Record Details
Effects of selected minor alloying additions on the structure deformation characteristics of beryllium
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Effects of selected minor alloying additions on the structure deformation characteristics of beryllium |
| Names |
Dooley, George Joseph, III
(creator) McMullen, William D. (advisor) |
| Date Issued | 1969-05-07 (iso8601) |
| Note | Graduation date: 1969 |
| Abstract | Solid solution alloying was employed in an attempt to produce some relatively ductile form of beryllium. If the c/a ratio could be significantly altered, it was felt new or different slip systems could be activated. The following elements were selected on the basis of atomic size, melting point, crystal structure and density for adding to beryllium in amounts of 0.5, 1.0, 2.0, 3.0, 4.0, 5.0 and 10.0 atomic percentages: boron, manganese and, titanium. All samples were non-consumable arc melted, machined and sectioned for wet chemical, spectrographic, X-ray diffraction and metal-lographic analysis as well as for mechanical (compression) testing. These tests showed all alloy samples exceeded the solubility limits in each respective system. Be₄₋₅B, Be₈Mn and Be₁₂Ti were identified as the second phases in the individual systems. Beryllium-boron alloys exhibited an eutectic or peritectic reaction and the eutectic composition in the beryllium-manganese system was established at 22.0 weight percent manganese. The samples Be /0.5B, Be /1.0Mn and Be /0.5Ti gave yield strengths of 47,200 psi, 56,600 psi and 81,250 psi respectively in compression testing. These same specimens yielded work hardening rates of 1.07 x 10⁶ psi, 1.3 x 10⁶ psi and 1.52 x 10⁶ psi respectively. Long wide twins in pure beryllium were accompanied by large amounts of cross-slip. The boron sample displayed long wide twins and also very short narrow twins, no cross-slip and extensive areas with microcracks present. Shorter and narrower twins characterize the manganese specimens. The beryllium-titanium alloys exhibited extremely small twins emanating from particles of second phase Be₁₂Ti; however, the majority of the twins in this system are long, extremely narrow and are seen to be internally constricted along the length of the twin. These constrictions have been ascribed to a strain relief process which further prevented the twin from growing parallel to its shorter dimension. The near total absence of cross-slip in the three alloy systems was attributed to a lessening of the stacking fault energy as a result of increasing the solute concentration. The drop in the stacking fault energy decreases the probability for cross-slip, makes extensive deformation difficult and explains higher yield strengths and work hardening rates. Evidence presented suggests slip occurs prior to gross twin propagation. The relationship between twinning shear and twin shape suggests for the beryllium-titanium alloys twinning on higher order planes (e.g., {.1121} or 11122 }) rather than the {1012} twinning normally observed. |
| Genre | Thesis/Dissertation |
| Topic | Beryllium -- Analysis |
| Identifier | http://hdl.handle.net/1957/47328 |
