Phase transition and pitting corrosion behaviour for Mo—implanted aluminium

Molybdenum ions are implanted into aluminium with high ion flux and high dose at elevated temperatures of 200℃, 400℃ and 500℃. Due to the high temperature and high flux of vacancies and interstitial atoms, the atom diffusion and chemical effects are enhanced during the ion implantation. The effects increase with increasing ion flux and dose, so that new phase formation and phase transition emerge noticeably. X-ray diffraction analysis shows that when the aluminium is implanted with Mo ions at a low ion flux (25μA/cm²), the Al₅Mo alloy is formed. The atomic ratio of Mo/Al of the Al₅Mo phase is close to 20%. When the aluminium is implanted with Mo ions at a high ion flux (50μA/cm²), the phase transition from Al₅Mo to Al₁₂Mo appears, and the latter is dominant, which is determined to be the final phase. The ratio of Mo/Al in Al₁₂Mo is 7.7%. Rutherford backscattering spectroscopy indicates also that the Mo/Al atom ratio is ～7% to ～8% in Mo-implanted aluminium. The atomic ratios of the constituents in Al₅Mo and Al₁₂Mo are of stoichiometric composition for these alloys. The thicknesses of the Al₁₂Mo alloy layers for Mo-implanted Al with ion doses of 3×10¹⁷/cm² and 1×10¹⁸/cm² are 550nm and 2000nm, respectively. The pitting corrosion potential V_p increases obviously. It is clear that due to the formation of Al₁₂Mo alloy layer, the pitting corrosion resistance is enhanced.     

Al-Zn-Mg-Cu-Li合金时效过程微结构演化的小角x射线散射研究

应用小角x射线散射技术分析了Al-Zn-Mg-Cu-Li合金在130，150和160℃温度时效24 h析出粒子的微结构参数的变化情况. 粒子的半径随着时效温度的增高而增加，它的比内表面积和体积百分数随着时效温度的增高而减小. 对Porod曲线q³J(q)-q²的分析表明,析出粒子与基体之间有明显的界面. 关键词： 小角x射线散射 Al-Zn-Mg-Cu-Li合金 时效 析出粒子