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一九八四年末,对锻件进行生产检查时,发现LD5合金的模锻件淬火人工时效后,在锻件边部粗晶区处发现裂纹。经显微组织检查,低倍观察到的裂纹并未裂开,只是在粗晶区晶界上有黑色串珠形缺陷。这种缺陷的性质没有一致意见,有人认为是裂纹,有人认为类似过烧,也有人认为是挤压过程中挤压缺陷残留等。国产铝合金生产以来,虽然遇到过这种缺陷,但是一直没有研究清楚。在现行的质量标准中,也没有判断该缺陷产品报废的依据。为研究缺陷的性质,决定其产品能否使用,特做了如下实验。
In late 1984, forgings for production inspection, it was found that the die forgings of LD5 alloy quenching artificial aging, found in the edge of the forged grain area at the crack. The microscopic examination showed that the cracks observed at low magnification did not crack, but had a black beaded defect at the grain boundary of the coarse grain region. There is no consensus on the nature of this defect, some people think it is a crack, some people think it is similar to over burning, and others think that it is squeezed during the extrusion process and so on. Since the production of domestic aluminum alloy, although encountered such a defect, but has not been studied clearly. In the current quality standards, there is no basis for judging the defective products scrapped. In order to study the nature of defects and determine the availability of their products, the following experiment was done.