[r9etb]

Somehow by random chance alloyed into 5mm spheres?

That's no big deal. After all, they make (or made) ball bearings by dropping molten metal off a tall tower. The plane dropped for a much longer time, giving plenty of time for a "metal fog" to form droplets that solidified as spheres.

There's still the problem of how such a fog might form, but that, too, might be explained away. Titanium has very high melting/boiling point (3034/5948 degF), but if it came into contact with burning aluminum (~5700 degF).

The missing link would be an ignition source for the aluminum, though it's possible that a high-voltage electrical spark onto a jagged edge might provide the necessary heat.

[JohnFiorentino]

What do we know about the spheres?......We know their size, we know where they were recovered, and we know their elemental composition. We also know, at least according to BOEING that they didn't come from the airplane.

The FBI report categorizes them as of "unknown origin"

Beyond that, we are left to speculate.

[eno_]

I do not think there was any evidence in the wreckage of an aluminum fire. It is possible but it happens most often as a result of fire started by munitions, on ships hit by missiles, for example. And even then, the odds of that fire involving, say, a Breitling wristwatch or a Callaway titanium golf club seems on the far side of unlikely. Too bad the article provides such a lousy description of the artifacts.