【作者】 郑强；

【导师】 陈康华；

【作者基本信息】 中南大学 ， 材料学， 2004， 硕士

【摘要】 Al-Zn-Mg系合金及焊接接头具有较高强度,经自然时效,接头强度可接近基材的强度,但该合金应力腐蚀抗力较差。因此发展高强可焊Al-Zn-Mg系铝合金须研究解决合金基材与热影响区的强度与应力腐蚀之间的矛盾。发展合金基材及其焊后热处理工艺是解决这一矛盾的途径之一。 本文研究了不同固溶和时效状态高温预析出对7A52合金基材的时效硬化和应力腐蚀性能的影响。并研究了高温析出对焊接热影响区及后处理应力腐蚀性能的影响。研究结果表明: 1)不同温度固溶和预析出可以改变合金的过饱和度,从而对时效硬化和力学性能产生影响。随固溶温度的提高,淬火后合金的过饱和度增加,因此合金的硬度和强度增加,且高温预析出的作用增强。但固溶温度过高,导致合金应力腐蚀抗力下降。 2)高温预析出可以改变不同时效状态的晶界和晶内的析出相的大小和分布,改善合金的应力腐蚀抗力。经过高温预析出处理后,双级时效比自然时效具有更好的应力腐蚀抗力,三级时效比单级时效具有更好的应力腐蚀抗力。 3)7A52合金焊接热影响区及其后处理研究表明,高温预析出处理铝基材经焊接高温热循环后与无预析出处理的基材相比仍有较高的应力腐蚀抗力。更多还原

【Abstract】 Al-Zn-Mg series alloys and their welding joint have high strength. After welding, the strength of welding joint can be recovered to that of the base metal only by natural aging. However this series alloys have poor stress corrosion resistance. It is necessary to resolve the conflicting problem between the strength of base metal and welding joint and their stress corrosion cracking in order to develop high-strength and wieldable Al-Zn-Mg series alloy. Developing new heat treatment for base metal and its welding joint is a method to resolve this problem.The effects of high temperature pre-precipitation on the base metal of 7A52 alloy were investigated under different solution and aging temperature. The effects of high temperature pre-precipitation on the stress corrosion properties of the heat affected zone were also studied after welding.The results show:1) The degree of super-saturation can be changed by solution and pre-precipitation; therefore, has a great influence on the age-hardening and tensile properties. The alloy will have higher super saturation after quenching from high temperature, so that the alloy will have higher hardness and strength. But if the solution temperature is too high, the stress corrosion resistance will decrease.2) High temperature pre-precipitation can change the size and distribution of the precipitation phase on the grain boundary or in the grain, so that the stress corrosion resistance can be improved. Two-step aging has a better stress corrosion resistance than natural aging and three-step aging is superior to the single stage aging in stress corrosion resistance.3) The heat affected zone and its heat treatment were investigated after undergoing the high temperature heats recycle. The pre-precipitation treatment has better stress corrosion resistance than that treatment withoutpre-precipitation.更多还原