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The influences of pre-ageing temperature and natural ageing time on subsequent artificial age hardening behavior and precipitation sequence of new type Al-1.01Mg-0.68Si-1.78Cu alloy were investigated by hardness test, differential scanning calorimetry (DSC) test and transmission electronic microscopy (TEM) observations. When pre-ageing temperature is 20℃ (natural ageing), the peak hardness of subsequent artificial aged alloy is lower than that of T6 treated alloy (negative effect), while a positive effect appears when pre-ageing temperature is above 80℃. The size of needlelike β-precipitate in subsequent artificial aged alloy is much coarser when pre-ageing temperature is 20℃, which causes a decrease in peak-hardness. The positive effect occurs again when natural ageing time is longer than 3 weeks. There are seven exothermic peaks in DSC curve of as-quenched alloy, while the number and height of exothermic peak decrease with increasing pre-ageing temperature and natural ageing time.
The influences of pre-aging temperature and natural aging time on subsequent artificial aging hardening behavior and precipitation sequence of new type Al-1.01Mg-0.68Si-1.78Cu alloys were investigated by hardness test, differential scanning calorimetry (DSC) test and transmission electronic microscopy (TEM) observations. When pre-aging temperature is 20 ℃ (natural aging), the peak hardness of subsequent artificial aged alloys is lower than that of T6 treated alloy (negative effect), while a positive effect appears when pre-aging temperature is above 80 ° C. The size of needlelike β-precipitate in subsequent artificial aged alloy is much coarser when pre-aging temperature is 20 ° C, which causes a decrease in peak-hardness. The positive effect occurs again when natural aging time is longer than than 3 weeks. There are seven exothermic peaks in DSC curve of as-quenched alloy, while the number and height of exothermic peak decrease with increasing pre-aging temperature and natural aging t ime.