Manganese segregation and intergranular fracture in gamma-based titanium aluminides

Journal Article · Fri Jul 01 00:00:00 EDT 1994 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(94)90096-5· OSTI ID:7289342

Soboyejo, W O; Lou, K ^[1]; McConnell, M ^[2]

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1. Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering
2. General Electric Co., Schenectady, NY (United States). Corporate Research and Development Center

Soboyejo and Lou demonstrated that integranular fracture is induced at an elevated temperature by the segregation of sulfur to the grain boundaries of a binary (Ti-48Al), powder metallurgy, gamma-based titanium aluminide intermetallic that was fractured in-situ in an Auger chamber at 800 C. However, although the possible segregation of other elements had been observed, the authors did not anticipate the importance of Mn segregation at the start of this study. In fact, the original goal of the current investigation was to study the effects of ternary alloying with 1--2% Mn on fatigue and fracture properties, using experimental techniques described in detail in cited references. Mn was only chosen as a ternary alloying element, since it is commonly used to improve the ductility of gamma alloys. Nevertheless, the early studies indicated the predominance of intergranular fracture in ternary Mn-containing gamma alloys that were deformed to failure at room-temperature, where fracture is typically observed to occur by cleavage or quasi-cleavage mechanisms in most gamma alloys. The high incidence of intergranular fracture was also observed to increase with increasing Mn content and annealing duration/temperature in the early studies; such observations led to strong suspicions of S segregation phenomena, which the authors thought might be associated with the high affinity of the Mn starting stock for S. In-situ Auger fracture experiments were therefore carried out on a ternary Mn-containing gamma alloy (Ti-48Al-2Mn) to investigate the possible role of S segregation in the inducement of intergranular fracture in such alloys at room-temperature. Sulfur segregation was observed, as expected. However, the levels of S that were detected on the grain boundary facets were much lower than the Mn levels that were detected on the same grain boundaries. The current paper presents very strong but somewhat unexpected results of Mn segregation in gamma titanium aluminides.

• OSTI ID: 7289342
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 31:1; ISSN 0956-716X; ISSN SCRMEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103* -- Metals & Alloys-- Mechanical Properties
ALLOY SYSTEMS
ALLOYS
ALUMINIUM ALLOYS
DATA
ELEMENTS
EXPERIMENTAL DATA
FRACTURE PROPERTIES
GRAIN BOUNDARIES
INFORMATION
MANGANESE
MANGANESE ALLOYS
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
NONMETALS
NUMERICAL DATA
SEGREGATION
SULFUR
TERNARY ALLOY SYSTEMS
TITANIUM ALLOYS
TRANSITION ELEMENTS