Combined soft magnetism, good corrosion resistance, and high mechanical strength in glassy Fe65.5Cr4Mo4Ga4P12C5B5.5

Amorphous alloys are good candidates for application as soft magnetic materials because of the lack of crystal anisotropy. Amorphous materials with enhanced glass formability give an opportunity to improve the value in use of amorphous materials further. Conventional soft magnetic alloys often have very high mechanical strength and high resistance against corrosion which may be important for application as magnetic parts in valves, clutches, or relays. In this paper, Fe_65.5Cr₄Mo₄Ga₄P₁₂C₅B_5.5 bulk metallic glass (BMG) was cast to various shapes: discs (10 mm diameter, 1 mm thickness), cylindrical rods (1.5-3 mm diameter), and bars with rectangular cross-section (2 mm × 2 mm). Structural characterization was done using X-ray diffraction (XRD) and the thermal transformation behavior was studied by differential scanning calorimetry (DSC). The magnetic properties were measured by means of a Forster-coerzimat (H_c), a B-H loop tracer (low field behavior) and a vibrating sample magnetometer. Magnetostriction was determined by the strain gauge method. Annealing was done between 350°C and 450°C. Good soft magnetic behavior was documented by low coercivities in the range 3-9 A/m for the amorphous samples and 62 A/m for the rod with 3 mm diameter. Corrosion resistance of the BMG was compared with 430F stainless steel using electrochemical test. This test showed that the bulk amorphous samples have a much lower corrosion current density in acid media than the ferritic stainless steel. Mechanical compression tests of the BMGs were also performed. Based from the results, casting to a thicker rod and annealing of the samples enhanced the Young´s modulus E and reduce the elastic range ε_e.