Metallurgy

Tungsten has high tensile strength and good creep resistance. At temperatures above 2205 OC (4000 OF), tungsten has twice the tensile strength of the strongest tantalum alloys and is only 10% denser. However, its high density, poor low-temperature ductility, and strong reactivity in air limit its usefulness. Maximum service temperatures for tungsten range from 1925 to 2480 "C (3500 to 4500 OF), but surface protection is required for use in air at these temperatures.

Wrought tungsten (as cold worked) has high strength, directional mechanical properties, and some room-temperature toughness. However, re crystallization occurs rapidly above 1370 "C (2500 OF) and produces a grain structure that is crack sensitive at all temperatures.

Martensite crystals ideally have planar interfaces with the parent austenite. The preferred crystal planes of the austenite on which the martensite crystals form are designated habit planes, which vary according to alloy composition. In steels, the parent phase is usually austenite with a face-centered cubic (fcc) crystal structure, but the crystal structure of the product phase may be body-centered cubic (bcc). Under special conditions, steels undergo martensitic transformations in which the crystal structure of the product phase reverts to that of the parent. Most medium-carbon and high-carbon steels form martensite with a bct crystal structure, because carbon atoms occupy only one of the three possible sets of octahedral interstitial positions.

Allotropy means the property by which certain elements (like Fe) may exist in more than one crystal structure. Iron exists in two allotropic forms: BCC and FCC. In other words at 700°C (1290°F) it undergoes an allotropic transformation from FCC to BCC (in quenching, i.e. iron has FCC structure above this temperature and BCC structure below that).

The word ceramic is derived from the Greek word keramikos, "having to do with pottery". The term covers inorganic non-metallic materials whose formation is due to the action of heat. Up until the 1950s or so, the most important of these were the traditional clays, made into pottery, bricks, tiles and the like, along with cements and glass.

Historically, ceramic products have been hard, porous, and brittle. Technical Ceramics can also be classified into three distinct material categories:

Oxides: Alumina, zirconia

Non-oxides: Carbides, borides, nitrides, silicides

Composites: Particulate reinforced combinations of oxides and non-oxides.

Ceramic materials can be crystalline or amorphous. They tend to fracture before any plastic deformation takes place, which results in poor toughness in these materials. Additionally, because these materials tend to be porous, the pores and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the tensile strength. These combine to give catastrophic failures, as opposed to the normally much more gentle failure modes of metals.

Due to the consumption of a large amount of fossil energies to purify, ferrous alloys are not environmental. USA has stopped most of its steel mills, and the strategy is to concentrate mills in the developing countries. In non-ferrous alloys, let us consider only the mostly used alloys, which are copper alloys (including copper, brass, and bronze) and aluminum alloys. Because the rest are produced so much less than mentioned alloys that they are not actually a threat to the environment, furthermore, they are mostly extracted during refining Fe, Al, and Cu. Production of Cu and AL involves melting and electrolyzes procedures. However, the energy per kilogram pure Al needs is much higher than even Fe, but the most of the energy is electrical and much cleaner than that used for Fe. For Cu, through pirometallurgy methods a large amount of energy is gained autogenously, i.e. exothermal reactions occurred during copper making process supply a large amount of energy needed, but it involves producing products that are not environment. There are hydrometallurgy methods to produce copper, which are more environment-friendly.

In physics, thermal conductivity, (showed by the Latin capital of land), is the intensive property of a material which relates its ability to conduct heat.

Thermal conductivity is the quantity of heat, Q, transmitted through a thickness L, in a direction normal to a surface of area A, due to a temperature gradient (delta T), under steady state conditions and when the heat transfer is dependent only on the temperature gradient.

In general, thermal conductivity tracks electrical conductivity metals being good thermal conductors. There are exceptions: the most outstanding is that of diamond, which has a high thermal conductivity, between 1000, and 2600 W/mk, while its electrical conductivity is low.

I have been thinking about this overnight but I am not a chemist so I am unsure of the reactions. I do know that the penny gets shiny when you remove oxygen and impurities like sulfur from the surface. So lets reason together on this....The salt breaks down into hydrogen and chlorine in the water and produces a slightly acidic, HCl, solution. This breaks down the copper oxide pretty well. I do know the chlorine works well to clean of the copper oxide, I use "comet cleaner" with chlorine to clean brass. Now the vinegar has an acetic acid, but this is carbon, hydrogen and oxygen and I think that the salt combines with this to form a slightly basic solution and generates CO2. I would be interested in seeing if the vinegar salt solution with water added would improve the cleaning capability.

The calculation is so easy if you have the iron-carbon diagram in your mind. Proeutectoid ferrite is ferrite formed before eutectoid transformation. At 0.8 wt% carbon, we got 100% austenite before the transformation and at 0.02wt% carbon, we got 100% ferrite, and between these two values of carbon content, we have different amounts of proeutectoid ferrite.

Considering that, we have x wt% carbon we calculate proeutectoid ferrite using the tie line.

Proeutectoid ferrite amount = (0.8-x)/ (0.8-0.02)*100=45

==> x=0.45 wt%

You can check it with eyes. At the middle of the tie line, we must have 50% austenite, 50% ferrite; and it is at (0.8-0.02)/2=0.38%C.

We have 45% ferrite, which is less than 50% so we are closer to eutectoid point (0.8%C); so the carbon content must be more than 0.38%.