Pinghua Lin

Effects of Mn doping on structural and magnetic properties in NdFeB nanocomposites

Abstract The magnetic and structural properties of nanocomposite Nd 9 Fe 85− x Mn x B 6 ( x =0,0.5,1) have been investigated. It was found that the addition of manganese in the Nd 9 Fe 85 B 6 could promote crystallization and enhance the hard magnetic properties of the material. Thermomagnetic analysis (TMA) measurement indicated that the doping of Mn reduces the T c of the Nd 2 Fe 14 B phase and raises that of α-Fe phase in the system. From the radial distribution curves around Fe atoms of Extended X-ray absorption fine structure (EXAFS), it has been demonstrated that for both the as-spun Nd 9 Fe 85− x Mn x B 6 ( x =0,0.5,1) samples with lower x value and the annealed samples, the EXAFS curves appear to be similar to that of α-Fe.

Improvement of pitting corrosion resistance for Al-Cu alloy in sodium chloride solution through equal-channel angular pressing

Abstract Significant corrosion resistance improvement was achieved in solid-solution treated (T4) Al-Cu alloy after severe grain refinement through equal-channel angular pressing. The bulk ultrafine-grained Al-Cu alloy with grain sizes of 200-300 nm has higher pitting potential (elevated by about 34 mV, SCE) and lower corrosion current density (decreased by about 3.88 µA/cm 2 ) in polarization tests than the as-T4 alloy, and increased polarization resistance (increased by about 5.7 kΩ·cm 2 ) in electrochemical impendence spectrum tests, along with alleviated corrosion damage in immersion tests. Two factors responds to the improved corrosion resistance of the alloy: the first is the refinement of residual θ -phase (Al 2 Cu) particles leading to the lower micro-galvanic currents and reduced susceptibilities to pitting corrosion, the second is the mass of strain-induced crystalline defects providing more nucleation sites for the formation of more volume fractions of stable oxide film.