Crystallographic textures in rolled and annealed Fe-Ga and Fe-Al alloys
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7/1/04
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Crystallographic Textures in Rolled and Annealed Fe-Ga and Fe-Al Alloys N. SRISUKHUMBOWORNCHAI and S. GURUSWAMY The feasibility of obtaining [001] preferred texture in polycrystalline Fe85Ga15 and Fe85Al15 magnetostrictive alloys containing 1 mol pct NbC using a low-cost conventional thermomechanical processing approach is shown in this work. Thermomechanical processing conditions examined consisted of a sequence of hot rolling, two-stage warm rolling at 400 °C with intermediate anneal at 900 °C and texture anneal in the temperature range of 900 °C to 1300 °C for time periods up to 24 hours. Textures present prior to and after texture annealing were characterized using orientation imaging microscopy in a scanning electron microscope. In the case of Fe85Ga15 alloy with 1 mol pct NbC, the deformation-induced texture after a two-stage warm rolling consists of mixed {100}110 and {111}110 type partial textures. Texture annealing of the Fe85Ga15 alloy with 1 mol pct NbC at 1150 °C for 2 hours changes the texture to a predominant texture that is close to {001}100. On increasing the annealing time to 24 hours, the texture shifts toward {110}100. While texture anneal at both 1150 °C and 1300 °C produces a [001] or near-[001] preferred orientation along the rolling direction in the Fe85Ga15 alloy with 1 mol pct NbC, 1150 °C–24 hour treatment was found to provide the strongest [001] orientation among the conditions examined. Similar trends are observed for the case of Fe85Al15 alloy with 1 mol pct NbC.
I. INTRODUCTION
IN a recent work, polycrystalline Fe-Ga alloys containing Ga in the range of 15 to 27.5 at. pct have shown large lowfield Joule magnetostriction as high as 270 106.[1,2,3] Joule magnetostriction refers to the reversible changes in the linear dimensions of a ferromagnetic material on the application of a magnetic field. Ferromagnetic materials such as Fe-Ga alloys that exhibit large Joule magnetostriction at low fields are of immense interest for use as acoustic sensors and generators, linear motors, actuators, damping devices, torque sensors, positioning devices, speakers, and microphones.[4,5] Fe-Ga alloys have attractive combinations of high mechanical strength, good ductility, large magnetostriction at low saturation fields and high-imposed stress levels, and relatively low associated cost. The largest saturation magnetostriction values in the body-centered-cubic (bcc) crystals of these alloys are obtained along the 001 crystal directions. While [001] single crystals of these alloys can provide a large magnetostriction, growth of single crystals is an expensive process and the near room-temperature mechanical properties obtained would be much less than that obtained in a polycrystalline alloy. It is thus desirable to obtain [001] textured polycrystalline alloys using a low-cost processing approach. Two of the viable approaches used in this work are (1) directional solidification of the alloys and (2) thermomechanical processing involving deformation and recrystalliz
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