2618铝合金支座等温成形锻件的粗晶问题

Coarse grain problem in isothermal forming forgings for 2618 aluminum alloy support

2618铝合金因其耐热性能良好、热状态下塑性好、塑性变形时工艺性能好,而被广泛应用于航空航天工业。然而,在塑性变形时,由于2618铝合金抑制晶粒长大的微量元素含量较少,致使锻件易出现粗晶问题,使得材料力学性能下降,影响锻件质量。分别使用了国内生产的Φ165 mm和国外进口的Φ160 mm两种2618铝合金原始棒料,采用等温成形技术锻造2618铝合金支座锻件。研究发现,以国内生产的Φ165 mm的2618铝合金挤压棒料为原料的支座锻件在进行热处理后出现了明显的粗晶,通过等比例实物研究原始来料的等温模锻和热处理全过程,发现国内生产的Φ165 mm的2618铝合金原始棒料在去除粗晶环后外缘还存在3~5 mm的亚晶组织,该组织为过渡组织,会在加热时迅速长大为粗晶,必须提前切除。基于此,提出了一种解决粗晶问题的方法,并获得了晶粒尺寸符合要求的支座锻件,为2618类铝合金锻件粗晶问题的解决提供了一种有效方法。

2618 aluminum alloy is widely used in the aerospace industry because of its good heat resistance, good plasticity in hot state and good process performance during plastic deformation. However, due to the low content of trace elements that inhibit grain growth in 2618 aluminum alloy, the forgings often suffer from coarse grain problem during plastic deformation resulting in reducing the mechanical properties and affecting the quality of forgings. Therefore, two kinds of 2618 aluminum alloy original bars, namely, Φ165 mm produced in China and Φ160 mm imported from abroad, were used respectively, and the 2618 aluminum alloy support forgings were forged by isothermal forming technology. The research results show that the support forgings made of Φ165 mm 2618 aluminum alloy extruded bar produced in China has obvious coarse grains after heat treatment, and the whole process of isothermal die forging and heat treatment of the original materials was studied by the actual forgings in proportion. It is found that the Φ165 mm 2618 aluminum alloy original bar produced in China has a subcrystalline structure of 3-5 mm at the outer edge after the coarse grain ring is removed, which is a transitional structure that quickly grows into coarse grains when heated, and it must be removed in advance. Based on this, a solution is proposed to solve the coarse grain problem, and the support forgings with the grain size meeting the requirements are obtained, which provides an effective method for solving the coarse grain problem of 2618 aluminum alloy forgings.