チタンおよびチタン合金における双晶形成とAcoustic Emission

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  • チタン オヨビ チタン ゴウキン ニ オケル ソウショウ ケイセイ ト Aco
  • Acoustic Emission Accompanied by Twin Formation in Titanium and Titanium Alloy

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Abstract

チタンおよびチタン合金の圧延板について,単軸引張試験を行なった。試料はJIS2種純チタンとTi-6A1-4Vの圧延板で,引張試験時のAcoustic Emission(AE)を測定し,AEと機械的性質の異方性,特に双晶形成の状態との対応を調べた.主な結果は次のごとくであった。(1)結晶粒度の小さな純チタンでは,AEの発生がほとんどないことから双晶は形成されず,すべりだけで変形する。(2)粒度の大きい場合は双晶が形成され,それに対応したAEが観察される。また,異方性への双晶の寄与の程度もAEの発生挙動から推定できる。(3)Ti-6A1-4Vでも双晶に対応するAEの発生がある。(4)擬単結晶モデルを適用して,方位因子による双晶系の解析を行なった結果,AEから予想される双晶形成頻度と方位因子の大小との間に一致がみられたが,双晶系の是非に関する確認はできなかった。

Acoustic emission was measured during tensile test of titanium and Ti-6A1-4V alloy rolled sheets. The purpose of this paper is to investigate the relationship between acoustic emission and the deformation twinning which is considered to play an important role in the mechanical anisotropy in titanium. The results obtained are as follows: (1) In the case of titanium of small grain size, only very low-amplitude acoustic emission pulses were observed. From this result, it is considered that twinning does not occur in this condition and the material deforms only by slip. (2) In the case of titanium of large grain size, a number of large burst of pulses was observed, which is thought to correspond to the twin formation. Moreover, from acoustic emission characteristics, we could estimate the contribution of twins to the mechanical anisotropy of titanium. (3) In Ti-6A1-4V alloy, acoustic emission pulses were observed in correspondence with twin formation. (4) It was found that the amount of twin formation increased with increase in the Schmid factor calculated on the assumption of a so-called quasi-single crystal model, but the twinning mode was not confirmed.

資料番号: SA0124498000

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