| 摘要 |
PURPOSE:To provide high hardness to a Ti alloy without deteriorating ductility, by subjecting a Near-beta-type Ti alloy in which Mo equivalent value is specified to solution heat treatment and then to working under respectively limited conditions and by applying two-stage ageing treatment to the above. CONSTITUTION:A Near-beta-type Ti alloy in which the value of Mo equivalent represented by an expression is regulated to 5-14 is subjected to solution heat treatment consisting of holding at a temp. in the region between (beta-transformation point-150 deg.C) and (beta-transformation point+300 deg.C) for 0.01-2hr and cooling at >=1 deg.C/sec cooling rate. Subsequently, working, such as forging and hot rolling, is applied at a temp. in the region from room temp. to 200 deg.C at 5-50% draft. After the working treatment, the alloy is subjected to primary ageing treatment consisting of holding at 250-400 deg.C for >=8hr, and successively to secondary ageing treatment consisting of holding at 500-600 deg.C for 0.5-2hr. By the above heat treatments, high hardness can be provided to the Ti alloy without deteriorating ductility.
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