Accession Number : ADA019461

Title :   Improvement of Fatigue Properties in Titanium Alloys.

Descriptive Note : Technical rept.,

Corporate Author : GEORGE WASHINGTON UNIV WASHINGTON D C SCHOOL OF ENGINEERING AND APPLIED SCIENCE

Personal Author(s) : Gilmore,Charles M. ; Imam,M. Ashraf

Report Date : AUG 1974

Pagination or Media Count : 48

Abstract : The fatigue crack initiation lives of annealed Ti-6Al-4V alloys were determined at low (+ or - 0.006 in/in) and high (+ or - 0.012 in/in) shear strain amplitudes. The initiation life was separated from the propagation life by determining when extensive axial elongation of the specimen occurred. At 0.006 and 0.012 strain amplitudes the a-b annealed (alpha beta A) and mill annealed (MA) specimens have similar lives to crack initiation followed by recrystallized anneal (RA) and beta annealed (beta A) specimens. Analysis of the beta A specimens showed that structure related fatigue fracture was occurring and this was not observed with the other anneals. 'Cyclic creep' tests were conducted on each anneal treatment and the RA material exhibited the best dimensional stability and the beta A material the worst. These results are in accordance with the expected phase stability of each alloy; the RA material should be the closest to an equilibrium microstructure; the Beta A material the farthest from an equilibrium microstructure. The greatest increase in fatigue lives occurred for specimens quenched from a solution temperature of 1650 F, which is about 100 F below the beta transus. Reduction of solution temperature to 1550 F, or increases to 1750 F and 1950 F resulted in lower lives than the 1650 F solution temperature. The fracture surface of the material quenched from 1950 F had brittle type fatigue striations, also the region of fast fracture had evidence of microstructure effects. (Author)

Descriptors :   *Titanium alloys, *Fatigue(Mechanics), *Fracture(Mechanics), *Cracking(Fracturing), Fatigue life, Titanium, Cracks, Crack propagation, Annealing, Quenching, High temperature, Metallurgy, Microstructure

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE