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Proposed new strategy to construct pure bulk tungsten

A kind of high performance bulk pure tungsten with high strength and excellent low temperature ductility, was recently fabricated by a collaborative research team of Institute of Solid State Physics, Hefei Institutes of Physical Sciences (HFIPS) , Chinese Academy of Sciences (CAS), and Xi’an Jiaotong University.

Related research was published in Acta Materialia.

Tungsten (W) and its alloys have attracted much attention with its good performance. But pure W has an intrinsic fragility and is subject to operational embrittlement by grain enlargement and neutron irradiation.

In this research, by sintering the W powders activated by a low-temperature sintering procedure, the scientists obtained a high-density bulk W slab with a particle size of 8.9 μm. Subsequent HERF hot work further refined the grains and built up the grains of the lamellar matrix, with abundant inner fine subgrains and a high density of moving edges and mixed dislocations. The shielding and blunting effects of low angle grain boundaries and highly mobile dislocations, as well as the hardening effect of delamination harvested by the lamellar structure are the main mechanisms for the ductility and strength enhancement at low temperature.

The performance of this fine-grained W was outstanding, according to the team.

At room temperature, its yield strength is 1302 MPa, exceeding other reported bulk tungsten materials. Obvious tensile ductility was detected, which was the first time tensile strain was achieved at room temperature for bulk tungsten products.

The researchers also tested its tensile performance at high temperatures. The ultimate tensile strength and total elongation at 600 ohC still maintained at a high level of 843 MPa and 10.2%, respectively. The resistances are much higher than those of previously reported bulk tungsten materials at the temperatures tested.

“The grain has been refined to around 1.3 μm,” said Xuebang Wu, who conducted the research, “which contributes to the brilliant low-temperature properties of this material.”

He further explained the structure of bulk tungsten. The synergistic effect of lamellar elongated grain structures, high proportion of low angle grain boundaries and highly mobile dislocations ensured improved low temperature ductility and strength.

“Prepared high-performance pure bulk W has good application prospects in fusion reactors and high-temperature industries,” Wu said, “and we believe this strategy is a feasible and low-cost route to designing high performance refractory metals and alloys”.

– This press release was originally posted on the website of the Hefei Institutes of Physical Sciences of the Chinese Academy of Sciences