Strong and precise compact produced by giving high plastic energy to powder

在粉末冶金烧结过程中，绿色压坯中存在空位，导致压坯变形，降低了压坯强度。如果契约没有空缺，上述问题就会减少。本研究旨在借由赋予粉末高塑性能，以获得无空位的完美压坯。设计了新的方法，并阐明了以下几点.压缩和扭转压制工业纯铝粉在双模具装置上进行压缩和扭转。一个模具是固定的，另一个是旋转的，这些模具相互之间的拉力很大。因此，在模具之间设置的粉末得到高压和严重的扭曲。结果表明：（1）在600 MPa的模压力下，充模效率达到95%的高值; (2)当模具压力为312 MPa时，无扭曲压坯的拉伸强度仅为2 MPa。随着模具的旋转，强度增加，当模具旋转4PI弧度（滑动行程约60 mm）时，强度达到22 MPa，是原来的10倍.当粉末与模具之间的摩擦力过大时，粉末不能被向后挤压。此时，如果容器模向后移动，则粉末将借助于粉末和容器模之间的向外摩擦力从容器模和冲头之间的狭窄空间挤出。该方法表明：（1）无论压制条件如何，为使粉末成形，最低冲压压力约为300 MPa。(2)拉伸强度变为144 MPa的高值，其与轧制板的拉伸强度相当。(3)通过显微分析证实了粉末被良好压制的原因。

In the sintering of powder metallurgy, the vacancy left in the green compact causes the form change and lowers the strength. If the compact has no vacancy, the above problems will diminish. This study aims to produce perfect compact of no vacancy by giving high plastic energy to powder. New methods were designed, and the followings were clarified.1. Compress and Twist CompactingCommercially pure aluminum powder was compressed and twisted by the apparatus with two dies. The one die is fixed and the other rotates, and these dies pull against strongly each other. So, the powder set between the dies gets high pressure and severe twist. The followings were found: (1) The charge efficiency became high value of 95% at the die pressure of 600 MPa. (2) The tensile strength of the compact with no twist was only 2 MPa when the die pressure was 312 MPa. The strength increased according as the rotation of die, and became 22 MPa, which was 10 times bigger, at the rotation of 4PI radian (Sliding travel about 60 mm).2. Friction-aided Backward Extrusion Powder can not be extruded backward if the friction between the powder and dies is so large. At this time, if the container die is moved backward, the powder will be extruded from the narrow space between the container die and a punch by the aid of outward friction force between.the powder and the container die. This method showed the followings: (1) To give a form to the powder, the lowest punch pressure needed about 300 MPa irrespective of compacting condition. (2) The tensile strength became high value of 144 MPa which was comparable to that of a rolling sheet. (3) The reason why the powder was compacted well was confirmed by the microscopic analysis.