Continuous cooling precipitation diagram of high alloyed Al-Zn-Mg-Cu 7049A alloy

The precipitation behaviour during cooling from solution annealing of high alloyed 7049A aluminium alloy was investigated, covering the complete cooling-rate-range of technical interest. This ranges from slow cooling rates close to equilibrium up to rates above complete supersaturation and is covering seven orders of magnitude in cooling rate （0.0005 to 5000 K/s）. The continuous cooling precipitation behaviour of 7049A alloy was recorded by combining different differential scanning calorimetry （DSC） techniques and microstructure analysis by SEM and Vickers hardness testing. The high alloyed, high strength and quench sensitive wrought aluminium alloy 7049A was investigated during quenching from solution annealing by conventional DSC in the cooling rate range of 0.0005 to 4 K/s. In this range at least two exothermal precipitation reactions were observed： a high temperature reaction in a narrow temperature interval of 450-430℃, and a low temperature reaction in a broad temperature interval down to about 200 ℃. Intensities of both reactions decreased with increasing cooling rate. Quenching from solution annealing with rates up to 1000 K/s was investigated by differential fast scanning calorimetry （DFSC） and the differential reheating method （DRM）. A critical quenching rate to suppress all precipitation reactions of 100-300 K/s was been determined.

含山梨糖醇型成核剂的聚丙烯在高过冷度下的成核活性研究

采用快速差示扫描量热法(FDSC)在高过冷条件下研究了山梨醇型成核剂成核的聚丙烯(PP)的结晶动力学,并将其与注塑零件的光学特性相关联。FDSC用于确定非等温结晶发生的临界冷却速率和快速冷却后等温结晶过程中达到最大结晶速率的时间。研究的成核剂是1,3:2,4-二(3,4-二甲基亚苄基)山梨醇(DMDBS)和1,2,3-三氧基-4,6:5,7-二-O-[(4-丙基苯基)亚-甲基]-壬糖醇(TBPMN)。颗粒成核剂的颗粒数目决定了非均相成核数量,与颗粒成核剂不同,山梨醇型成核剂通过将提前溶解在聚合物熔体中的山梨醇型分子进行相分离而形成自组装纳米原纤维超结构。本文还提出了一种描述成核剂自组装效率的方法。结合雾度数据,确定了两种不同的结晶机理,可理解为高雾度下的三维球晶结晶和低雾度下的一维(棒状或羊肉串状)结晶。