叠加层数对工业纯铝板材累积叠轧焊合的影响

在室温、无润滑及总压下量相同的条件下,分别采用每道次两层叠轧和每道次三层叠轧的工艺对退火态AA1070工业纯铝板材进行了累积叠轧焊合试验,比较了最终板材界面焊合、织构和力学性能的差别。结果表明,与两层叠轧工艺相比,通过三层叠轧工艺所制备的板材金属层之间焊合状况更好,具有较强的剪切织构和轧制织构,表现出较高的伸长率和较低的抗拉强度,具有较好的综合力学性能。这些差别主要归结于三层叠轧条件下较大的道次压下量和有效剪切变形。

大直径风塔法兰异型环锻件双件合轧工艺模拟与试验

针对大型风塔法兰异型截面环锻件轧制时出现不平稳,外表面径向拉缩等缺陷,提出了双件合轧的轧制工艺。在有限元模拟的基础上,确定了最佳的辗扩预成形毛坯形状,并得到生产验证。结果表明:双件合轧工艺比单件轧制工艺的过程更平稳,充型更完整,且节约近10%的原料,同时提高了生产效率。

5000 mm轧机组合式机架拉杆尺寸优化设计

以某5000 mm组合式粗轧机测量数据作为原始数据,采用基于遗传算法的多目标优化设计理论,在Ansys Workbench优化模块下进行优化分析。将拉杆尺寸作为设计变量,将机架等效应力、窗口变形、横梁与立柱开裂间隙及机架纵向变形作为目标函数对拉杆尺寸进行了优化分析与对比,最终得出使机架具有最佳力学性能的拉杆的最佳尺寸。其中1、2号拉杆最优直径为Φ346 mm,3、4号拉杆最优直径为Φ227 mm,5、6号拉杆最优直径为Φ236 mm,7、8号拉杆最优直径为Φ332 mm。同时得到在拉杆最佳尺寸下机架最大等效应力为112 MPa,窗口最大变形量为0.18 mm,横梁与立柱开裂间隙最大值为0.06 mm,机架纵向总变形为2.7 mm。与整体式机架力学性能进行比较,组合式机架窗口最大变形量减小61%,机架强度明显提高。

Bonding enhancement of cold rolling TA1 P-Ti/AA6061 composite plates via surface oxidation treatment

TA1 P-Ti/AA6061 composite plate was produced by oxidizing the surface of the titanium plate and adopting a cold roll bonding process.The results revealed that the oxide film(Ti6O)prepared on the surface of TA1 pure titanium was easy to crack during the cold roll bonding,thereby promoting the formation of an effective mechanical interlock at the interface,which can effectively reduce the minimum reduction rate of the composite plates produced by cold rolling of titanium and aluminium plates.Moreover,the composite plate subjected to oxidation treatment exhibited high shear strength,particularly at a 43%reduction rate,achieving a commendable value of 117 MPa.Based on oxidation treatment and different reduction rates,the annealed composite plates at temperatures of 400,450,and 500°C displayed favorable resistance to interface delamination,highlighting their remarkable strength-plasticity compatibility as evidenced by a maximum elongation of 31.845%.

Influence of thermomechanical treatment on recrystallization and softening resistance of Cu-6.5Fe-0.3Mg alloy

The recrystallization and softening resistance of a Cu-6.5Fe-0.3Mg(mass fraction,%)alloy prepared by Process 1(cold rolling heat treatment)and Process 2(hot/cold rolling heat treatment)were studied using Vickers hardness tests,tensile tests,scanning electron microscopy and transmission electron microscopy.The softening temperature,hardness and tensile strength of the alloy prepared by Process 2 were 110°C,HV 15 and 114 MPa higher,respectively,than those of the alloy prepared by Process 1 after aging at 300°C.The recrystallization activation energy of the alloys prepared by Process 1 and Process 2 were 72.83 and 98.11 kJ/mol,respectively.The pinning effects of the precipitates of the two alloys on grain boundaries and dislocations were basically the same.The softening mechanism was mainly attributed to the loss of dislocation strengthening.The higher Fe fiber density inhibited the average free migration path of dislocations and grain boundary migration in the alloy,which was the main reason for higher softening temperature of the alloy prepared by Process 2.

