High Level Of Mechanical Properties Research Articles

Thermal oxidative stabilization of polyacrylonitrile precursor fiber—progression of morphological structure and mechanical properties

The progression of morphological structure and mechanical properties of PAN precursor fiber when treated under two drawing experiments on continuous stabilization stage has been characterized. Three steps are shown in the morphological rearrangements. An increase in lateral order and orientational order is observed in the initial stage, prior to the onset of significant chemical reactions in the material. Then the morphological order shows a rapid decrease with the occurrence of stabilization reactions, and following a slow change in measurements. The extent of morphological changes is found to depend on draw ratio imposed during stabilization. Experimental results indicate the presence of a less ordered phase, other than a lateral order phase in the material. The initial modulus and elongation at break go through three steps, corresponding to those of morphological order changes respectively. The tensile strength shows a continual decrease throughout the stabilization stage. Taking the two parallel experiments into comparison, it can be found that with some elongation made by stretching on stabilization, a higher level of mechanical properties is retained through the stabilization stage. The effect of stretching during stabilization on ultimate carbon fiber properties is surveyed.

Features of formation of the structure in production of blanks of disks of heat-resistant nickel alloys

To provide a high level of mechanical properties in wrought blanks of cast EP741NP and EP962 alloys it is necessary to form controlled structures. A “necklace”-type structure formed in homogenizing isostatic treatment, subsequent thermomechanical working including alternation of the operations of deformation in the (γ+γ′)-area and recrystallization anneals, and final heat treatment is preferable. The temperature conditions of all stages of thermomechanical working are strictly controlled, especially the final operation of deformation and heating for hardening. To eliminate hardening cracks and distortions it is necessary to use molten salts at t=600°C as quenchants. The use of multiple production operations makes it possible to significantly reduce the structural inhomogeneity related to inhertance of the original dendritic structure. However, the structure of the final semifinished product is nevertheless characterized by a difference in occurrence of the processes of polygonization and recrystallization between the former dendritic cells and the interdendritic spaces in deformation and heat treatment. To obtain structurally homogeneous blanks for gas turbine engine parts it is necessary to use basically new methods of remelting such as vacuum double electrode remelting and electron beam remelting with an intermediate vessel.

Substructural features of hardened low-alloy steel with boron

1. Hardening without tempering of low-alloy, low-carbon steel with microadditions of boron may provide a satisfactory combination of strength, ductility, and impact strength. 2. The high level of mechanical properties of the test steel with the strengthening treatment used was achieved with presence in its structure as the main component of acicular ferrite with a high dislocation density within laths and with a high level of ferrite grain fragmentation.

Chemical resistance of glass-filled polypropylene in the aggressive media of viscose manufacturing

The introduction of fiberglass somewhat increases the swelling of polypropylene in acidic media, but due to the preservation of a high level of mechanical properties, it permits one to increase the operational lifetime of parts and to reduce warping.

Influence of heat treatment on the structure and properties of 9G28Yu9MVB steel

As the result of development of the processes of decomposition of the solid solution at 650–750°C a significant improvement in the machinability of 9G28Yu9MVB steel occurs. The most intense softening and embrittlement of the steel occurs at 700°C, which provides the maximum improvement in its machinability. To provide a high level of mechanical properties of 9G28Yu9MVB steel it must be waterhardened from 1000°C and aged, using the diagrams given of the change in mechanical properties for selection of the cycle.

Steels for gas and oil pipelines

FIELD: ferrous metallurgy. SUBSTANCE: invention provides alloyed steel for products operated at very low temperatures and exposed to action of corrosive media causing hydrogen-stress cracking. Steel is composed of, wt %: carbon 0.02-0.07, manganese 1.45-1.80, silicon 0.03-0.10, vanadium 0.10-0.12, aluminum 0.03-0.05, sulfur <= 0.010, phosphorus <= 0.012, nitrogen 0.003-0.005 (calcium + barium + magnesium) 0.07-0.10, iron - the balance. EFFECT: ensured high impact elasticity at very liquid temperatures (-70 C) with high level of mechanical properties and increased corrosion resistance against hydrogen-stress cracking in presence of corrosive media containing hydrogen sulfide. 2 tbl

Sheet moulding compounds

After extensive development sheet moulding compounds are now gaining wide acceptance in the reinforced plastics industry. Large volume usage is already here in a wide range of applications. The high level of mechanical properties coupled with the good surface finish enable both structural and decorative components to be produced