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采用第一原理赝势平面波方法研究了Cr在B2-TiAl完整与缺陷晶体中的择优占位趋势,并基于虚拟晶体近似(VCA)与Born稳定性判据,计算了Cr合金化(浓度<22.0%,原子分数,下同)完整与缺陷B2-TiAl晶体的弹性性质和Cr稳定β相的合金化浓度,进而采用Cauchy压力参数(c12-c44)、杨氏模量E、剪切模量G及其与体模量B的比值G/B表征和评判了Cr浓度对β-TiAl-x Cr多晶合金强韧化效果的影响。结果表明:B2-TiAl晶体的点缺陷结构主要为Ti反位,Cr在B2-TiAl完整与缺陷晶体中都优先占据Al原子位。在化学计量比β-Ti50Al50-xCrx合金与富Ti的β-Ti56Al44-xCrx合金中稳定β相的Cr合金化浓度分别为10%~15%和9%~20%。对于化学计量比β-Ti50Al50-xCrx(x=10~15)合金,Cr合金化可显著提高其强度与硬度,且浓度越高强化效果越好,但不存在明显的韧化效果;对于富Ti的β-Ti56Al44-xCrx(x=9~20)合金,合金塑性与韧性随Cr合金化浓度增加而变好,但Cr合金化的强化作用则不明显。
The first principle of pseudopotential plane wave method was used to study the preferential occupancy of Cr in the complete and defective B2-TiAl crystals. Based on the VCA and Born stability criteria, the Cr alloying (concentration <22.0 %, Atomic fraction, the same below) the elastic properties of the complete and defective B2-TiAl crystals and the alloying concentration of the stable β phase of Cr, followed by the Cauchy pressure parameter (c12-c44), the Young’s modulus E, the shear modulus G And the ratio of G / B to B were used to characterize and evaluate the effect of Cr concentration on the toughening effect of β-TiAl-xCr polycrystalline alloys. The results show that the point defect structure of B2-TiAl crystal is mainly Ti anti-phase, and Cr preferentially occupies Al atomic site in the B2-TiAl complete and defect crystal. The alloying Cr concentrations of the stable β phase in the stoichiometric β-Ti50Al50-xCrx alloy and the Ti-rich β-Ti56Al44-xCrx alloy are 10% -15% and 9% -20%, respectively. For the alloy with stoichiometric ratio of β-Ti50Al50-xCrx (x = 10-15), Cr alloying can significantly increase the strength and hardness, and the higher the concentration, the better the strengthening effect, but there is no obvious toughening effect; Β-Ti56Al44-xCrx (x = 9-20) alloy. The plasticity and toughness of the alloy become better with the increase of Cr alloying concentration, but the strengthening effect of Cr alloying is not obvious.