Mfr. of locally reinforced aluminium alloy composite material - by mixing silicon carbide whiskers with alloy powder, sintering then partially coating with thin aluminium film etc.

摘要

Al alloy composite material is produced by mixing SiC whiskers (10-50 microns dia. 0.1-5 microns and length 30-100 microns) and Al alloy powder and sintering to give a starting material. This is then partially coated with a thin Al film (min. purity 99%) some 0.5-20 microns thick by preheating the material to 20-100 deg.C below the solidus temp., then heating the matrix Al alloy 50 deg.C above its liquidus temp. Prod. is then placed in a mould and cast at a pressure of 250-3000 kg/cm2. USE/ADVANTAGE - For the internal combustion engine items, e.g. pistons, avoids problems associated with othr reinforcing systems, e.g. Al2O3 surface films gives good bond strength between matrix material and reinforcer. In an example, Al alloy powder (250 mesh size or less) was dispersed in water along with SiC whiskers (0.5 microns dia. and average length 20 microns), then filtered and dried to give a whisker content of 15%. This was heated to 600 deg.C and 5 x 10 power (-5) torr vacuum and sintered at a pressure of 100 kg/cm2 and press time of 20 minutes to give a slide shape starting piece of 50mm thickness and 80 mm dia. Slide was cut in half to give a semi-circle and Al foil (99% pure and 1 microns thick was applied to its surface in vacuo. This was then preheated in Ar at 500 deg.C, and the molten matrix material (Al alloy AC8A, same as starting powder) at 700 deg.C was poured in and pressure cast at 500 kg/cm2. A test piece of the part reinforced item showed a good tensile strength (35 Kgf/mm2).