Ultrahigh strength and improved electrical conductivity in an aging strengthened copper alloy processed by combination of equal channel angular pressing and thermomechanical treatment

In this paper,equal channel angular pressing and thermomechanical treatment was employed to improve the strength and electrical conductivity of an aging strengthened Cu-Ti-Cr-Mg alloy,and the microstructure and properties of the alloy were investigated in detail.The results showed that the samples deformed by the combination of cryogenic equal channel angular pressing(ECAP)and rolling had good comprehensive properties after aging at 400℃.The tensile strength of the peak-aged and over-aged samples was 1120 MPa and 940 MPa,with their corresponding electrical conductivity of 14.7%IACS and 22.1%IACS,respectively.ECAP and cryogenic rolling introduced high density dislocations,leading to the inhibition of the softening effects and refinement of the grains.After a long time aging at 400℃,the alloy exhibited ultra-high strength with obvious increasing electrical conductivity.The high strength was attributed to the synergistic effect of work hardening,grain refinement strengthening and precipitation strengthening.The precipitation of a large amount of Ti atoms from the matrix led to the high electrical conductivity of the over-aged sample.

Effect of annealing temperature on microstructure and mechanical properties of Mg-Zn-Zr-Nd alloy with large final rolling deformation

In this study,the Mg-3Zn-0.5Zr-χNd(χ=0,0.6)alloys were subjected to final rolling treatment with large deformation of 50%.The impact of annealing temperatures on the microstructure and mechanical properties was investigated.The rolled Mg-3Zn-0.5Zr-0.6Nd alloy exhibited an ultimate tensile strength of 386 MPa,a yield strength of 361 MPa,and an elongation of 7.1%.Annealing at different temperatures resulted in reduced strength and obviously increased elongation for both alloys.Optimal mechanical properties for the Mg-3Zn-0.5Zr-0.6Nd alloy were achieved after annealing at 200℃,with an ultimate tensile strength of 287 MPa,a yield strength of 235 MPa,and an elongation of 26.1%.The numerous deformed microstructures,twins,and precipitated phases in the rolled alloy could impede the deformation at room temperature and increase the work hardening rate.After annealing,a decrease in the work hardening effect and an increase in the dynamic recovery effect were obtained due to the formation of fine equiaxed grains,and the increased volume fraction of precipitated phases,which significantly improved the elongation of the alloy.Additionally,the addition of Nd element could enhance the annealing recrystallization rate,reduce the Schmid factor difference between basal and prismatic slip systems,facilitate multi-system slip initiation and improve the alloy plasticity.

High density dislocations enhance creep ageing response and mechanical properties in 2195 alloy sheet

The creep strain of conventionally treated 2195 alloy is very low,increasing the difficulty of manufacturing Al-Cu-Li alloy sheet parts by creep age forming.Therefore,finding a solution to improve the creep formability of Al-Cu-Li alloy is vital.A thorough comparison of the effects of cryo-deformation and ambient temperature large pre-deformation(LPD)on the creep ageing response in the 2195 alloy sheet at 160℃with different stresses has been made.The evolution of dislocations and precipitates during creep ageing of LPD alloys are revealed by X-ray diffraction and transmission electron microscopy.High-quality 2195 alloy sheet largely pre-deformed by 80%without edge-cracking is obtained by cryo-rolling at liquid nitrogen temperature,while severe edge-cracking occurs during room temperature rolling.The creep formability and strength of the 2195 alloy are both enhanced by introducing pre-existing dislocations with a density over 1.4×10^(15)m^(−2).At 160℃and 150 MPa,creep strain and creep-aged strength generally increases by 4−6 times and 30−50 MPa in the LPD sample,respectively,compared to conventional T3 alloy counterpart.The elongation of creep-aged LPD sample is low but remains relevant for application.The high-density dislocations,though existing in the form of dislocation tangles,promote the formation of refined T1 precipitates with a uniform dispersion.

Interface analysis of 7B52 Al alloy laminated composite fabricated by hot-roll bonding

The bonding interface of 7B52 Al alloy laminated composite （ALC） fabricated by hot rolling was investigated using optical microscopy （OM）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, ultrasonic flaw detection （UFD）, and bonding strength tests. The results show that metallurgical bonding is achieved at the interface after composite rolling. The TEM analysis and tensile tests indicate that the 7B52 ALC plate combines high strength of the hard individual layer and good toughness of the soft individual layer. However, UFD technology and SEM analysis prove that the defects （thick oxide films, acid washed residues, air, oil and coarse particles） existing in the bonding interface are harmful to the bonding strength. To sum up, the composite roiling process is suitable for 7B52 ALC plate, and the content and size of the defects should be controlled strictly. Advanced surface treatment of each individual layer would be beneficial to further improve the bonding quality.

