Hypereutectoid alloys

Mass fractions of a proeutectoid phase (ferrite or cementite) and pearlite may be computed using the lever rule and a tie line that extends to the eutectoid composition (0.76 wt% C) [e.g., Equations 9.20 and 9.21 (for hypoeutectoid alloys) and Equations 9.22 and 9.23 (for hypereutectoid alloys)]. 

Interphase Precipitation in Hypereutectoid Fe-C-Cu Alloys , Acta Metall. Mat., 43(7), 2589-2604 (1995) (Phase Relations, Experimental, 46)... 

Schl] Schissler, J.-M., Metauer, G., Dilatometric Study of the Second Stage of the Isothermal Bai-nitic Transformation at 420°C of Hypereutectoid Fe-C-Si Alloys with 3.9% Siheon. Observation of a New Carbide (in French), Compt. Rend. Hebd. Acad. Sci., Ser. C, 277(21), 1081-1083 (1973) (Experimental, Crys. Stmcture, 6)... 

Iroii alloys with caibon content of less than 2% are known as steels and those with more than 2% are known as cast iron. Steels are further divided into those with carbon content of more than 0.8%, called hypereutectoid steels, and those with caihon content of less than 0.8%, known as hypoeutectoid steels. Most steels used in pressure vessel applications have a carbon content of less than 0.4%. Steels with carbon content of over 0.4% are very brittle and hard to weld. 

Figore 9.32 Schematic representations of the microstructures for an iron-carbon alloy of hypereutectoid composition Q (containing between 0.76 and 2.14 wt% C) as it is cooled from within the austenite-phase region to below the eutectoid temperature. 

Relative amounts of both pearlite and proeutectoid FcjC microconstituents may be computed for hypereutectoid steel alloys in a manner analogous to that for hypoeutectoid materials the appropriate tie line extends between 0.76 and 6.70... 

The material law of the near surface layer of the friction surfaces was described using the equations of the classical theory of plasticity, taking also into consideration the influence of the state faetors (temperature, strain rate, strain and stress state), which modify the plasticity and the deformability in a veiy wide range. Using unalloyed carbon steel and rapidly solidified, power metallurgy, hypereutectoidal aluminium alloy, the influence of the hydrostatic pressure on the plasticity and deformability was determined experimentally. 

On one hand, a ductile material, C45 unalloyed carbon steel was investigated. On the other hand, a rapidly solidified, power metallurgy, hypereutectoid aluminium alloy (AlSi26Ni6), which is practically not deformable at room temperature and atmospheric pressure. 

In the case of the hypereutectoid aluminium alloy, it is especially visible, that the dependence of the deformability on the Lode-parameter became negligible, even in the region of the higher hydrostatic pressure, there is no more difference between et /<<,= curves (see Figure 10). 

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