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Indian Institute of Science

1. Patro, Debdutt. Kinetics Of Pressureless Infiltration Of Al-Mg Alloys Into Al2O3 Preforms : A Non-Uniform Capillary Model.

Degree: 2006, Indian Institute of Science

Al-Mg alloys spontaneously infiltrate into porous ceramic preform in a nitrogenous atmosphere above 750 °C with Mg either pre-alloyed or introduced at the interface to initiate the process. The governing process variables are temperature, alloy composition, atmosphere and particle size of the porous preform. The present study investigates the flow kinetics of Al-Mg melts into porous Al2O3 preforms as a function of particle size of the preform from the standpoint of a physical phenomena fluid flow through a non-uniform capillary. Pressureless infiltration involves two major stages: (a) initiation associated with an incubation period and, (b) continuation where the melt infiltrates the preform. Long (~1 hr) and irreproducible incubation periods are typically observed in the Al- Mg/Al2O3 system when the samples are slowly heated in N2 atmosphere. Such lengthy periods prior to infiltration also lead to excessive Mg loss from the system. In order to accurately measure infiltration rates during the continuation stage, the incubation period was minimized by upquenching samples in air under self-sealing conditions. Interrupted experiments reveal that infiltration occurs within 5 mins. Different phenomena are expected to dictate the capillary rise kinetics through the porous ceramic post-incubation (more specifically, retard the melt movement) (a) triple-point ridging of the melt meniscus on the alumina surface (meniscus pinning) (b) interfacial reaction limited wetting and infiltration (c) pore size and distribution of the porous ceramic (d) melt (Al-Mg) / atmosphere (N2) reaction to form products inside the pore space (decrease in permeability) (e) time-dependent loss of Mg from the system (time-dependent contact angle) Some of the above phenomena viz., fluid flow inside the porous medium and chemical reaction of the melt with the reinforcement are invariably coupled in a complex manner. The contribution of each phenomenon to the kinetics of infiltration (a) and (e) was investigated separately. Triple-line ridging Al sessile drops on alumina substrate spread 4-5 orders of magnitude slower than that predicted by hydrodynamic equilibrium. The melt is pinned by ridges leading to spreading rates of 0.4-4 mm/hr in contrast to viscous drag controlled spreading rates of 1-10 mm/sec. In order to detect ridging in the Al-Mg/Al2O3 reactive couple, uniform Al2O3 capillaries were infiltrated. Experiments were conducted under sealed configuration with metal on both sides of the capillary and Mg turnings at the interface. The uniform capillary itself was placed inside an alumina preform and the assembly upquenched to 800-900 °C to minimize evaporative loss of Mg. Examination of the inner walls of the capillary after leaching away the infiltrated metal shows rough, granular features on the polycrystalline Al2O3 surface. No continuous ridges were seen. EDS of the granular phase suggested stoichiometry of spinel, MgAl2O4, formed as a result of the reaction between the melt and the capillary. From interrupted experiments the average… Advisors/Committee Members: Jayaram, Vikram.

Subjects/Keywords: Aluminum-Magnesium Alloys; Al2O3 Preforms; Infiltration Kinetics; Al-Mg Alloys - Infiltration; Sinusoidal Capillary Model; Pressureless Infiltration; Non-Uniform Capillary Model; Metallurgy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Patro, D. (2006). Kinetics Of Pressureless Infiltration Of Al-Mg Alloys Into Al2O3 Preforms : A Non-Uniform Capillary Model. (Thesis). Indian Institute of Science. Retrieved from http://hdl.handle.net/2005/410

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Patro, Debdutt. “Kinetics Of Pressureless Infiltration Of Al-Mg Alloys Into Al2O3 Preforms : A Non-Uniform Capillary Model.” 2006. Thesis, Indian Institute of Science. Accessed December 07, 2019. http://hdl.handle.net/2005/410.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Patro, Debdutt. “Kinetics Of Pressureless Infiltration Of Al-Mg Alloys Into Al2O3 Preforms : A Non-Uniform Capillary Model.” 2006. Web. 07 Dec 2019.

Vancouver:

Patro D. Kinetics Of Pressureless Infiltration Of Al-Mg Alloys Into Al2O3 Preforms : A Non-Uniform Capillary Model. [Internet] [Thesis]. Indian Institute of Science; 2006. [cited 2019 Dec 07]. Available from: http://hdl.handle.net/2005/410.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Patro D. Kinetics Of Pressureless Infiltration Of Al-Mg Alloys Into Al2O3 Preforms : A Non-Uniform Capillary Model. [Thesis]. Indian Institute of Science; 2006. Available from: http://hdl.handle.net/2005/410

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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