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研究了所有有技术价值的冷却速率范围内7049A铝合金的析出行为。冷却速率从接近平衡冷却时的慢速条件变化到形成完全超饱和固溶体的高速率,跨越了7个数量级(0.0005到5000 K/s)。7049A铝合金连续冷却析出行为采用差热分析(DSC)、扫描电镜(SEM)和维氏硬度测量相结合的方法记录。冷却速率在0.0005到4 K/s时,对高合金化、高强度和高淬火敏感性的变形铝合金7049A从固溶温度下的淬火析出行为采用传统的DSC方法研究。在此冷却速率范围内,至少观察到了两个放热反应:一个是在很窄的温度区间430~450°C内的高温反应;另外一个是最低到200°C且范围很宽的低温反应。这两个反应的强度随着冷却速率的增高而降低。采用快速差热分析(DFSC)和差分再加热方法(DRM)对合金淬火冷却速率从慢速到数千K/s时的析出行为进行了研究。该合金不析出沉淀相时的临界淬火速率为100~300 K/s。
The precipitation behavior of all 7049A aluminum alloys was investigated for all technically valuable cooling rates. Cooling rates vary from slow conditions near equilibrium cooling to high rates to form fully supersaturated solid solutions, spanning seven orders of magnitude (0.0005 to 5000 K / s). The continuous cooling and precipitation behavior of 7049A aluminum alloy was recorded by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and Vickers hardness measurement. When the cooling rate was between 0.0005 and 4 K / s, the conventional DSC method was used to study the quenching and precipitation behavior of the deformed aluminum alloy 7049A with high alloying, high strength and high quenching. Within this cooling rate, at least two exothermic reactions were observed: one at a high temperature of 430-450 ° C in a very narrow temperature range and the other at a very low temperature of 200 ° C in a wide range. The intensities of these two reactions decrease as the cooling rate increases. The precipitation behavior of the alloy during quenching and cooling rate from slow to several thousand K / s was studied by using rapid differential thermal analysis (DFSC) and differential reheating (DRM). The critical quenching rate of the alloy without precipitate phase is 100 ~ 300 K / s.