采用深冷异步轧制提高高熵合金颗粒增强铝基复合材料的力学性能

为了获得更高性能的铝基复合材料(AMCs),采用室温异步轧制(AR,298 K)和深冷异步轧制(ACR,77 K)制备高熵合金颗粒增强铝基复合材料带材。通过拉伸实验、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对铝基复合材料的力学性能和微观结构进行分析。结果表明,深冷异步轧制比室温异步轧制更能提高复合材料的力学性能。深冷异步轧制含3%(质量分数)高熵合金颗粒的铝基复合材料的抗拉强度达到253 MPa,比室温异步轧制复合材料提高13.5%。与室温异步轧制相比,深冷异步轧制的复合材料具有更少的微孔洞、更细小的晶粒尺寸和更高的位错密度。深冷异步轧制复合材料微缺陷的减少是因为铝基高熵合金颗粒复合材料在深冷环境中具有合适的体积收缩效应。

Achieving High Strength and Tensile Ductility in Pure Nickel by Cryorolling with Subsequent Low-Temperature Short-Time Annealing

Ultra fine-grained pure metals and their alloys have high strength and low ductility.In this study,cryorolling under different strains followed by low-temperature short-time annealing was used to fabricate pure nickel sheets combining high strength with good ductility.The results show that,for different cryorolling strains,the uniform elongation was greatly increased without sacrificing the strength after annealing.A yield strength of 607 MPa and a uniform elongation of 11.7%were obtained after annealing at a small cryorolling strain(ε=0.22),while annealing at a large cryorolling strain(ε=1.6)resulted in a yield strength of 990 MPa and a uniform elongation of 6.4%.X-ray diffraction(XRD),transmission electron microscopy(TEM),scanning electron microscopy(SEM),and electron backscattered diffraction(EBSD)were used to characterize the microstructure of the specimens and showed that the high strength could be attributed to strain hardening during cryorolling,with an additional contribution from grain refinement and the formation of dislocation walls.The high ductility could be attributed to annealing twins and micro-shear bands during stretching,which improved the strain hardening capacity.The results show that the synergistic effect of strength and ductility can be regulated through low-temperature short-time annealing with different cryorolling strains,which provides a new reference for the design of future thermo-mechanical processes.

轧制(热轧,冷轧,深冷轧制)复合法制备轻质金属层状带材研究进展

由于兼具多种材料的综合优势,金属层状复合板得到了广泛关注。轧制复合法具有可稳定连续生产的优势,已成为目前制备金属层状复合板的主要方法之一。本文介绍轧制复合金属层状复合板的研究进展,主要包括热轧复合法、冷轧复合法、累积叠轧法和深冷轧制复合法。系统地讨论金属层状复合板的界面形成机理及影响界面结合质量的主要因素,并对高性能金属层状复合板未来发展方向提出指导性的展望。

深冷轧制与时效处理Al−3.6Cu−1Li合金的显微组织演变和力学性能

对Al−3.6Cu−1Li合金进行室温轧制和深冷轧制,并研究工艺对材料显微组织演变和力学性能的影响。通过显微组织分析与力学性能测试,研究厚度压下率为70%和90%的室温轧制和深冷轧制样品的显微组织和时效特性。经过90%厚度压下率的深冷轧制样品具有高强度和良好的韧性,这主要是由于深冷轧制样品对动态回复的抑制和高密度位错的积累。人工时效研究结果表明,达到峰值硬度的温度与变形量成反比,与轧制温度成正比。此外,明场透射电子显微镜照片表明,时效处理的深冷轧制样品存在T1(Al2CuLi)相析出。研究表明,高存储的应变能增强合金的时效动力学,进而促进强化相形核。

深冷异步轧制制备高力学性能CrCoNi中熵合金

为了获得具有更好强塑性平衡的CrCoNi中熵合金,采用冷轧、异步轧制、深冷轧制和深冷异步轧制4种工艺对中熵合金CrCoNi进行加工,并对合金进行不同温度的退火处理。研究结果表明:深冷异步轧制的合金获得超过1.6 GPa的高强度,当经过1073 K的退火处理后,在具有接近60%的伸长率的同时,仍然保留接近1 GPa的强度。采用深冷异步轧制和退火后,得到较室温异步轧制更为明显的异质特征,这使材料具有更高的强度与更好的塑性。

7075铝合金深冷轧制及时效处理微观组织和性能

采用深冷轧制和室温轧制及峰值时效处理制备了不同厚度的7075铝合金板材,利用硬度测试、拉伸试验、X射线衍射、扫描电子显微镜和透射电子显微镜分析了轧制板材的力学性能和微观组织演变。结果表明:与室温轧制板材发生了严重边裂不同,深冷轧制板材始终未发生边裂。轧制强化效果随压下率增加而提高,80%压下率的深冷轧制样品屈服强度和抗拉强度较固溶样品分别提高155%和44%。深冷轧制样品在峰值时效后强度和塑性同时提升。20%、40%、60%和80%压下率的深冷轧制+峰值时效样品与室温轧制+峰值时效样品相比,断裂伸长率分别提高8.7%、18.5%、45.5%和57.4%,这是时效引起的位错湮灭、深冷轧制更均匀的变形和深冷轧制+峰值时效样品中细小析出相的共同作用。

