Department of Material Forming, Karaganda State Industrial University, Republic Avenue 30, 101400 Temirtau, Kazakhstan.
Micron. 2013 Jan;44:210-7. doi: 10.1016/j.micron.2012.06.011. Epub 2012 Jul 4.
The presented article deals with the effects of equal channel angular pressing (ECAP) with a newly adjusted die geometry on the microstructure and mechanical properties of the Al-Si-Mn-Fe alloy. This alloy was subjected to two modes of heat treatment followed by the ECAP process, which led to partial back pressure (ECAP-PBP). Ultra-fine grained (UFG) structure formed through ECAP-PBP process has been studied by methods of optical as well as electron microscopy. The obtained results indicate that quenched alloys, in comparison to slowly cooled alloys, do not contain large brittle particles which subsequently initiate a premature creation of cracks. It was shown that the mechanical properties of these alloys after such processing depend first and foremost on the selected type of heat treatment and on the number of performed passes. The maximum of ultimate tensile strength (417 MPa) was obtained for quenched alloy after 3 passes. On the other hand, maximum ductility was found in slowly cooled alloy after second pass. Further passes reduced strength due to the brittle behavior of excluded particles. One of the partial findings is that there is only a small dependency of the resulting size of grains on previously applied thermal processing. The minimum grain sizes were obtained after 3 passages, where their size ranged between 0.4 and 0.8 μm. The application of quick cooling after heat processing due to the occurrence of finer precipitates in the matrix seems to produce better results.
本文研究了新型模具几何形状的等径角挤压（ECAP）对 Al-Si-Mn-Fe 合金的微观结构和力学性能的影响。该合金经过两种热处理模式和 ECAP 工艺（部分反向压力 ECAP-PBP）处理。通过光学和电子显微镜研究了 ECAP-PBP 工艺形成的超细晶（UFG）结构。结果表明，与缓慢冷却的合金相比，淬火合金中不含随后引发早期裂纹的大脆性颗粒。研究表明，经过这种处理的合金的力学性能首先取决于所选的热处理类型和进行的道次数。经过 3 次挤压，淬火合金的最大拉伸强度（417 MPa）最高。另一方面，在第二次挤压后，缓慢冷却的合金具有最大的延展性。进一步挤压由于排除颗粒的脆性行为而降低了强度。部分研究结果表明，晶粒的最终尺寸与先前的热加工工艺只有很小的相关性。在 3 次挤压后获得了最小的晶粒尺寸，其尺寸在 0.4 到 0.8 微米之间。由于基体中出现更细的析出物，在热加工后进行快速冷却似乎会产生更好的效果。
