Nickel / titanium alloy having a surface substantially free of nickel and its manufacturing method

摘要

PROBLEM TO BE SOLVED: To provide a Ni-Ti alloy having a surface layer containing substantially no Ni and having a low probability of causing troubles due to a Ni elution and a method of producing the same.SOLUTION: A method of producing a nickel-titanium alloy having a surface layer having a nickel atom density of 10% or less, or preferably 5% or less comprises a step of anodizing the nickel-titanium alloy in an aqueous solution of 0.03-0.3 M, preferably 0.05-0.1 M, or more preferably 0.1 M nitric acid or a nitrate salt. The nickel-titanium alloy has a surface layer having a nickel atom density of 10% or less at positions from its surface to a depth of at least 50 nm from the surface, and a surface having an arithmetical average roughness of 8 nm or less.EFFECT: By surface treatment by the method, a Ni-Ti alloy having a surface layer containing substantially no Ni and having a low probability of causing troubles due to a Ni elution can be produced. The Ni-Ti alloy can be a metal material that is safer for human bodies and also maintains superelasticity.SELECTED DRAWING: Figure 2