累积叠轧和深冷轧制复合工艺制备超细晶1060铝合金带材

采用5道次累积叠轧制备超细晶粒1060铝合金带材,并对材料分别进行三道次冷轧(298 K)、深冷轧制(轧制温度为83K和173K)。采用透射电子显微镜检查样品的显微组织,并通过拉伸试验和显微硬度试验测量材料的力学性能。结果表明,在随后的轧制过程中,累积叠轧带材的晶粒尺寸进一步细化,并且随着轧制温度的降低,晶粒尺寸变得更细。深冷轧制(83 K)后带材的晶粒尺寸从累积叠轧样品的666 nm细化至266 nm,这比经过随后冷轧(346 nm)的晶粒尺寸更加细小。同时,与冷轧相比,随后的深冷轧制使超细晶带材具有更高的强度和延展性。

Low-temperature superplasticity of cryorolled Ti-6Al-4V titanium alloy sheets

To investigate the superplastic deformation behavior of cryorolled Ti-6Al-4V titanium alloy,tensile tests were carried out at760℃and 830℃with different strain rate.The evolution of grain and micro structure has been studied using transmission electron microscopy and electron backscatter diffraction.When the tensile temperature was 760℃(<0.5T_(m),T_(m)is absolute melting point of alloy.)and the strain rate was 5×10^(-4)s^(-1),the fracture elongation of the sample reached 385%,showing good low-temperature superplasticity.Compared with the tensile temperature of 760℃,the fracture elongation of the s ample at 830℃was lower due to grain coarsening and oxidation.The strain rate sensitivity value m of all samples was larger than0.3,which confirmed that the cryorolled Ti-6A1-4V titanium alloy with a non-equiaxed grains structure can achieve high superplasticity at a temperature lower than 0.5T_(m),and indicated that the main deformation mechanisms in the tensile test at760-830℃were grain rotation and grain boundary sliding.After the tensile test,the average grain size of all samples was less than 5μm,in which significant dynamic recrystallization and recovery occurred.

Fabrication and Characterization of High-Bonding-Strength Al/Ti/Al-Laminated Composites via Cryorolling

Sandwich-like Al/Ti/Al-laminated composites have many advantages such as low density and high specific strength with value in mechanical manufacturing and aerospace engineering. Here, Al/Ti/Al-laminated composites were fabricated by hot roll bonding and subsequent processes: cryorolling(-190 ℃ and-100 ℃), cold rolling(25 ℃), and hot rolling(300 ℃). Their bonding strength and mechanical properties were then studied by an Autograph AGS-X universal electronic testing machine. The results show that cryorolling can improve the interface bonding strength and tensile strength of Al/Ti/Allaminated composites. For the Al/Ti/Al-laminated composites subjected to cryorolling at-100 ℃, they have the highest strength near 260 MPa—this is 48 MPa and 41 MPa higher than the laminated composites subjected to cold and hot rolling, respectively. These results also show the strongest peeling strength. Finally, the mechanisms of the enhancement of bonding strength and mechanical properties of Al/Ti/Al-laminated composites subjected to cryorolling were mainly discussed.

Suppressing Al2O3 nanoparticle coarsening and Cu nanograin growth of milled nanostructured Cu-5vol.%Al2O3 composite powder particles by doping with Ti

Both the coarsening of Al2O3 nanoparticles and the growth of Cu nanograins of mechanically milled nanostructured Cu-5 vol.%Al2O3 composites with, and without, trace amounts of Ti during annealing at973 K for 1 h were investigated. It was found that doping with a small amount of Ti（e.g. 0.2 wt%） in a nanostructured Cu-5 vol.%Al2O3 composite effectively suppressed the coarsening of Al2O3 nanoparticles during exposure at this temperature. Further, the Ti addition also prevented the concomitant abnormal growth of the copper grains normally caused by the coarsening of the Al2O3 nanoparticles. Energy dispersive X-ray spectroscopy analysis of the Al2O3 nanoparticles in the annealed Cu-5 vol.%Al2 O3-0.2 wt%Ti sample suggested that the Ti atoms either diffused into the Al2O3 nanoparticles or segregated to the Cu/Al2O3 interfaces to form Ti-doped Al2O3 nanoparticles, which was more stable than Ti-free Al2O3 nanoparticles during annealing at high homologous temperatures.

Enhanced Mechanical Properties of AA5083 Matrix Composite via Introducing Al_(0.5)CoCrFeNi Particles and Cryorolling

High-entropy alloy particles(HEAPs)can markedly enhance the mechanical properties of metal matrix composites(MMCs).In this study,AA5083/Al_(0.5) CoCrFeNi HEAPs MMCs with diff erent HEAPs contents(0,1,and 3 wt%)were prepared via a stir-casting,and then these MMCs sheets were hot rolled(573 K)and cryorolled(77 K),respectively.The mechanical properties of the MMCs sheets were measured by tensile testing and microhardness test.Additionally,their microstructures were analyzed by scanning electron microscopy and transmission electron microscopy.Results revealed that the ultimate tensile strength(UTS)of the as-cast AA5083/Al_(0.5) CoC rF eN i HEAPs MMCs were improved from 203 to 257 MPa by adding 3 wt%HEAPs.And the mechanical properties of the MMCs sheets were improved after cryorolling.After cryorolling with 50%rolling reduction ratio,the MMCs with 1 wt%HEAPs had an UTS of 382 MPa,which was 1.9 times that of the MMCs before rolling.Finally,the strengthening mechanisms of HEAPs and cryorolling on the AA5083/HEAPs MMCs were discussed.