Effect Of Directional Recrystallization Process On Microstructure And Properties Of Alloys

The microstructure of the material is an important factor in determining the material properties: a larger grain size can improve the high temperature mechanical properties of the material,and the alloy with a microstructure parallel to the grain boundary in the direction of tensile stress usually has excellent creep resistance and high fatigue resistance.Tightly aligned directional microstructure helps to inhibit crack propagation and increases the strength and toughness of the material.The columnar crystal CuAlMn alloy exhibits better ductility,shape memory effect and damping performance than the polycrystalline CuAlMn alloy.The same columnar nickel-base alloy also shows better high temperature creep and fatigue resistance.There are many factors affecting directional recrystallization,such as hot zone temperature,drawing rate,texture,etc.,in which the influence of process parameters on the microstructure can not be ignored.Therefore,understandingthe directional recrystallization process parameters is of great significance for both nickel-based alloy and the microstructure and mechanical properties of CuAlMn,and it becomes the focus of this paper.This paper investigated the effects of directed recrystallization on the microstructure and texture.It is found that the hot zone temperature must be above the secondary recrystallization temperature in order to obtain columnar crystals whether in nickel-based alloys or in CuAlMn shape memory alloys,and the columnar crystal growth is formed by the migration and growth of the front grain boundary..Nickel-based alloys can be oriented recrystallized at 1000 °C and 30 ?m/s to obtain columnar crystals with an aspect ratio of 3.The CuAlMn shape memory alloy is oriented at 900 °C and 15 ?m/s.Recrystallization can obtain columnar crystals with a longer aspect ratio.CuAlMn shape memory alloy has three kinds of textures containing {001}<110>,{223}<110> and {011}<110> at 800 °C.Sharp sharpening of the {223}<110> texture occurs at 850 °C.When the temperature rises to 900 °C,the texture continues to deflect,and only {332}<113> texture is typical.CuAlMn shape memory alloy has three textures of {223}<110>,{115}<110> and {111}<110> at a temperature of 900 °C in hot zone.{223} <110> texture has the highest strength at 10 ?m/s.At 20 ?m/s,the texture is deflected and the {115}<110> texture is prominent.When the speed continues to increase to 30 ?m/s,the texture strength is weakened.It is indicated that as the directional recrystallization process changes,the most typical texture orientation is also constantly deflected.By investigating the effects of oriented recrystallization process on the tensile properties and superelasticity: CuAlMn shape memory alloy has a peak value in the hot zone temperature of 900 °C yield strength and tensile strength as the extraction rate increases first and then decreases.Among them,the 900°C 20?m/s CuAlMn shape memory alloy has good tensile strength of 644 MPa,yield strength of 443 MPa,and superelastic strain of 2.2%.The CuAlMn shape memory alloy is recrystallized to 900 °C.The 15?m/s CuAlMn shape memory alloy has good superelasticity.The maximum superelastic strain energy is 4%,the tensile strength is 563 MPa,and the yield strength is 370 MPa,indicating that the strength rise will cause superelasticity to drop.By investigating the effect of microstructure on damping properties,the damping properties of CuAlMn shape memory alloys are not affected by the grain morphology at temperature,while CuAlMn shape memory alloys with columnar crystals at strain amplitude are at the same strain amplitude.The damping performance is better than that of CuAlMn shape memory alloys with equiaxed grains.And at different frequencies,as the frequency increases,the CuAlMn shape memory alloy with columnar crystals should first improve the damping performance faster than the CuAlMn shape memory alloy with equiaxed grains.