Accession Number : ADA020021

Title :   Research Toward High Strength High Toughness Steels.

Descriptive Note : Final rept. Mar 73-Feb 75.


Report Date : SEP 1975

Pagination or Media Count : 82

Abstract : Several different ways of microstructural control were attempted in maraging type steels in order to achieve a combination of high strength and high toughness. In Section I, the composition, processing and mechanical properties of Fe-Ni-Ti alloys are described. It is found that high nickel content and high aging temperature are beneficial for toughness. This alloy system, however, does not exhibit high toughness due to the extensive grain boundary precipitation during aging. In Section II, the well-known toughening mechanisms, i.e., grain refinement, retained austenite, and the TRIP mechanism are incorporated to a 250 grade maraging stee. The improvement in fracture toughness is obtained only when the retained austenite remains stable during deformation. The microduplex maraging steel preserves its high fracture toughness upon high strain rate fracture in contrast to most of the martensitic steels. In Section III initial success is reported with an alternate toughening technique: the introduction of a dense mobile dislocation density through rapid phase transformation of a partially maraged structure.

Descriptors :   *Toughness, *Maraging steels, Grain size, Yield strength, Microstructure, Heat treatment, Phase studies

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE