Accession Number : AD0489458

Title :   THERMOCHEMICAL TREATMENTS APPLIED TO ULTRA-HIGH STRENGTH STEELS.

Descriptive Note : Quarterly rept. no. 3, 1 May-31 Jul 66,

Corporate Author : MANLABS INC CAMBRIDGE MA

Personal Author(s) : Kalish, D. ; Kulin, S. A.

Report Date : AUG 1966

Pagination or Media Count : 46

Abstract : Ausforming 9-4-45 just above the A sub 1 temperature gave the highest and most reproducible improvement in strength. Significant improvements in strength were produced by ausforming 9-4-25 in the metastable austenite bay region. The increase in strength appears to saturate at 50% deformation. The ratio of longitudinal to transverse fracture toughness (in terms of impact energy and K sub Ic continuously increases as the ausforming rolling deformation increases from 0 to 71% reduction in thickness. The total strengthening achieved by combining ausforming and strain tempering treatments in 9-4-25 was found to be equal to the sum of the strength increases achieved by employing these processes individually. Measurements of K sub Ic were made for six material conditions (yield strengths from 180,000 to 260,000 psi) by five different test methods. The methods involved large scale notch bend specimens, precracked Charpy specimens, and side notched Charpy specimens. There was good agreement among the five test methods. In particular, the side notched Charpy specimen tested by slow bending and measuring the total energy for fracture proved to be an excellent method for evaluating K sub Ic. A dislocation-trapping model is proposed for the mechanism of strain tempering. The creation of dislocations by deformation results in an immediate stress induced ordering about the dislocation line of the carbon atoms existing within a critical interaction radius. (Author)

Descriptors :   *STEEL), (*HOT WORKING, METALLOGRAPHY, AUSTENITE, TRANSITION TEMPERATURE, DEFORMATION, ROLLING(METALLURGY), STRAIN HARDENING, MARTENSITE, MICROSTRUCTURE, NICKEL ALLOYS, COBALT ALLOYS, MECHANICAL PROPERTIES, IMPACT TESTS, NOTCH TOUGHNESS, HEAT TREATMENT.

Subject Categories : Properties of Metals and Alloys
      Fabrication Metallurgy

Distribution Statement : APPROVED FOR PUBLIC RELEASE