Samples of pure tungsten and tungsten heavy alloy (WHA) pellets, with compositions of 91 percent tungsten-6 percent nickel-3 percent cobalt (91W-6Ni-3Co), and 97 percent tungsten-2 percent nickel-1 percent iron (97W-2Ni-lFe) were implanted in rats to assess the potential adverse effects of WHA fragments embedded in the body. The studies demonstrated that rats implanted with the 91W-6Ni-3Co composite developed metastatic tumors originating at the implant site. The rats implanted with pure W or the 97W-2Ni-lFe composite developed no overt adverse effects. In this paper, metallurgical characterizations were performed to examine the differences between the in-vivo corrosion and toxicity of the 97W-6Ni-3Co, 97W-2Ni-lFe, and pure W pellets implanted in the rats for 3, 6, and 12 months. These analyses may provide a microstructural correlation with toxicity and/or adverse health effects of the particular alloys of interest.
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