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.

Sushanta Kumar Panigrahi

Department of Mechanical Engineering

AS-CAST AZ91 MAGNESIUM ALLOYS

Deformation behavior

Friction stir processing

HIGH STRENGTH AND HIGH DUCTILITIES

HIGH-TENSILE STRENGTH

Low-dislocation density

MICROSTRUCTURAL MODIFICATION

STRENGTH AND DUCTILITIES

Ductility

Grain boundaries

Grain refinement

Grain size and shape

Precipitates

Textures

Magnesium 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

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

The disposal of used automobiles tyres is a major environmental concern of the day. Annually, there are 1.2 billion tyres seeking disposal issues globally. Concrete as a major construction material can potentially adopt processed rubber waste—derived from tyres as a partial replacement for aggregates. The present study is focused on mechanical and thermal properties of concretes with rubber as partial replacement to well-graded conventional aggregates. The study includes replacement of 10, 20, 30 and 100% of coarse aggregate with waste tyre aggregates and was compared with conventional M30 grade concrete. Concretes were subjected a thermal cyclic heating of 50 °C for a period of 7 days. The results showed that the weight of the rubber concrete is reduced by 12% compared to the conventional concrete and the strength of the concrete reduces with the increase in rubber content. At ambient temperatures, the rubber concrete was found thermally stable. The compressive strengths were found increasing after cyclic heating of 50 °C for a period of 7 days. This effect may be due the effect of Portland pozzolana cement which has 30% of fly ash in it. From this study, it can be concluded that rubber waste concretes can be a potential candidate for structural and non-load bearing structures at ambient temperatures. © 2019, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

On Mechanical and Thermal Properties of Concretes with Rubber as Partial Replacement to Well-Graded Conventional Aggregates

A commercial magnesium alloy was processed through multi-pass and multi-directional (unidirectional, reverse, and transverse tool movements) friction stir processing (FSP). Based on the FSP location, the dominant prior-deformation basal texture was shifted along the arc of a hypothetical ellipse. The patterns of deformation texture developments were captured by viscoplastic self-consistent modeling with appropriate velocity gradients. The simulated textures, however, had two clear deficiencies. The simulations involved shear strains of 0.8 to 1.0, significantly lower than those expected in the FSP. Even at such low shear, the simulated textures were significantly stronger. Microstructural observations also revealed the presence of ultra-fine grains with relatively weak crystallographic texture. Combinations of ultra-fine grain superplasticity followed by grain coarsening were proposed as the possible mechanism for the microstructural evolution during FSP. © 2016, The Minerals, Metals &amp; Materials Society and ASM International.

Microstructural Evolution During Multi-Pass Friction Stir Processing of a Magnesium Alloy

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

Materials and Design

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

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

A commercial magnesium alloy was processed through multi-pass and multi-directional (unidirectional, reverse, and transverse tool movements) friction stir processing (FSP). Based on the FSP location, the dominant prior-deformation basal texture was shifted along the arc of a hypothetical ellipse. The patterns of deformation texture developments were captured by viscoplastic self-consistent modeling with appropriate velocity gradients. The simulated textures, however, had two clear deficiencies. The simulations involved shear strains of 0.8 to 1.0, significantly lower than those expected in the FSP. Even at such low shear, the simulated textures were significantly stronger. Microstructural observations also revealed the presence of ultra-fine grains with relatively weak crystallographic texture. Combinations of ultra-fine grain superplasticity followed by grain coarsening were proposed as the possible mechanism for the microstructural evolution during FSP. © 2016, The Minerals, Metals & Materials Society and ASM International.

Advanced Materials

Masthead: (Adv. Mater. 33/2018)

Materials Science and Engineering: A

Grain size and texture effects on deformation behavior of AZ31 magnesium alloy

Scripta Materialia

Exceptionally high strength in Mg–3Al–1Zn alloy processed by high-ratio differential speed rolling

Influence of grain size and texture on Hall–Petch relationship for a magnesium alloy

Effect of texture on the mechanical behavior of ultrafine grained magnesium alloy

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

Journal	Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
ISSN	10735623
Open Access	No