The development of modern science and technology has imposed stricter requirements on structural metal materials. On the one hand, it is expected that the material is lighter to meet the demand for lightweighting; on the other hand, it is also expected that the material can withstand higher temperatures to ensure service safety at high power / high power. But usually the safety service temperature of metal materials and the material density show an inverse relationship, so that the choice of materials is often lost. In particular, many parts / components in important fields such as aerospace, transportation, and military weapons today have service temperatures gradually ranging from 250 ° C to 400 ° C, but the corresponding lightweight alloy materials are difficult to withstand their "high temperature" . Compared to other lightweight metal materials, aluminum alloys are the most promising light alloys for use in this temperature range. However, in the traditional aluminum alloy, the nano-secondary particles on which it is strengthened will be severely coarsened at a temperature above 250 ° C, and the strengthening effect will be seriously lost. In the case of high-temperature creep with simultaneous applied stress, the traditional aluminum alloy material will rapidly soften and cause ultimate instability. How to improve the high-temperature stability of nano-second phase particles, and then improve the high-temperature creep resistance of aluminum alloys, has become a difficult problem for aluminum alloys and even light alloy systems.
Recently, PhD students Gao Yihan, Yang Chong and Young Teacher Zhang Jinyu from the State Key Laboratory of Metal Material Strength of Xi'an Jiaotong University, under the guidance of Professor Liu Gang and Professor Sun Jun, and cooperated with Professor Marx of Johns Hopkins University and Professor Cao Lingfei of Chongqing University in A breakthrough was made in the research and development of high temperature creep aluminum alloy materials. They are based on the microstructure design idea of atomic segregation at the interface of nanosecond phase particles. By analyzing the interactions between different solute atoms at the atomic level, and using related thermodynamic / kinetic analysis, they choose common Al-Cu alloys in combination with Sc The element's microalloying effect, under the clever heat treatment process, achieves a high concentration segregation of Sc atoms at the interface of the Al2Cu reinforced phase particles, which is equivalent to putting a "coat" on the Al2Cu reinforced phase particles, significantly inhibiting The particles grow coarse at high temperatures. At the same time, additional stable Al3Sc particles were precipitated, which made the two types of strengthening phase particles that did not originally precipitate in the same aging temperature range coexist in harmony. This microstructure becomes ordinary Al-Cu alloy is no longer ordinary, but has extraordinary high temperature creep resistance: in the severe creep environment of 300oC and external stress greater than 30MPa, it can be safely used for more than 350 hours ; If the applied stress is below 20MPa, the creep life can exceed 2000 hours. Aluminium alloys (including Al-Cu-Mg series, Al-Mg-Si series, Al-Zn-Mg series, Al-Si series and Al-Sc series) and aluminum alloy composite materials (added ceramic Compared with two-phase particles (such as Al2O3 and SiC), the high temperature creep performance of the new Al-Cu-Sc alloy is improved by 2-3 orders of magnitude under the same service conditions.