Mechanical properties of magnetic intermetallic materials

The purpose of this research is to (i) investigate the mechanical properties of the existing high-temperature soft and hard magnetic materials for such applications, and (ii) explore the composition technology for the improvement of the magnetic materials and their alloys. Fe-Co and Sm ₂ Co₁₇ alloy systems were chosen as the focus of the mechanical property study in this investigation.; The flexural strength and fracture toughness of Sm(Co, Fe, Cu, Zr) _7.4 was characterized as a function of temperature up to 600°C. The effects of orientation with respect to lamellar phase, thermal exposure at 450°C and the state of magnetization were studied. Under all conditions, the strength and toughness exhibit increasing or virtually stable trend with temperature up to 600°C. Magnetization leads to lower strength and toughness in the transverse direction where the broken pieces repelled one another. The longitudinal properties are largely insensitive to magnetization.; The high-temperature tension tests were done to determine the stress-strain curve and yield strength of Fe-Co soft magnetic materials. The effects of longrange order, temperature and grain size on the mechanical properties were investigated. The long-range order tends to decrease the yield strength of Fe-49-Co2V alloy. The yield strength is not sensitive to the strain rate within the temperature range of the anomalous behavior.; The electrodeposition method was used to manufacture the composites. Single fiber composites of both FeCo/W and FeNi/W material systems were manufactured. The FeNi/W composites exhibited very good consolidation, while the FeCo/W system showed poor matrix quality with plenty of voids. Further sintering at 1140°C could not eliminate the voids.; The theoretical analysis on soft magnet matrix composites was done to investigate the effect of improvement on creep. The analysis results show that with the reinforcing of tungsten wire, the longitudinal creep resistance of the composites system is much better than the monolithic soft magnetic phase itself. Due to the small aspect ratio of transverse cross direction, the effect of fiber reinforcement is not very promising.; The transverse thermal stresses were studied. FEM modeling results show that at 600°C, the whole matrix region reaches yielding at this temperature with the area along the interface yielding first at about 300°C. During the cooling stage, the circumferential stress becomes tensile along the interface. These results show that both radial and circumferential stresses may lead to crack at the interface.