The special properties of nickel and titanium alloy

1, the characteristics of shape memory (shape memory) shape memory is when the mother of a certain shape by Af temperature cooled to Mf temperature above the following after the formation of martensite, the martensite temperature deformation under Mf, and through heat below Af temperature, along with the inverse transformation, material will automatically restore its shape in the parent phase.Actually shape memory effect is one of the nickel titanium alloy by thermal induced phase transformation process. titaniumcn
2, super elasticity (superelastic) of hyperelastic refers to the sample production under external force is greater than the elastic limit stress strain variable, the phenomena of strain can be automatically restored when unload.Namely in the parent phase state, as a result of the action of applied stress, cause stress induced martensite phase transformation, thus alloy showed different from ordinary material mechanics behavior, its elastic limit is far greater than ordinary materials, and no longer comply with hooke's law.Compared with shape memory properties, hyperelastic without heat.To sum up, super elasticity refers to the internal stress within a certain deformation range increase along with the increase of strain, super elasticity can be divided into two categories, linear superelasticity and nonlinear hyperelastic.The stress-strain curve of stress and strain of the nearly linear relationship.Nonlinear hyperelastic refers to the Af above a certain temperature range, respectively, in the process of loading and unloading stress induced martensitic transformation and its inverse transformation results, so the nonlinear hyperelastic also called phase change pseudo elastic.Phase change of the nickel titanium alloy pseudo elastic can reach about 8%.Nickel titanium alloy of hyperelastic can change with the change of the heat treatment conditions, when the arch wire is heated to 400 & ordm;C above hyperelastic began to decline.
3, in the mouth temperature sensitivity: stainless steel wire and treatments of the CoCr alloy wire tooth orthopaedic basic is not affected by the influence of the temperature of the mouth.Treatments of the superelastic Nitinol wire tooth orthopaedic force along with the change of oral temperature changes.When the deformation must be.And correcting force increases as the temperature increases.On the one hand, it can accelerate the movement of the teeth, this is because the change of temperature in the oral cavity can cause capillary stimulation caused by rectification device stagnation of blood flow, blood flow to the sluggish rate so as to make the repair cells in the process of moving teeth get adequate nutrition, to maintain its vitality and normal function.Orthodontic doctors can't accurate control, on the other hand, or force measurement of oral environment correction.
4, corrosion resistance, studies have shown that the corrosion resistant properties of nickel and titanium wire and stainless steel wire
5, poison resistance: niti shape memory alloy special chemical composition, that is, this is a nickel titanium alloy atom, containing about 50% of the nickel, nickel and known have carcinogenic effect and promote cancer.General cases, the surface layer of titanium oxide ACTS as a barrier, the Ni Ti alloy has good biocompatibility.Surface layer TiXOy and TixNiOy can inhibit the release of the Ni.
6, treatments of the soft power: the teeth of commercial application of wire including austenitic stainless steel wire, cobalt - chrome - nickel alloy wire, nickel chromium alloy wire, alloy silk, gold wire and Australia to decide the titanium alloy wire.About the orthodontic correction of wire in the tensile test and three point bending test conditions of load - displacement curve.Nickel titanium alloy curve of unloading platform the lowest and most flat, it can provide most persistent treatments of the soft power.
7, good damping characteristics: caused by chewing and night molars for arch wire vibration, the greater the damage of tooth root and periodontal tissue.Through different attenuation experiment results, the study found the arch wire stainless steel wire vibration amplitude is larger than hyperelastic nickel titanium silk, super elastic nickel-titanium arch wire the initial vibration amplitude is only half of stainless steel wire, good vibration and shock absorption characteristics of the arch wire is important for the health of the teeth, and traditional arch wire such as stainless steel wire, tend to increase the root absorption.