【摘要】 本文利用硬度、光学显微镜和透射电镜研究了微量Ti(0.15％)对Al-5.0Zn-1.8Mg合金的沉淀过程、临界形核温度(T′_c)和显微组织参数的影响.结果表明,微量Ti能显著细化晶粒,但无抑制再结晶和提高T′_c的能力.低温时效(T_a<T′_c=150℃),Ti能抑制MPt的长大,提高其密度和合金的硬度,但高温时效(T_a>T′_c),Ti又有相反的作用,能使MPt显著粗化和降低硬度.但在任一时效温度(120—200℃),含Ti合金的GBP和PFZ均比无Ti合金小和窄.Ti对沉淀过程和组织参数的这种影响,可用Ti原子团参与了GP区形核和含Ti合金过剩空位浓度低的观点来说明.更多还原

【Abstract】 The effect of an additive of 0.15 wt-% Ti in the Al-5.0Zn-1.8Mg alloy upon the precipitation, critical nucleation temperature, T’_c, and structural parameters has been investigated by means of hardness test as well as optical and TEM observations. The results showed that a trace additive of Ti may impel considerably the refinement of the grains of the alloy, but no more inhibition of its recrystallization and increase of T’_c.Ti may retard the growth of MPt, increase the density and the hardness of the alloy under lower temperature aging, namely, T_a <T’_c= 150℃, but it meets with a reverse under T_a>T’_c. Furthermore, at any aging temperature between 120-200℃, the GBP and PFZ of the Ti-containing alloy are always finer and narrower than that of one free from Ti. It seems to be explained that influence of Ti addition on the precipitation and structural parameters would be caused by the participation of the Ti atom clusters in the nucleation of GP zone and the low concentration of excess vacancies in the Ti-containing alloy.更多还原