Jayant Jain

Double tensile twinning in a Mg–8Al–0.5Zn alloy

The presence of deformation twinning in magnesium introduces significant challenges for predicting the bulk response of the material. In this work, we present results showing the presence of tensile twins formed within pre‐existing tensile twins in samples deformed in compression at 77 K. Such double twins mirror the observation of double compression‐tension twins previously observed. It is argued that the observed double twinning occurs due to the difficulty of non‐basal slip at the low test temperature.

Influence of load, sliding speed, and microstructure on wear response of AZ91 Mg alloy:

This article deals with the tribological study of solution-treated and peak aged AZ91 Mg alloy. Tribological studies were carried out using reciprocating sliding contact under lubricated conditions. The effect of load, sliding speed, and microstructure on wear response of AZ91 Mg alloy was investigated. The wear response was characterized using optical microscopy, scanning electron microscope, and energy dispersive X-ray spectroscopy mapping. The peak aged alloy showed excellent wear resistance against Al6351 Al alloy as compared with solution-treated alloy. The formation of γ-Mg17Al12 precipitates in aged sample was found to increase the wear resistance. The specific wear rate for peak aged alloy was almost one-third than that of solution-treated alloy. In both the samples, i.e. solution-treated and peak aged, the coefficient of friction decreases with increase in sliding speed at low load, while the behavior of peak aged sample was found to be opposite at higher load. At low load, the wear mode for peak aged sample was oxidative which further shifted to adhesive at higher loads.

Investigation of stress relaxation mechanisms for ductility improvement in SS316L

Abstract Stress relaxation during plastic deformation has been reported to improve ductility and alter the mechanical properties of metallic materials. The aim of the present study is to investigate the role of various mechanisms responsible for this in stainless steel SS 316L. The fractography of the tested samples is analysed using an image analyser and the void fraction at failure is correlated with the corresponding mechanisms. The parametric studies on stress relaxation at different pre-strain and relaxation time correlate well with the fractography results supporting the proposed mechanisms. TEM investigation of dislocation structures and void characterisation further confirm the role of dislocation annihilation. Moreover, a novel indentation technique combining micro- and nano-indentation techniques is used to verify the role of stress homogenisation mechanism.

Investigations of wear response of pure Mg and Mg-0.4 Ce-Y2O3/ZnO nano composites using a single and repeated scratch tests

ABSTRACT This work examines the micrometer-scale wear behavior of pure Mg and its composites at various loads (100–500 mN) under single and multiple scratch conditions. The Mg-0.4Ce alloy reinforced with nanoparticles of zinc oxide (ZnO) and yttrium oxide (Y2O3) is investigated. The effect of reinforcement addition on wear characteristics and the coefficient of friction (COF) was evaluated. Moreover, the influence of number of scratches on wear quantification and wear mechanism was deduced at different loads. The results suggest that both the mechanical and tribological performance of ZnO-reinforced composite is significantly better than that of the Y2O3-reinforced composite, which can be attributed to a low COF and higher strengthening due to ZnO addition.

A Study on Mechanical and Tribological Behavior of Brake Pad Materials

Controlled friction and wear are the prime requirements of a braking system. The generation of wear debris depends on the brake materials properties, which in turn controls the tribological behavior. Present study deals with the performance evaluation and failure analysis of two commercial brake pads. Tribo Testing Rig (TTR) was used to evaluate the performance of brake. The tests were performed by making a tribo-pair of brake pad against the rotating disc with varying speed and pressure conditions. The wear response was quantified by mass loss, while the friction was measured in terms of coefficient of friction. Virgin and worn surfaces were analyzed using X-ray diffractometer (XRD), energy dispersive spectroscopy (EDAX) and Scanning electron microscope (SEM) to understand the wear and friction mechanisms. It was found that the type of constituents present in the brake-pad material and their spatial distribution plays an important role in controlling the wear and friction behavior. The high wear and friction was attributed to the presence of bulky particles of Fe and Si.

Tribological Study of Heat Treated AZ91 Alloy against Al6351 under Dry Conditions

AZ91 Mg alloy is one of the most suitable alloy of magnesium for automotive and aerospace applications. In this study, tribological evaluation of AZ91 Mg alloy is performed against Al6351 alloy under dry sliding condition. The load was kept constant for a range (0.05-0.2 m/s) of sliding velocities. This study can be seen as an initial attempt in the direction of employment of Mg alloy for a dynamic engine component. The experiments were conducted on the solution treated and peak aged AZ91 Mg alloy by making a tribo pair with Al6351 alloy on a pin on disc setup under dry condition. The AZ91 and Al6351 alloys were used as a pin and a disc (flat) materials, respectively. The samples were characterized using hardness tester, tribometer and SEM/EDS. The wear mechanisms were identified by analyzing the worn surfaces and wear debris using SEM.