thanks for the answer before But im still dont get understan

thanks for the answer before. But im still dont get understand, what actually was the magnetic characteristic after forming martensite,how the mechanism of non- magnetic turn become magnetic ? what is magnetic actually mean?
then, heat treatment (@400C & @800C) conduct to the speciments,what should be happen correctly?

Solution

Formation of Martensite:-

Rapid cooling is very necessary to form Martensite.

In Carbon steels Martensites will forms by the rapid cooling of the austenite form of Iron at a high rate that carbon are atoms do not have time to diffuse out of the crystal structure in large enough quantities to form cementite.

Martensite:-

Martensite is not given away in the equilibrium phase diagram of the iron-carbon system. Martensite is not an equilibrium phase.

Generally equilibrium phases are forming by the slow cooling rates that allow the satisfactory time for distribution at this stage martensite is usually formed by very high cooling rates.

Temering:-

Since chemical processes accelerate at higher temperature and then martensite is easily destroyed by the heat. This process is called “tempering”.

Rapid Cooling (Qenching):-

Martensite is formed in carbon steels by the rapid cooling of austenite form of iron at such a high rate that carbon atoms do not have time to diffuse out of the crystal structure in large enough quantities to form cementite.

Difference to the austenitic alloys ferritic stainless steels such as 409 or 3Cr12/5Cr12 and the martensitic stainless steels such as 420 are powerfully attracted to a magnet still in the annealed state.

As end result, the face-centered cubic austenite transforms to a highly strained body-centered tetragonal form called martensite that is supersaturated with carbon. The shear deformations that result manufacture large numbers of dislocations, which is a primary strengthening mechanism of steels.

The maximum hardness of a pearlitic steel is 400 Brinell whereas martensite can achieve 700 Brinell.

Generally, martensitic reaction begins for the period of cooling when the austenite reaches the martensite start temperature and the parent austenite becomes mechanically unstable. As the sample is quenched, an more and more large percentage of the austenite transforms to martensite pending the lower transformation temperature M_f is reached, at which time the transformation is completed.

Magnetic:-

A magnet is an objective made of definite materials which generate a magnetic field. Every magnet has at least one north pole and one south pole.

A magnet contains electrons that have mutually uneven orbits and uneven spins. Individuals magnetic atoms are aligned in nice straight rows inside each domain and those domains are also lined up all in the same direction.

A magnet can attracts the ferrous objects like Iron, Nickel, Cobalt and the Steel pieces.

Magnetic Field:-

The space around the magnet, in which area the magnetic force produce, this is called as “Magnetic Field”.

Heat Treatment at 400C, 800C:-