Multi-principal element alloy, method for preparing the same and uses thereof
The present invention belongs to the sector of metallurgical industry. More particularly, it relates to new multi-principal element alloys, in particular to multi-principal element alloys as cast and heat-treated multi-principal element alloys, as well as to their preparation. These alloys have particular crystallinity properties, such as a dual microstructure which can be modified depending on the use of different cooling rates or a thermal treatment during its preparation. They also have specific mechanical properties, such as intermediate Vickers hardness, high yield and high tensile strength, among others, which would make them particularly suitable for their use as material for hydrogen storage, to which the present invention also relates.
Context
Hydrogen storage requires the use of materials which do not undergo hydrogen embrittlement (HE), which is a reduction in elongation and toughness caused by exposure to hydrogenated environments, more particularly, due to hydrogen dissociation and absorption occurring in the storage material. Furthermore, while hydrogen can be stored in different forms, it is mostly stored in gas or liquid condition, in both cases requiring significantly low-temperature and highpressure conditions. Such low temperatures are also known to require the use of materials with high mechanical resistance, among other particular properties.
While certain austenitic stainless steels (e.g., type 316L austenitic stainless steel) or aluminium alloys may be used for storing hydrogen due to having high resistance to hydrogen embrittlement, they typically have reduced mechanical strength while, at the same time, they are significantly more expensive compared to other steels such as Cr-Mo or Ni-Cr-Mo steels. In parallel, other known steels employed in the construction of structural elements, such as the 42CrMo4 steel, are not adequate for hydrogen storage due to being susceptible to hydrogen embrittlement.
Multi-principal element alloys (MPEAs), including high-entropy alloys (HEAs), are well known alloys with a solid solution hardening mechanism of different elements in the range of near to equiatomic proportion which minimizes the quantity of different phases. There exist evidence of some MPEAs with a major face-centered cubic (FCC) microstructure, such a CoNiV alloys, presenting slightly improved mechanical properties at low temperature in the presence of hydrogen. However, the presence of Co and V in those alloys dramatically increases the cost of the material due to their scarce availability, therefore hindering their use as hydrogen storage solutions at industrial scale.
In this context, it becomes apparent that there exists the need for new metallic materials which offer increased yield strength and tensile strength compared to other types of crystalline materials, without significantly comprising the cost of their use at industrial scale. It is also of particular interest for the industry that these new materials may also potentially provide advantages in properties such as hydrogen embrittlement resistance, so that they can be incorporated into hydrogen storage solutions.
Inventors:
Fernado Santos (AZTERLAN), Andrea Niklas (AZTERLAN), David García (AZTERLAN), Mikel Rouco (AZTERLAN), Teresa Guraya (EHU), Yoana Bilbao (EHU)
Keywords:
Steel, high entropy alloys, hydrogen.