Microstructural development and its effects on mechanical properties of Al/Cu laminated composite

The microstructural development and its effect on the mechanical properties of Al/Cu laminated composite produced by asymmetrical roll bonding and annealing were studied. The composite characterizations were conducted by transmission electron microscope（TEM）, scanning electron microscope（SEM）, peeling tests and tensile tests. It is found that the ultra-fine grained laminated composites with tight bonding interface are prepared by the roll bonding technique. The annealing prompts the atomic diffusion in the interface between dissimilar matrixes, and even causes the formation of intermetallic compounds. The interfacial bonding strength increases to the maximum value owing to the interfacial solution strengthening at 300 °C annealing, but sharply decreases by the damage effect of intermetallic compounds at elevated temperatures. The composites obtain high tensile strength due to the Al crystallization grains and Cu twins at 300 °C. At 350 °C annealing, however, the composites get high elongation by the interfacial interlayer with submicron thickness.

Interfacial structure and mechanical properties of hot-roll bonded joints between titanium alloy and stainless steel using niobium interlayer

The hot-roll bonding was carried out in vacuum between titanium alloy and stainless steel using niobium interlayer. The interfacial structure and mechanical properties were analyzed. The results show that the plasticity of bonded joint is improved significantly. When the bonding temperature is 800 °C or 900 °C, there is not intermetallic layer at the interface between stainless steel and niobium. When the bonding temperature is 1000 °C or 1050 °C, Fe-Nb intermetallic layer forms at the interface. When the bonding temperature is 1050 °C, cracking occurs between stainless steel and intermetallic layer. The maximum strength of -417.5 MPa is obtained at the bonding temperature of 900 °C, the reduction of 25% and the rolling speed of 38 mm/s, and the tensile specimen fractures in the niobium interlayer with plastic fracture characteristics. When the hot-roll bonded transition joints were TIG welded with titanium alloy and stainless steel respectively, the tensile strength of the transition joints after TIG welding is -410.3 MPa, and the specimen fractures in the niobium interlayer.

Effect of heat treatment on microstructure and mechanical property of Ti-steel explosive-rolling clad plate

The effect of heat treatment on microstructure and mechanical properties of the Ti-steel explosive-rolling clad plate was elaborated by optical microscopy （OM）, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, micro-hardness test and shear test. The composites were subjected to heat treatment at temperature of 650-950 ~C for 60 min. The results show that the heat treatment process results in a great enhancement of diffusion and microstructural transformation. The shear strength decreases as the treatment temperature increases. Heated at 850 ℃ or below, their shear strength decreases slowly as a result of the formation of TiC in the diffusion interaction layer; while at the temperature of 850 ℃ or above, the shear strength decreases obviously, which is the consequence of a large amount of Ti-Fe intermetaUics （Fe2Ti/FeTi） along with some TiC distributing continuously at diffusion reaction layer.

LZ91合金在累积叠轧焊合过程中的界面焊合研究

采用金相显微镜和扫描电境观察了LZ91镁锂合金在累积叠轧焊(ARB)过程中的界面焊合现象。结果表明:道次压下量为50%的ARB工艺可以使LZ91板材获得良好的界面焊合,板材的抗拉强度和维氏硬度得到明显的改善。后续的ARB变形可以有效改善界面焊合质量,ARB轧制后退火可以使板材界面焊合强度增加。LZ91合金累积叠轧焊变形中的界面焊合机制是:合金表面硬化层先发生破裂,新鲜金属暴露,然后在轧制压力的作用下一起流动、相互接触,最终形成冶金结合。

Strength enhancement of Mg-3Gd-1Zn alloy by cold rolling

The severe cold rolling was employed to enhance strength of Mg-3Gd-lZn （mass fraction, %） alloy sheet. The 0.2% yield stress of the Mg-3Gd-1Zn hot-rolled sheet can be increased by 150% through the single-pass cold rolling with the reduction of 23%, due to the high intensity of dislocation and basal texture established during cold rolling. Compared with the Mg-3Gd-lZn hot-rolled sheet, the cold-rolled sheet annealed at 350 for 30 min may get an enhancement in strength without a great loss of ductility. The sheet processed by multi-pass cold rolling does not show a higher strength as expected, due to the softening effect of shear bands. However, the thin slab with the thickness less than 1 mm can be produced by the multi-pass cold rolling with the annealing treatment as few as possible.

