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本文综述Fe—C[1],Fe—X[2]和Fe—X—C[3]面心立方→体心立方(正方)马氏体相变热力学。相变时的自由能变化可表述为△G~(ρ→α)和△G~(α→M)之代数和,△G~(γ→α)用来作为稳定体心结构核胚的能量,而△G~(α→M)是使体心核胚成为马氏体所需的能量。△G~(α→M)应包括:为形成马氏体及邻近奥氏体形变进行切变所需的能量,马氏体内储存的能量——形成位错的应变能和形成孪晶的界面能,邻近马氏体基体中形成位错的应变能以及表面能等。可将相变驱动力简列为:△G~(α→M)=5σ_(ms)+217,其中σ_(ms)为奥氏体在MS时的屈伏强度。由此可直接由热力学计算求得Ms。在Fe—C、Fe—Ni—C及Fe—Cr—C系中所求得的Ms和实验值很好符合,在纯铁、Fe—Ni、Fe—Cr和Fe—Mn中和部分实验值符合,论证部分偏高的Ms值属于Ma或表面马氏体的MS,而不是整块试样真正的Ms。本文对铁基合金马氏体相变热力学作了统一处理,结果得到其热力学性质一致,纠正了过去一些矛盾的或不正确的论点。提出对Fe—X—C系热力学处理式,求得Fe—Ni—C及Fe—Cr—C系的Ms。dMs/dx。因碳在奥氏体活度的减小而增大。dMs/dx随碳及合金含量的增加而增大,由于碳主要决定相变驱动力,因而碳的影响更大。
In this paper, the thermodynamics of the martensitic transformation of Fe-C [1], Fe-X [2] and Fe-X-C [3] The change of free energy during phase transition can be expressed as the sum of △ G ~ (ρ → α) and △ G ~ (α → M), △ G ~ (γ → α) , While △ G ~ (α → M) is the energy required to make the body nuclei nuclei embryo into martensite. △ G ~ (α → M) should include the energy needed to shear the formation of martensite and adjacent austenite, the energy stored in the martensite, the strain energy that forms dislocations, and the interface that forms the twin Can, near the martensite matrix formation dislocation strain energy and surface energy. The driving force of phase transformation can be simply summarized as ΔG ~ (α → M) = 5σ_ (ms) +217, where σ_ (ms) is the yield strength of austenite at MS. This can be calculated directly from the thermodynamic calculation of Ms. Ms found in the Fe-C, Fe-Ni-C and Fe-Cr-C systems is in good agreement with the experimental values and the experimental values were neutralized in the pure iron, Fe-Ni, Fe-Cr and Fe- Compliance, argumentation part of the high Ms value belongs to the Ma or surface martensite MS, rather than a whole sample of the real Ms.. In this paper, the thermodynamics of the martensitic transformation of iron-based alloys are treated in a uniform manner. The results show that the thermodynamics are consistent, and some conflicting or incorrect arguments in the past are corrected. A Fe-Ni-C and Fe-Cr-C-based Ms. Fe-X-C thermodynamic treatment formula was proposed. dMs / dx. Due to the reduction of carbon in the austenite activity increases. dMs / dx increases with increasing carbon and alloy content, and carbon has a greater impact because carbon predominantly determines the driving force for phase change.