Bhagwati Prasad Kashyap

Bio: Bhagwati Prasad Kashyap is an academic researcher from Indian Institute of Technology Bombay. The author has contributed to research in topics: Strain rate & Superplasticity. The author has an hindex of 31, co-authored 148 publications receiving 2796 citations. Previous affiliations of Bhagwati Prasad Kashyap include University of Manitoba & University of California, Davis.

On the hot workability of eli grade titanium alloy Ti-6Al-4V

Abstract: Using the test data of extra low interstitial (ELI) grade titanium alloy Ti-6Al-4V (wt.%) with microstructural observations, studies are made to examine the flow localization concepts as well as the simplified metallurgical stability criterion for delineating the regions of flow instabilities in the processing maps. The optimum hot working conditions for the material are suggested.

Variation in tensile ductility and terminal microstructure of the binary two-phase Al-Cu alloys at elevated temperatures

Abstract: Tensile specimens of the Al-Cu alloys containing 5.6 to 33.4 wt.% Cu were deformed to failure for investigating the effects of strain rate, test temperature, initial grain size and the volume fraction of θ phase on ductility, grain growth and cavitation level. The ductility increases with the increase in temperature and decrease in grain size. The other variables, however, influence the ductility more in an interdependent manner. There occur grain growth and cavitation to varying extent depending on test condition; but the latter appears to show a systematic effect in limiting the ductility.

Temperature-Dependent Flow Behavior and Microstructural Evolution During Compression of As-Cast Mg-7.7Al-0.4Zn

Abstract: The microstructure and mechanical properties improve substantially by hot working. This aspect in as-cast Mg-7.7Al-0.4Zn (AZ80) alloy is investigated by compression tests over temperature range of 30-439°C and at strain rates of 5 × 10−2, 10−2, 5 × 10−4 and 10−4 s−1. The stress exponent (n) and activation energy (Q) were evaluated and analyzed for high-temperature deformation along with the microstructures. Upon deformation to a true strain of 0.80, which corresponds to the pseudo-steady-state condition, n and Q were found to be 5 and 151 kJ/mol, respectively. This suggests the dislocation climb-controlled mechanism for deformation. Prior to attaining the pseudo-steady-state condition, the stress-strain curves of AZ80 Mg alloy exhibit flow hardening followed by flow softening depending on the test temperature and strain rate. The microstructures obtained upon deformation revealed dissolution of Mg17Al12 particles with concurrent grain growth of α-matrix. The parameters like strain rate sensitivity and activation energy were analyzed for describing the microstructure evolution also as a function of strain rate and temperature. This exhibited similar trend as seen for deformation per se. Thus, the mechanisms for deformation and microstructure evolution are suggested to be interdependent.

Texture Evaluation in Zr-2.5 % Nb Pressure Tubes Using Kearn’s f Parameter

Abstract: The anisotropic properties of Zr-2.5 wt % Nb pressure tube material, used in pressurized heavy water reactors (PHWR) depend primarily on the texture associated with the material. Particularly properties such as coefficient of thermal expansion, mechanical anisotropy, irradiation growth, stress corrosion cracking, and delayed hydrogen cracking, are directly correlated. Thus, the knowledge of preferred orientation becomes an essential prerequisite for property evaluation. In the present paper the correlation between the preferred orientation factor, namely Kearn’s f′ parameter, and some of the important properties of the material is summarized. The f parameters were deduced from the X-ray diffraction data, using the inverse pole figure method, and then subsequently the values were verified experimentally using the direct pole figure method.

Effect of cold working and annealing on grain size and hardness of a Zr-2.5Nb alloy

Abstract: Samples of Zr-2.5 wt.% Nb alloy, obtained from pressure tube, were annealed in the temperature range 700-900 °C up to 100 h to investigate the grain growth behaviour. The grain size increases with annealing time (t) and temperature (T) according to the relationship d t 0.21 exp((-387 kJ/mol)/RT). Room temperature hardness increases with the increasing annealing temperature and grain size, which is ascribed to the transformation of β-phase into martensitic α' and the substructure developed during quenching. The grain sizes, produced by further cold working and annealing for short time (< 1 h), and the corresponding hardness values, however, support the Hall-Petch type relationship in the limited cases.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Mechanical Behavior of Materials

Abstract: A balanced mechanics-materials approach and coverage of the latest developments in biomaterials and electronic materials, the new edition of this popular text is the most thorough and modern book available for upper-level undergraduate courses on the mechanical behavior of materials To ensure that the student gains a thorough understanding the authors present the fundamental mechanisms that operate at micro- and nano-meter level across a wide-range of materials, in a way that is mathematically simple and requires no extensive knowledge of materials This integrated approach provides a conceptual presentation that shows how the microstructure of a material controls its mechanical behavior, and this is reinforced through extensive use of micrographs and illustrations New worked examples and exercises help the student test their understanding Further resources for this title, including lecture slides of select illustrations and solutions for exercises, are available online at wwwcambridgeorg/97800521866758

Recent developments in stainless steels

Abstract: This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Additively manufactured hierarchical stainless steels with high strength and ductility

Abstract: Many traditional approaches for strengthening steels typically come at the expense of useful ductility, a dilemma known as strength-ductility trade-off. New metallurgical processing might offer the possibility of overcoming this. Here we report that austenitic 316L stainless steels additively manufactured via a laser powder-bed-fusion technique exhibit a combination of yield strength and tensile ductility that surpasses that of conventional 316L steels. High strength is attributed to solidification-enabled cellular structures, low-angle grain boundaries, and dislocations formed during manufacturing, while high uniform elongation correlates to a steady and progressive work-hardening mechanism regulated by a hierarchically heterogeneous microstructure, with length scales spanning nearly six orders of magnitude. In addition, solute segregation along cellular walls and low-angle grain boundaries can enhance dislocation pinning and promote twinning. This work demonstrates the potential of additive manufacturing to create alloys with unique microstructures and high performance for structural applications.