Microstructure and properties of rare earth-containing Cu-Cr-Zr alloy

Cu-0.81Cr-0.12Zr-0.05La-0.05Y(mass fraction) alloy was successively subjected to hot rolling, solid solution treatment, cold rolling and aging treatments. Its microstructure, microhardness and electrical conductivity at different states were systematically investigated. The as-cast microstructure consists of three phases: Cu matrix, Cr and Cu5 Zr. Zr is completely dissolved into the matrix while partial Cr remains after the solid solution treatment. Aging of the cold-rolled sample makes nanocrystals of Cr and Cu5 Zr precipitate from the matrix, and the microhardness and electrical conductivity rise. A combination of high microhardness(HV 186) and high conductivity(81% IACS) can be obtained by aging the sample at 773 K for 60 min. As the aging temperature increases, the orientation degree of the Cu crystals gradually decreases to zero, but the microstrain in them cannot be eliminated completely owing to the presence of precipitates and dislocations. The Cr precipitates exhibit the N-W orientation relationship with the matrix when the coherence strengthening mechanism plays a main role.

Effect of stacking fault energy on mechanical properties of ultrafine-grain Cu and Cu-Al alloy processed by cold-rolling

Cu,Cu-2.2%Al and Cu-4.5%Al with stacking fault energies（SFE） of 78,35 and 7 mJ/m2 respectively were processed by cold-rolling（CR） at liquid nitrogen temperature（77 K） after hot-rolling.X-ray diffraction measurements indicate that a decrease in SFE leads to a decrease in crystallite size but increase in microstrain,dislocation and twin densities of the CR processed samples.Tensile tests at room temperature indicate that as the stacking fault energy decreases,the strength and ductility increase.The results indicate that decreasing stacking fault energy is an optimum method to improve the ductility without loss of strength.

Effects of cold rolling and heat treatment on microstructure and mechanical properties of AA 5052 aluminum alloy

The microstructures and mechanical properties of homogenized-rolled AA5052 aluminum alloys with different rolling reductions and following annealing treatments were investigated by optical microscope, scanning electron microscope, X-ray diffractometer, micro-hardness and tensile tests. The results show that with increasing rolling reduction, the equiaxed grains are elongated along the rolling direction obviously, and accumulation of rolling reduction increases the work hardening effect, which results in the enhanced strength and degraded plasticity. When rolling reduction is 87%, the ultimate tensile strength reaches 325 MPa but elongation is only 2.5%. There are much more secondary phase precipitates after annealing treatment. With an increase of annealing temperature, the amount of precipitates increases and work hardening diminishes continuously. The elongation is improved to ~23% but the tensile strength is decreased to 212 MPa after annealing at 300 °C for 4 h, which are comparable to those of as-homogenized alloy.

Microstructure and properties of Cu-2.3Fe-0.03P alloy during thermomechanical treatments

A short process without solution treatment was developed to manufacture Cu-2.3Fe-0.03 P alloy strips. After hot rolling-quenching and cold rolling with 80% reduction, the alloy exhibited excellent resistance to recrystallization softening. The hardness and electrical conductivity of Cu-Fe-P alloy under different thermomechanical treatments were measured by hardness tester and double bridge tester, respectively, and the microstructure of the alloy was examined by optical microscopy and transmission electron microscopy. The results show that the finished product of Cu-2.3Fe-0.03 P alloy was strengthened by work hardening, while the Fe precipitates with the size of about 25 nm stabilized the cold rolled structure. The conductivity decreased during cold rolling, especially for the pre-aged specimens, because the fine precipitates with the size smaller than 5 nm re-dissolved easily into the matrix. A Cu-Fe-P alloy with an electrical conductivity of 66% IACS and a hardness of HV 134 can be gained.

Prediction of edge cracks and plastic-damage analysis of Mg alloy sheet in rolling

A thermal-mechanical-damage coupled finite elements model was established to investigate temperature changes, edge cracks and rolling force during roiling of magnesium alloy sheet. A cuneal sheet was also adopted to study the influence of reduction on temperature, damage and rolling force. The results show that with increasing the reduction, the rolling force increases, and the temperature of the Mg sheet decreases. Edge cracks occur when the reduction is above 51.6%, with the damage value of above 0.49. The plastic-damage in Mg sheet rolling is a result of hole development, shearing deformation and accumulative plastic strain.

Microstructure of asymmetric twin-roll cast AZ31 magnesium alloy

The microstructural distribution along thickness of asymmetric twin-roll cast AZ31 magnesium alloy slab was investigated. It was found that the microstructure along the thickness of the slab was significantly inhomogeneous. There were many deformed bands with flow form near the upper surface of twin-roll cast plate. Very few deformed bands could be seen in the central part of the plate where the dendrites were thick. Fine dendritic structures dominated near the lower surface of the twin-roll cast strip. It is concluded that the shear strain caused by linear velocity difference between surfaces of upper and lower rolls results in the deformed bands of the twin-roll cast slab. Aluminum, zinc and manganese segregate to the boundary of dendrites, while silicon distributes inside the α-Mg solid solution.