Abstract
Short times (5 min. /cycle) cyclic semi-solid heat treating process up to four cycles for 6061 aluminum alloy was studied. The microstructures of as-received and cyclic semi-solid heat treatment at the edge of samples at 630◦C for one to four cycles were investigated.Short time cyclic heat treatment up to two cycles improves the microstructure to be finer and more globular compared with asreceived one. Short time cyclic heat treatment significantly affects the microstructure at the edge of samples only due to short time heating.Optimum values of grain size and grain sphericity at the edge of samples for short cyclic heating time (5 min./cycle) of about 160 μm and 0.57 respectively. Increasing the number of heat treatment cycles above three increases both shrinkage porosity and micro-cracks formation.
Highlights
The required strength of an alloy is concerned by the design that often taken to develop it
Coarsening and cracks defects were appeared for long heating time of 40 and 50 min. Regarding those mentioned above and depending on the previous work [6] recommendations, this work is carried out to study microstructural evolution of 6061 Al Alloy during short heating times (5 min for one to 20 min. for four cycles) cyclic Semi-solid heat treatment to obtain the optimum of grain size and grain sphericity microstructure
It is clear that cyclic semi-solid heat treatment has improved the macrostructure homogeneity of 6061 Al alloy.Microstructure of as- recived 6061alloy at the center, interface and edge of samples respectively is shown in Fig.3.It can be seen that the grains of the as-received 6061 Al alloy clearly exhibits the rosette character for micrograph took for area at the edge and near the edge of specimen but exhibits near spheroid for area at center of specimen
Summary
The required strength of an alloy is concerned by the design that often taken to develop it. The as-obtained microstructure of the material is called T6 temper (tempering around 175 ƕC) Another interesting characteristic of the 6061 Al alloy is its good weldability. Intensive work of semi-solid heat treatments [4,5] is aimed to develop and improve structure and properties of 6061 Al alloy. Previous work [6] on cyclic Semi-Solid Heat Treatment of 6061 Al alloy for long times (10 to 50 min.) have been studied. Cyclic semi-solid heat treatment results in a relatively finer and more globular non-dendrites microstructure compared with isothermal heating one for all heating time conditions (10 to 50 min.). Regarding those mentioned above and depending on the previous work [6] recommendations, this work is carried out to study microstructural (grain size and gain grain sphericity) evolution of 6061 Al Alloy during short heating times (5 min for one to 20 min. for four cycles) cyclic Semi-solid heat treatment to obtain the optimum of grain size and grain sphericity microstructure
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