一般工業軋延用鋁材形狀為矩形形狀，軋延過程中所產生的應變大致皆集中在軋延面上，而在材料中心部份其差排密度與儲存能小於軋延表面。因此在此形狀下軋延為一不均勻的塑性變形。此因素會造成一軋延鋁材內部再結晶完成百分比有軋延表面高於中心部份的現象產生，使得軋延結晶結構等軸性不均的現象。本實驗主要改變鋁合金軋延塊材的形狀，由傳統的矩形改變為梯形形狀，其目的在經過軋延後，梯形鋁材在中心部份有較大的塑性變形量，使得軋延試片各部份之變形達到均勻變形，也使材料中心部份產生高差排密度及儲存能。在再結晶過程，材料內部晶粒尺寸大小能呈現等軸均一化。由實驗結果可知，不同形狀的鋁合金塊材在經過相同熱處理時間及溫度下，鋁合金塊材形狀為梯形的試片，其晶粒組織大多以等軸晶方式排列；而矩形形狀塊材的鋁合金中心部分的晶粒有明顯拉長的晶粒，而其他區域的晶粒則為等軸晶。 In a conventional hot-rolled 5038 al-Alloy thick plate, the crystalline structure at the central part in the thickness direction comprises primarily slender grains. However, the grain structure is always equiaxed near the surface of the rolling plate. In this experiment, the shape of the slab before hot rolling was changed to a trapezoid. A main goal is to increase the amount of plastic strain, increasing the dislocation density in the central part of the plate hot-rolled from the trapezoidal aluminum slab. The experimental results indicated that, according to TEM observations, the center of the plate of hot-rolled trapezoidal slab had a higher dislocation density than the center of the rectangular slab. Subsequently, heat treatment caused the treated grains to become equiaxed. Therefore, an equiaxed grain structure that was uniform in the thickness direction of a hot-rolled thick plate could be obtained because the hot rolling of the trapezoidal slab caused profound lateral strain, in addition to extensive deformation in the rolling direction. The excess deformation resulted in a high dislocation density in the central region of the as-hot rolled plate, increasing the strain energy that was stored for recrystallization.