Editing Magnetostriction (section)

====Effect of microstructure on elastic strain alloys==== 
[[Single crystal|Single-crystal]] alloys exhibit superior microstrain, but are vulnerable to yielding due to the anisotropic mechanical properties of most metals. It has been observed that for [[polycrystalline]] alloys with a high area coverage of preferential grains for microstrain, the mechanical properties ([[ductility]]) of magnetostrictive alloys can be significantly improved. Targeted metallurgical processing steps promote [[abnormal grain growth]] of {011} grains in [[galfenol]] and [[alperm|alfenol]] thin sheets, which contain two easy axes for magnetic domain alignment during magnetostriction. This can be accomplished by adding particles such as [[boride]] species <ref>{{cite journal|last1=Li|first1=J.H.|last2=Gao|first2=X.X.|last3=Xie|first3=J.X.|last4=Yuan|first4=C.|last5=Zhu|first5=J.|last6=Yu|first6=R.B.|date=July 2012|title=Recrystallization behavior and magnetostriction under pre-compressive stress of Fe–Ga–B sheets|journal=Intermetallics|volume=26|pages=66–71|doi= 10.1016/j.intermet.2012.02.019}}</ref> and [[niobium]] carbide ({{chem2|NbC}}) <ref>{{cite journal|last1=Na|first1=S-M.|last2=Flatau|first2=A.B.|author2-link=Alison Flatau|date=May 2014|title=Texture evolution and probability distribution of Goss orientation in magnetostrictive Fe–Ga alloy sheets|journal=Journal of Materials Science|volume=49|issue=22|pages=7697–7706|doi= 10.1007/s10853-014-8478-7|bibcode=2014JMatS..49.7697N|s2cid=136709323}}</ref> during initial chill casting of the [[ingot]].

For a polycrystalline alloy, an established formula for the magnetostriction, λ, from known directional microstrain measurements is:<ref>{{cite journal|last1=Grössinger|first1=R.|last2=Turtelli|first2=R. Sato|last3=Mahmood|first3=N.|date=2014|title=Materials with high magnetostriction|journal=IOP Conference Series: Materials Science and Engineering|volume=60|issue=1|pages=012002|doi= 10.1088/1757-899X/60/1/012002|bibcode=2014MS&E...60a2002G|doi-access=free}}</ref>

λ<sub>s</sub> = 1/5(2λ<sub>100</sub>+3λ<sub>111</sub>)

[[File:Tensiletestgallium.png|thumb|Magnetostrictive alloy deformed to fracture]]

During subsequent [[hot rolling]] and [[Recrystallization (metallurgy)|recrystallization]] steps, particle strengthening occurs in which the particles introduce a “pinning” force at [[grain boundaries]] that hinders normal ([[stochastic]]) grain growth in an annealing step assisted by a {{chem2|H2S|link=hydrogen sulfide}} atmosphere. Thus, single-crystal-like texture (~90% {011} grain coverage) is attainable, reducing the interference with [[magnetic domain]] alignment and increasing microstrain attainable for polycrystalline alloys as measured by semiconducting [[strain gauges]].<ref>{{cite journal|last1=Na|first1=S-M.|last2=Flatau|first2=A.B.|author2-link=Alison Flatau|date=May 2014|title=Texture evolution and probability distribution of Goss orientation in magnetostrictive Fe–Ga alloy sheets|journal=Journal of Materials Science|volume=49|issue=22|pages=7697–7706|doi= 10.1007/s10853-014-8478-7|bibcode=2014JMatS..49.7697N|s2cid=136709323}}</ref> These surface textures can be visualized using [[electron backscatter diffraction]] (EBSD) or related diffraction techniques.