Fe-Mn-Si-Cr-N形状记忆合金中应力诱发马氏体量的测定

Measurement of the Volume Fraction of Stress-Induced Martensite in Fe-Mn-Si-Cr-N Shape Memory Alloy

通过 X射线衍射峰位置和强度的计算 ,可以测定 Fe- Mn- Si- Cr- N形状记忆合金中应力诱发马氏体 (ε相 )体积分数 .选择既不重叠又有足够强度的奥氏体的 {1 1 1 }γ、{2 0 0 }γ 和马氏体的{1 0 1 }ε衍射峰用于定量测定 γ相和 ε相的含量 ,并以定量金相结果进行了验证 .结果表明 ,该合金的应力诱发马氏体的体积分数 fhcp和应变量之间符合 Olsen和 Cohen用于 Fe- Cr- Ni合金的指数关系 :fhcp=1 - exp{- β[1 - exp(- αη) ]n},拟合的参数 α、β和 n分别为 1 2 .5、2 .2和 0 .5,其中 n值与Fe- Cr- Ni合金的 n值 (4.5)不同 ,表明 Fe- Mn- Si基合金在较小的应变量下就可获得比 Fe- Cr- Ni合金大得多的应力诱发马氏体量 ,原因可归结于两种合金的相变机制不同 .实验和拟合结果也证实了 Olsen和 Cohen认为的在 Ms点以上不能通过应力诱发得到 1 0 0 %的马氏体 .

The volume fraction of stress induced martensite (SIM) in Fe Mn Si Cr N shape memory alloy was determined by X ray diffraction method. The {111} γ and {200} γ peaks of austenite ( γ phase) and the {101} ε of martensite ( ε phase) were selected as they do not overlap each other and have sufficient intensity. The quantitative metallography was used to verify the X ray measured results. The results indicate that the relationship between the volume fraction of stress induced martensite and strain accords with the exponential function, f hcp =1-exp{- β [1-exp(- αη)] n }, suggested by Olsen and Cohen for Fe Cr Ni alloy. The fitted parameters α、β and n are 12.5, 2.2 and 0.5 respectively, among which the n is remarkably different from that of the Fe Cr Ni alloys ( n= 4.5). As a consequence, compared to the Fe Cr Ni alloy, a large amount of SIM can be induced by a relatively low strain in Fe Mn Si based alloys owing to their different phase transformation mechanisms. The present work also confirms the Olsen and Cohen's conclusion that the complete martensite can not be obtained by the stress at temperatures above M s.