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Title: Characteristics of commercial vacuum-hot-pressed beryllium. Summary report

Abstract

The tensile properties of four grades of well-characterized commercial hot-pressed beryllium block were determined at room temperature to 1100 deg F and supplemented with measurements of the strain-rate dependence of one of the materials at 500 to 1100 deg F at strain rates of 0.0355 to 5 per min. The four hot pressings studied were, in general, found to be quite uniform in structural, chemical, and mechanical properties, although significant difference s in uniformity among the four were found. All hot-pressed blocks were found to have densities below theoretical. An initial yield point was found in three of the four materials; it was absent in the metal with the largest grain size. No influence of chemistry on the occurrence of a yield drop was found within the compositional range investigated. The magnitude of the yield drop generally increased with temperature, reaching a maximum at 400 to 700 deg F, and disappeared between 900 and 1100 deg F. It was found to be insensitive to changes in strain rate between 0.0385 and 5 per min. The yield point could be removed by pressurization or heat treatment and made to reappear by heat treatment. Small amounts of preferred orientation were found tomore » have a marked effect on the mechanical behavior at room temperature to 500 deg F. The ductility is especially influenced and leads to a ductile-- brittle transition temperature which differs by approximately 100 deg F in the pressing and transverse directions. Serrated yielding (Portevin--Le Chatelier effect) was found in three of the materials at 900 deg F and a strain rate 0.0355 per min. It was also present at 1100 deg F and 0.5 per min in the one material tested at increased strain rates. Yield and ultimate tensile strengths were found to be relatively insensitive to strain-rate variations over the range from 0.0355 to 5 per min. The ductilities, however, were greatly decreased by an increase in strain rate and the behavior could be interpreted in terms of a shift in the ductile-brittle transition temperature of 150 to 200 deg F. Results of metallographic observation on sections of fractured tensile samples indicated that ultimate failure was caused by the joining of stable cleavage cracks at room temperature, by ductile rupture at 700 deg F, and by intergranular failure caused by void coalescence at 1100 deg F. An increase in yield strength at 300 to 500 deg compared with that at room temperature was found in one of the materials; this is interpreted as evidence of strain aging. This phenomenon has been related to the iron/aluminum ratio and the amount of iron in solid solution. It is concluded that embrittlement could arise from a combination of strain aging, a high initial yield point, excessive preferred orientation, and increased work-hardening rates due to high strain rates. (auth)« less

Authors:
;
Publication Date:
Research Org.:
Battelle Columbus Labs., Ohio (USA)
OSTI Identifier:
4359430
Report Number(s):
BMI-X-629
NSA Number:
NSA-29-010666
DOE Contract Number:  
W-7405-ENG-92
Resource Type:
Technical Report
Resource Relation:
Other Information: Orig. Receipt Date: 30-JUN-74
Country of Publication:
United States
Language:
English
Subject:
N50230* -Metals, Ceramics, & Other Materials-Metals & Alloys-Properties, Structure & Phase Studies; *BERYLLIUM- MECHANICAL PROPERTIES; CHEMICAL COMPOSITION; CHEMICAL PROPERTIES; DENSITY; DUCTILE-BRITTLE TRANSITIONS; FAILURES; GRAIN ORIENTATION; HIGH TEMPERATURE; HOT PRESSING; MEDIUM TEMPERATURE; MICROSTRUCTURE; SOLID SOLUTIONS; STRAINS; TENSILE PROPERTIES; TIME DEPENDENCE

Citation Formats

Gelles, S.H., and Peterson, J.H. Characteristics of commercial vacuum-hot-pressed beryllium. Summary report. United States: N. p., 1970. Web.
Gelles, S.H., & Peterson, J.H. Characteristics of commercial vacuum-hot-pressed beryllium. Summary report. United States.
Gelles, S.H., and Peterson, J.H. Thu . "Characteristics of commercial vacuum-hot-pressed beryllium. Summary report". United States.
@article{osti_4359430,
title = {Characteristics of commercial vacuum-hot-pressed beryllium. Summary report},
author = {Gelles, S.H. and Peterson, J.H.},
abstractNote = {The tensile properties of four grades of well-characterized commercial hot-pressed beryllium block were determined at room temperature to 1100 deg F and supplemented with measurements of the strain-rate dependence of one of the materials at 500 to 1100 deg F at strain rates of 0.0355 to 5 per min. The four hot pressings studied were, in general, found to be quite uniform in structural, chemical, and mechanical properties, although significant difference s in uniformity among the four were found. All hot-pressed blocks were found to have densities below theoretical. An initial yield point was found in three of the four materials; it was absent in the metal with the largest grain size. No influence of chemistry on the occurrence of a yield drop was found within the compositional range investigated. The magnitude of the yield drop generally increased with temperature, reaching a maximum at 400 to 700 deg F, and disappeared between 900 and 1100 deg F. It was found to be insensitive to changes in strain rate between 0.0385 and 5 per min. The yield point could be removed by pressurization or heat treatment and made to reappear by heat treatment. Small amounts of preferred orientation were found to have a marked effect on the mechanical behavior at room temperature to 500 deg F. The ductility is especially influenced and leads to a ductile-- brittle transition temperature which differs by approximately 100 deg F in the pressing and transverse directions. Serrated yielding (Portevin--Le Chatelier effect) was found in three of the materials at 900 deg F and a strain rate 0.0355 per min. It was also present at 1100 deg F and 0.5 per min in the one material tested at increased strain rates. Yield and ultimate tensile strengths were found to be relatively insensitive to strain-rate variations over the range from 0.0355 to 5 per min. The ductilities, however, were greatly decreased by an increase in strain rate and the behavior could be interpreted in terms of a shift in the ductile-brittle transition temperature of 150 to 200 deg F. Results of metallographic observation on sections of fractured tensile samples indicated that ultimate failure was caused by the joining of stable cleavage cracks at room temperature, by ductile rupture at 700 deg F, and by intergranular failure caused by void coalescence at 1100 deg F. An increase in yield strength at 300 to 500 deg compared with that at room temperature was found in one of the materials; this is interpreted as evidence of strain aging. This phenomenon has been related to the iron/aluminum ratio and the amount of iron in solid solution. It is concluded that embrittlement could arise from a combination of strain aging, a high initial yield point, excessive preferred orientation, and increased work-hardening rates due to high strain rates. (auth)},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1970},
month = {1}
}

Technical Report:
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