Fabrication processes high pressure melt forming

The alloys are first produced by rapid solidification and are amorphous in nature. They are either directly fabricated as powders, by a process such as high-pressure gas atomisation (HPGA), or by melt-spinning of ribbons, which are subsequently pulverised to form a powder (<150 /im). The powders are then consolidated by hot extrusion between 950-1050°C where the initial amorphous structure breaks down and forms a fine dispersion of stable borides in a ductile Fe-based matrix. 

Different polymer properties, that is the ability to form injection-moulded products, sheet, film, extruded products (tubes, fibres etc), all require different MWs. When the MW becomes greater than 10 then the polymer becomes difficult to process, since it will not melt and depolymerizes or decomposes when heated. These materials are fabricated by sintering (by applying pressure and heat). Examples include PTFE and ultra-high molecular weight PE (UHMWPE). 

Injection molding produces solid parts in large volumes at high production rates. It permits close tolerances and the manufacture of very small pieces which are difficult to fabricate in quantity by other methods. Scrap losses are minimal compared to other forming methods because it is one of the only commercial processes where scrap can be reground and remolded at the machine. Melt material is injected into the mold from an extrusion barrel where it is maintained under pressure (Figure 1.6). When the pan has sufficiently solidified, the mold qiens and the part is ejected. 

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