Fabrication of metal matrix composite containing manganese nitride showing giant negative thermal expansion by compressive torsion processing

Antiperovskite manganese nitride Mn_3.1Zn_0.5Sn_0.4N was composited with Al by compressive torsion processing (CTP). This class of nitrides is anticipated for use as a thermal-expansion compensator because of giant negative thermal expansion (NTE). It is difficult to form a composite with molten metal that causes a chemical reaction. To date, only limited success has been achieved. Composites formed by CTP at 573 K exhibit lower thermal expansion and electrical resistivity than those produced by electric-current sintering. That achievement is attributable to suppressed chemical erosion of the filler by treatment at a lower temperature while the strong mechanical energy strengthens the interface between the filler and the matrix and reduces pores in the material. Compressive torsion processing is a promising method for forming metal matrix composites containing giant NTE fillers. (author)