New strategy for Constructing Bulk Pure Tungsten

A collaborative research group at the Institute of Solid State Physics, Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS), and Xi’an Jiaotong University has recently developed bulk pure tungsten with high strength and ductility at low temperatures.

Tungsten (W) and its alloys have attracted a lot of attention for their good properties. However, pure tungsten is inherently brittle and prone to operational embrittlement due to grain coarsening and neutron irradiation.

In this study, by sintering the activated W powder through a low-temperature sintering procedure, the scientists obtained high-density bulk W plates with a grain size of 8.9 μm. Subsequent HERF thermal processing further refined the grains, constructing lamellar matrix grains with a large number of fine sub-grains inside, as well as a high density of mobile edges and mixed dislocations.

The shielding and passivation effects from low-angle grain boundaries and highly mobile dislocations, as well as the layered toughening effect harvested by the lamellar structure, are the main mechanisms for improving low-temperature ductility and strength.

According to the research team, the properties of this fine-grained, large-volume pure tungsten are outstanding. With a toughness of 1302 MPa at room temperature, it surpasses other reported bulk tungsten materials with significant tensile ductility, the first time tensile strain has been achieved for a bulk tungsten product at room temperature.

The researchers also tested its tensile properties at high temperatures. The ultimate tensile strength and total elongation at 600 degrees Celsius remained at high levels of 843 MPa and 10.2%, respectively. These strengths are much higher than those previously reported for bulk tungsten materials at the tested temperatures.

"The grains were refined to about 1.3 microns," said Xuebang Wu, one of the team's authors, "which contributes to the room-temperature toughness and high strength of this material."

He further explained the structure of the bulk pure tungsten. The synergy of the lamellar elongated grain structure, the high proportion of low-angle grain boundaries and highly mobile dislocations ensures its low-temperature ductility and increased strength.

"The high-performance bulk pure tungsten we have prepared have promising applications in fusion reactors and the high-temperature industry," said Xuebang Wu, "and we believe this production strategy is a viable and low-cost way to design high-performance refractory metals and alloys." The related research was published in the top metal materials journal - Acta Materialia, and this collaborated press release was originally published on the Hefei Institutes of Physical Science, Chinese Academy of Sciences website.

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