Cryogenic systems have played a crucial role in almost all of the finest technological achievements of mankind. Cryogenic applications demand materials with a unique combination of properties, which drastically limits the choice of materials. In most other engineering applications, because of wide tailorability of their properties and excellent combination of strength and toughness, coupled with lower cost compared with nonferrous materials, steels have become the preferred/dominant structural material for cryogenic applications. The contradictory requirement of higher strength without compromising toughness at cryogenic temperatures posed considerable challenges and led to the development of large array of steels tailored for specific applications. This review is an attempt to survey the metallurgical aspects, material selection, mechanical property evaluation, and application of various standard and nonstandard steels for cryogenic applications. This review covers the influence of low temperatures on material properties, simulative mechanical tests for property evaluation, metallurgy of steels, and application examples surveying the published literature to date. The review also analyzes the origins of low-temperature toughness, various application requirements, and the work carried out at authors’ laboratories. The issues pertaining to mechanical tests at low temperatures and status of data generation in international scenario have been critically analyzed. Physical metallurgy aspects have been highlighted in the review, and microstructure-property-processing correlations for various steels have also been covered. One of the recent advances in steels for cryogenic applications, high-entropy alloys, which are proposed as alternatives for the conventional steels, have been reviewed, and mechanical property data have been critically analyzed. The potential of additive manufactured steels for low-temperature applications has been reviewed. Finally, this review article discusses challenges in processing–mechanical properties correlation for various grades of steels for cryogenic applications. It also provides useful information for researchers working on steels for cryogenic applications with a glimpse of recent advances made in this area.

No abstract

No abstract

Ti-6Al-4V alloy is widely used in Aerospace applications owing to its high specific strength, low coefficient of thermal expansion and good corrosion resistance. Presence of interstitial elements in the alloy has some significant effects on its properties. However the poor notch toughness and cryogenic ductility restricts the usage of Ti-6Al-4V for temperatures lower than 77 K (-196 °C). The Extra Lower Interstitial grade alloy was developed in order to improve the notch toughness and cryogenic ductility of the Ti-6Al-4V alloy. In this refined grade, the interstitials, Oxygen and Carbon are controlled to a maximum limit of 0.12% and 0.08% respectively as compared to a maximum of 0.2% and 0.1% of standard Ti-6Al-4V alloy. In this study, the ELI grade of Ti-6Al-4V rods from three different manufacturing sources were subjected to tensile test at liquid hydrogen temperature at 20 K (-253 oC). The tensile properties obtained are compared and analyzed. The obtained ductility at 20 K is observed to have close relation with the chemical composition and interstitial content and compared with the Ti5Al2.5Sn-ELI which is ideally suitable for low temperatures upto 20 K, owing to its single phase HCP structure. A correlation has been made between the ductile properties and microstructure. By close control of chemical composition and mechanical working, Ti6Al4V-ELI can be used for temperatures lower than 77 K (-196 oC), which is otherwise is forbidden. This paper details the test data obtained from three different compositions of Ti6Al4V-ELI at 20 K, which enables the usage of this material for temperatures lower than 77 K (-196 °C) upto 20 K.

Ti-5Al-2.5Sn alloy is widely used in aerospace applications due to its high specific strength, low coefficient of thermal expansion and good corrosion resistance. Presence of interstitial elements in the alloy has some significant effects on its properties. However the high notch toughness and cryogenic ductility attracts the usage of Ti-5Al-2.5Sn for usage at cryogenic temperatures even at 20K. For hydrogen embrittlement studies and for investigating notch sensitivity of Ti-5Al-2.5Sn alloy, the notched and smooth specimens from ELI grade of Ti-5Al-2.5Sn alloy were subjected to LH2exposure and tensile test at 20K (-253°C) and at 77K (-196°C). The tensile properties obtained from different specimens were compared and analyzed. Also the notch to smooth tensile strength ratio (NSR) were compared and analysed. The obtained NSR was above unity which confirms the low notch brittleness. The tensile strength values between LH2exposed and unexposed specimen at 20K and 77K were compared and it revealed greater compatibility of Ti-5Al-2.5Sn-ELI with liquid hydrogen environment.