These are samples of the recently famous liquid metal: extremely tough, almost zero thermal expansion, low melting point. It can't be used in conjuction with other metals where there are temperature changes because it will tear the machine apart simply by not expanding along with the other metals.
According to Stalcup, "More than that, we have information that shows that 20 unusual .2-inch-diameter round pellets that were found in bodies were withheld from the NTSB but analyzed by the FBI and found to have been made of aluminum titanium matrix and other elements like zirconium, barium and cerium. These are pyrotechnics or incendiary devices, and the matrix structure of these objects is consistent with pellets used in antiaircraft missiles."
The FIRO chairman continues: "In fact, I found a quote in National Defense magazine that was referring to warheads that said 'pellets imbedded in titanium matrix' are used in antiaircraft warheads. The 'secret' [Brookhaven] report analysis concluded that the origin of the pellets is 'unknown' and that one of the pellets was submitted for identification because of its dissimilarity in appearance with TWA 800 debris. ...'"
The Brookhaven report on the pellets was just posted
http://www.twa800.com/pdf/brookhaven-report.pdf