- 期刊
鋁合金6061於熱間環壓試驗的晶粒粗化研究
Investigation of Grain Coarsening in Aluminum Alloy 6061 by Using Ring Compression Test at Elevated Temperatures
摘要
鋁合金材料在鍛造時，常在鍛件表面出現晶粒粗大的狀況。不僅降低鍛件強度，同時不利後續的表面處理工程。理解晶粒粗大的原因將可供改善的方針。因此，本研究嘗試應用環壓試驗的方法，藉其多變的應變分布及其清晰的摩擦狀態，並施以不同的熱處理，以瞭解晶粒粗化的成因。研究以鋁合金6061為材料，並以田口法將材料溫度、鍛粗速度、壓縮量以及潤滑劑作為在環壓試驗的製程參數。結果顯示影響鍛件晶粒尺寸最鉅者為潤滑劑，其次為鍛造溫度，再次為壓縮量，而鍛粗速度的影響微乎其微。其中以未使用潤滑劑且在500℃下鍛粗，易使鋁合金6061晶粒粗化。至於後續的T4及T6熱處理多能令鋁合金進一步晶粒細化，但二熱處理的結果相差無幾，而以T6熱處理所得者較為細化，且影響二者細化的程度均以壓縮量為最鉅。
並列摘要
Grain coarsening during and after hot forming is very annoying for manufacturing aluminum alloy parts. Not only strength is therefore reduced, but also the subsequent surface treatments are hard to realize. To understand its possible causes is the first step to overcome the annoying grain coarsening in manufacturing aluminum alloy parts. Thus, this study tried to use ring compression test, which can not only reveal the friction coefficient between the specimen but also create versatile deformation in the specimen and therefore provide multifaceted conditions to develop diverse grain size in specimen. The further grain coarsening influenced by subsequent heat treatment was investigated as well. The material used in this study is commercial 6061 aluminum alloy, which is widely used in forging industry. To investigate the possible causes of grain coarsening in aluminum alloys, Taguchi method is applied in this study with four factors such as forming temperature, punch speed, deformation amount, and lubricant regarding the frictional boundary condition between part and tools. As a result, the significant factor to mostly coarsen grain size is lubricant or the frictional boundary condition, which is followed by forming temperature. The less influence on the grain size is the punch speed. Forming 6061 aluminum alloy without lubricant and at 500°C can easily coarsen the grain size, especially in the corners of part, where the material contacts to tool and is also free to contact to tool. The subsequent T4 or T6 treatment can further refine the grains. There are no significant difference between the grain sizes obtained from both treatments. The factor mostly influencing the grain size is deformation.