Grain refinement of W-Ni-Fe heavy alloys by tantalum element adding①
(1. Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China;
2.State Key Laboratory for Powder Metallurgy,
Central South University, Changsha 410083, China)
2.State Key Laboratory for Powder Metallurgy,
Central South University, Changsha 410083, China)
Abstract: 90W-7Ni-3Fe and (90-x)W-xTa-7Ni-3Fe (x=1,3,5,7,10) specimens were attained by liquid phase sintering. A model describing the process of liquid forming and spreading was proposed to point out the differences between alloys doped with tantalum and traditional tungsten heavy alloys. Tantalum priority of entering matrix and a relative high solubility in liquid matrix depress tungsten solubility in liquid matrix, which decreases kinetic rate constantKand conse-
quently results in the reduction of W grain size. The grain refinement is influenced by Ta content and becomes more obvious when Ta content is over 5%. The sample with less than 3%Ta has dominant W and matrix phases. While besides W and matrix phases, intermetallic phases emerge in 85W-5Tai-7Ni-3Fe sample. Ta is superfluous and forms a new tantalum phase when more than 7% Ta is added into alloys.
quently results in the reduction of W grain size. The grain refinement is influenced by Ta content and becomes more obvious when Ta content is over 5%. The sample with less than 3%Ta has dominant W and matrix phases. While besides W and matrix phases, intermetallic phases emerge in 85W-5Tai-7Ni-3Fe sample. Ta is superfluous and forms a new tantalum phase when more than 7% Ta is added into alloys.
Key words: tungsten heavy alloys; alloying element addition; grain refinement; tantalum