Strain age embrittlement

In addition to hydrogen embrittlement, brittle failure can occur as a result of stress corrosion, liquid metal attack, or strain-age hardening. The last mentioned cause is well known and can occur on strained steel of any strength but seldom actually occurs in modem steels it is adequately documented in Appendix E of BS 729 (British Standards Institution, 1971 reaffirmed in 1986) users often erroneously refer to this effect as hydrogen embrittlement. This clearly states that strain-age embrittlement is the only type of embrittlement that can be aggravated by the hot dip galvanizing process. 

Severe loss of ductility of a metal (or alloy) loss of load carrying capacity of a metal or alloy the severe loss of ductility or toughness or both, of a material, usually a metal or alloy. Many forms of embrittlement can lead to brittle fracture and many can occur during thermal treatment or elevated-temperature service (thermally induced embrittlement). Some of these forms of embrittlement, which affect steels, include blue brittleness, 885 °F (475 °C) embrittlement, quench-age embrittlement, sigma-phase embrittlement, strain-age embrittlement, temper embrittlement, tempered martensite embrittlement, and thermal embrittlement. In addition, steels and other metals and alloys can be embrittled by environmental conditions (environmentally assisted embrittlement). Forms of environmental embrittlement include acid embrittlement, caustic embrittlement, corrosion embrittlement, creep-rupture embrittlement, hydrogen embrittlement, bquid metal embrittlement, neutron embrittlement, solder embrittlement, sobd metal embrittlement, and stress-corrosion cracking. 

Strain aging can also occur in susceptible steels by welding near a crack, causing embrittlement (called dynamic strain aging). For this and other reasons, many users require that plate material intended for pressure-containing components be scanned by ultrasonic inspection equipment for cracks and flaws near edges to be welded. 

Modification of specifications Adequate investigation adequate experience weldability trials toughness resistance to neutron irradiation strain ageing and thermal embrittlement. 

The inplane shear stress-strain tests reported here have been well demonstrated to be a reliable test for matrix-dominated properties in composites 141). For the selected mechanical properties that were monitored, their sensitivity to the thermal history was well demonstrated. In particular, the embrittlement process during the sub-Tg annealing or physical aging has been clearly observed. This decrease in molecular mobility, which gives rise to an increase in relaxation time and hence a decrease in toughness, can be rationalized as a decrease in free volume in an approach towards the equilibrium glassy state. 

The results of different laboratory tests, suggested during the development of an ISO standard on sealant durability, were compared with those obtained from outdoor weathering under mechanical strain. The comparison revealed that the 70C compression test, as included in ASTM C-719, was helpful in identifying sealants which fail due to high compression set. The heat compression test, however, did not rule out sealants that tend to postcure or embrittle upon ageing. The best correlation was obtained if the sealants were allowed to fully cure prior to laboratory testing. 6 refs. 

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