Anisotropy of Mechanical Properties in Deformed Molybdenum Alloy Sheets

Abstract

When in a strain state, molybdenum alloy sheets exhibit distinct anisotropy of mechanical characteristics. The anisotropy of elastic, strength, and plastic characteristics is due to crystallographic and structural textures formed in the alloys in the course of rolling. The highest yield strength values, irrespective of the molybdenum alloy chemical composition, are noted in specimens cut transverse to the rolling direction. As to plasticity characteristics, no clear relationship is observed. For some alloys the maximum values of elongation are achieved in the specimens cut out in the rolling direction, while for the others an angle of 45°to the rolling direction. A tensorial criterion is put forward which allows description of the total curve of strength or elasticity characteristics in the plane of the sheet. The textural analysis has failed to give any positive results in describing the curve of yield-strength anisotropy but it can provide a fairly accurate description of the elastic modulus behavior.Strain anisotropy arises in molybdenum alloy sheets due to plastic deformation during forming (rolling) operations. The physico-mechanical characteristics governed by plastic deformation in the metal are not the same in various directions, i.e., they are anisotropic. This is attributable to a variation of the value of shear stresses that are active in variously oriented areas and responsible for an ambiguity of the extent of plastic deformation. In this case, the greatest distinction should be expected not between longitudinal and transverse (with respect to the rolling direction) stresses but between longitudinal and diagonal ones. Assessment of the degree of anisotropy in a material that experienced directional plastic deformation, e.g., in the process of rolling, from the standpoint of strength characteristics of specimens cut longitudinally in and transverse to the rolling direction is not only inadequate but also erroneous, for every so often significant differences in mechanical properties between intermediate directions are encountered.The present work addresses the in-plane anisotropy of mechanical characteristics of sheet molybdenum alloys whose chemical composition is given in Table 1 below.Sheets of the molybdenum alloys were made by multi-pass hot rolling at a temperature which was 100°C lower than the recrystallization temperature of these alloys. The final sheet thickness was 1.2 mm and the total strain upon rolling was 88%.Mechanical characteristics in uniaxial tension were measured on the specimens cut from a sheet at various angles to the rolling direction (RD). The specimens cut longitudinally (LD) and transverse to the rolling direction (TD) make respective angles 0°and 90°with the rolling direction. The cold-shortness temperature was assessed by the minimum temperature whereby all the specimens withstood 90°bending without breaking. 5660039-2316/05/3706-0566

Effects of annealing on the texture and anisotropy of unidirectional rolled Mo–La alloys

“…According to the changes of |Δr| and IPA values, the anisotropy of the Mo-La plate is gradually weakened from the rolled state to annealed state. The strength of the anisotropy is not entirely dependent on the texture, but also related to the grain size, grain shape and dislocations [29,30]. With the increase of annealing temperatures, the grain shape is changed from elongated fiber to uniform sphere and the dislocation density is also correspondingly decreased.…”

Effects of Molybdenum Microstructures on Sputtered Films

“…There- fore, the crystallographic orientations along the rolling and transverse directions are both softer ones in either textures. 21) When the reduction ratio is small, ©100ª normal direction has higher symmetry and might facilitate more slip systems to accommodate the rolling strains. On the other hand, for 85% rolled plate, the ©111ª normal direction has the lowest elastic moduli in molybdenum (292 GPa), and the orientations perpendicular to this direction all have elastic moduli of 308 GPa.…”