Metallurgy

Yes, it does. I am not an expert in these things, but I do know that the parameters of the extrusion process directly affect the crystalline matrix of the alloy, which in turn governs the physical characteristics of the alloy. As the differences can be quite significant, I would recommend checking with qualified references for pertinent details. I know that quenching and max temperatures are big issues. Good luck, sorry I could not be of greater assistance.

Hardened steel does not generally deteriorate over moderate periods, especially not as short as ten years, providing it have been protected from corrosion. Strong magnetic fields and electric fields generated through or around the steel can have an effect, but this is highly unlikely. If your bolt carrier has been kept protected and oiled it should be fine. I have a shotgun that was made in 1740 which has lost none of its hardness as well as steel swords dating back to the 1600's that are still hard and sharp. You should not have a problem.

Not all metals are heavy. Hydrogen is a metal, and is the lightest element known. Lithium, also a metal is the third lightest element there are many heavy elements that are not metals. If you "Google" the definition of "metal" you will note the properties that qualify a substance as a metal. Mass (weight) is not the important factor. Common metals are heavy because they have a dense electron structure.

You may find the melting range of some frequently used stainless steels below. Steel is an alloy and instead of a unique melting point, has a melting range, which is the range in which under equilibrium conditions, liquid, and solid phases coexist.

304: 1400-1450 (oC)

308: 1400-1420 (oC)

316: 1375-1400 (oC)

There is no physical distinction between these two grades of stainless steels since there are very similar compositionally. However, it might be possible to differentiate them rapidly by comparing their electrical resistance (measurable via an ohmmeter), indeed with some considerations in order to minimize the errors. I assume you already know that the most reliable method of telling them from each other would be to perform a chemical analysis of them using EDS and other spectroscopy methods.

There are literally thousands of different ceramic products. They have widely varying atomic structures and characteristics.

It is the ability of a metal to become hard (and inevitably brittle) under a given cooling rate. Therefore, the higher the hardenability of an alloy, the lower the cooling rate required to harden the metal. We have more heard about the hardenability in steels rather than other alloys. This is because in steels, there are different phases which can appear subject to the applied cooling rate below the critical temperature (the eutectoid temperature) as well as the alloying elements present in that grade of steel. Most of alloying elements in steel improve its hardenability by decreasing the critical cooling rate required to obtain the hardest possible phase i.e. martensite.

As far as I am concerned, copper is known as a good and cheap conductor of electricity. Although there are some other elements, such as silver, with higher conductivities copper is preferred due to its being rather cheap. Sometimes because of weight considerations, aluminum is also used even though it has a lower conductivity compared to copper.

A metallurgical microscope is an inverted scope with light sources designed for magnifying structures of metallographically prepared specimens. The magnification is no different from most normal upright scopes. Companies including Nikon and Olympus produce the scopes and you will be able to find a plethra of information about the scopes on their websites. I would also consider contacting their sales reps to ask specific technical questions about the scopes.

Aluminum, while it is incredible for some applications due to it being lightweight, is a very soft and weak metal. There really is not any way to get it any where near the hardness of steel. What people are doing for applications requiring lightweight, but strong materials is going with some new age alloys, mostly consisting of titanium and nickel.

Stress relieving of alloy steels (like 4130) has no temperature outlined in the spec of the material. However, it is common practice to stress relieve 4130 between 1050 and 1200 F. This is high enough to relieve the stress with out being hot enough that the material has an austenitic phase change, which occurs around 1350 F.

A centrifugal system would certainly separate the mercury assuming you could maintain a fluidized bed and that there were not large differences in the sizes of the particles in the slurry. Depending on the volume involved, a vibratory table might be better. There are many other methods, but I would need to know the relative size / volume / solid-liquid ratio information in order to make a useful recommendation. You need to take special precautions in any case to preclude the release of mercury into the environment. This is very east to do I can help you there as well if you care to divulge the nature of your processing circuit.

A microscope is a microscope for most purposes. First, make sure the light source on the scope is useful in seeing whatever it is you want to see. Certain items are seen well in certain lights. The second thing, as I am sure you have already realized, is that you will have a tough time determining where on the sample you are looking, as it is up side down. For this reason, I even prefer a non-inverted scope even for metallurgical tasks. In summary, if you are ok with the sample being upside down, and the light source is sufficient, there is no reason it will not work to the magnification that scope is specified.

Heat affected zone is measured regarding the microstructure changes in the weld. For example in steels, this is the area around the weld zone, which has undergone a transformation. In other words, this is the area, which had been austenitized. For calculating the HAZ after welding, for steels, it is better to macroetech the section of the weld HAZ can be easily recognized by the contrast it makes with the base metal and the weld metal.