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Title: Method for thermal processing alumina-enriched spinel single crystals

A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly.
Inventors:
 [1]
  1. (Aiken, SC)
Issue Date:
OSTI Identifier:
869876
Assignee:
United States of America as represented by United States (Washington, DC) SRS
Patent Number(s):
US 5413973
Contract Number:
AC09-76SR00001
Research Org:
E I DUPONT DE NEMOURS & CO INC
Country of Publication:
United States
Language:
English
Subject:
method; thermal; processing; alumina-enriched; spinel; single; crystals; process; age-hardening; alumina-rich; magnesium; aluminum; obtain; desired; combination; characteristics; hardness; clarity; flexural; strength; toughness; comprises; selection; time-temperature; pair; isothermal; heating; followed; quenching; selected; region; precipitate; sought; crystal; isothermally; heated; pass; phase; pre-precipitates; metastable; precipitates; stable; secondary; matrix; slowly; avoid; shock; rapidly; thermal shock; single crystal; single crystals; single phase; thermal processing; comprises selection; flexural strength; thermal heat; heating followed; phase precipitate; /501/

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