and aerospace applications for its high strength-to-weight ratio, good mechanical and tribological properties. Improving the properties of these alloys would likely widen their application area. In the present work, an attempt has been made to simultaneously enhance the wear resistance and mechanical properties of an Al-Cu alloy, AA2014 by imparting different levels of cryorolling strains and postroll aging treatment. The wear behavior of the material is studied under dry sliding condition by pin-on-disk experiments and mechanical properties are assessed by tensile test. Formation of high fraction of dislocation density and significant refinement of microstructure during cryorolling and nucleation of fine coherent Guinier-Preston (GP) zones of Al2Cu precipitates during postcryoroll aging has led to about 100% increment in the wear resistance of the material. Tensile test results proved that the synergetic effect of cryorolling and aging treatment led to 53% increment in strength (557 MPa) without compromising the material's ductility (22.5%). A detailed investigation on the various mechanisms responsible for the enhanced wear resistance and improved mechanical performance is presented based on the microstructural evidence. © 2018 by ASME.

Journal of Tribology

Synergetic Effect of Cryorolling and Postroll Aging on Simultaneous Increase in Wear Resistance and Mechanical Properties of an Al-Cu Alloy

In the present work, influence of in-situ TiC-TiB2 reinforcement on age hardening behavior and mechanical properties of TiC-TiB2/AZ91 composite was investigated. The base and in-situ composite materials were solution treated at 400 °C for 24 h and then aged at different temperatures up to 100 h. The kinetics of age hardening results revealed that the addition of in-situ TiC-TiB2 reinforcement increase the age hardening kinetics of the composite as compared to AZ91 magnesium alloy. The improvement in age hardening kinetics is attributed to the presence of high dislocation density resulted from the mismatch of coefficients of thermal expansion between in-situ TiC-TiB2 reinforcement and magnesium matrix. The precipitation behavior of Mg17Al12 phase in both AZ91 alloy and TiC-TiB2/AZ91 composites were established. After age hardening, base and in-situ composite materials show significant improvement in ultimate tensile strength by 47.72% and 66.49% respectively as compared with the base monolithic alloy. The enhancement of mechanical properties in the base and in-situ composites is explained in detail by analyzing their fractographs and microstructures. © 2018

Materials Characterization

Effect of in-situ (TiC-TiB2) reinforcement on aging and mechanical behavior of AZ91 magnesium matrix composite

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

Journal	Data powered by TypesetTribology International
Publisher	Data powered by TypesetElsevier Ltd
ISSN	0301679X
Open Access	No