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在金相分析中,有时为研究某些试样中的第二相或疏松、微裂纹等微观缺陷及裂纹的扩展情况等立体形态或分布特征时,需要测定其厚度方向的尺寸,即需要测出试佯磨抛去除层的厚度,此时,由于用测微仪只能测出试样表面的相对平整程度,对此就显得无能为力了.为此,我们试验开发出了显微硬度计的另一种用途——金相试样磨抛去除层厚度的无基准精确测量.现介绍如下.1 试验方法试样经400目以上金相砂纸精磨后,用压头为136°金刚石角锥的显微硬度计在试样磨面上打一显微压痕,压痕放大后如下图所示.由于压痕形状是与金刚石压头一致的两相对面间夹角α=136°的正四方锥形,它在试样磨面的投影为正方形□ABCD,抛光后则成为□abcd.设该两正方形的边长和对角线长分别为l_0、l_1和d_0、d_1,则它们之间的关系为:
In the case of metallographic analysis, in order to study the three-dimensional morphology or distribution characteristics such as the second phase in some samples, microscopic defects such as looseness and microcracks, and the propagation of cracks, it is sometimes necessary to measure the dimension in the thickness direction, that is, Try to throw away the thickness of the layer removed, at this time, as the micrometer can only measure the relative flatness of the surface of the sample, which seems powerless.To this end, we developed a microhardness tester Another use - Metallographic sample grinding and polishing to remove the thickness of the base without accurate measurement is described below .1 Test Method After the sample over 400 mesh metallurgical sandpaper, with a pressure head of 136 ° diamond pyramid Of the microhardness tester in the sample surface to play a micro-micro-indentation, indentation enlargement as shown below.As the indentation shape is consistent with the diamond indenter the angle between the two opposing surfaces α = 136 ° positive Square pyramidal, the projection of which is square ABCD on the polished surface of the specimen, and then abcd after polishing. Assuming that the length and diagonal length of the two squares are l_0, l_1 and d_0, d_1, respectively The relationship is: