Enhanced Strength in Cu-Ag-Zr Alloy by Combination of Cold Working and Aging

In this investigation, the effect of different degree of cold rolling and post-aging treatment on the microstructure and mechanical properties of a Cu-3wt.%Ag-0.5wt.%Zr alloy was studied by means of hardness measurement, tensile tests, optical and electron microscopy. The alloy was subjected to cold rolling up to 80% followed by aging in the temperature range of 400-500 °C. The yield strength, ultimate tensile strength and hardness were found to increase as degree of cold rolling increased, but at the expense of ductility. Aging of cold rolled samples in the studied temperature range has resulted in different combinations of strength and ductility. However, aging of cold rolled samples at 400 °C for 1 h has resulted in a combination of high strength and moderate ductility. A yield strength and ultimate tensile strength of 511 and 560 MPa, respectively with a ductility of 12% were achieved for 80% cold rolled and aged (400 °C for 1 h) sample. The high strength achieved after 80% cold rolling and aging is mainly attributed to precipitation of fine silver precipitates.     

Effect of ageing on microstructure and mechanical properties of bulk, cryorolled, and room temperature rolled Al 7075 alloy

The effect of ageing on mechanical properties and microstructural characteristics of a precipitation hardenable Al 7075 alloy subjected to rolling at liquid nitrogen temperature and room temperature are has been investigated in the present work employing hardness measurements, tensile test, XRD, DSC, and TEM. The solution-treated bulk Al 7075 alloy was subjected to cryorolling and room temperature rolling to refine grain structures and subsequently ageing treatment to simultaneously improve the strength and ductility. The solution treatment combined with cryorolling up to a true rolling strain of 2.3 followed by low temperature ageing at 100 °C for 45 h has been found to be the optimum processing condition to obtain fine grained microstructure with improved tensile strength (642 MPa) and good tensile ductility (9.5%) in the Al 7075 alloy. The combined effect of suppression of dynamic recovery, partial grain refinement, partial recovery, solid solution strengthening, dislocation hardening, and precipitation hardening are responsible for the significant improvement strength-ductility combination in the cryorolled Al 7075 alloy subjected to peak ageing treatment. The cryorolled and room temperature rolled Al 7075 alloy, upon subjecting to peak ageing treatment, have shown higher strength and ductility in the former than the latter. It is due to presence of high density of nanosized precipitates in the peak aged cryorolled sample.     

Tensile Behavior of Ultrafine-Grained Al-4Zn-2Mg Alloy Produced by Cryorolling

An Al-4Zn-2Mg alloy was subjected to cryorolling (CR) followed by short annealing. An average grain size of ~100 nm was achieved. Cryorolled samples showed large reduction in grain size due to suppression of dynamic recovery and absence of annihilation of dislocations, as compared to room temperature rolled samples. Further, the ultrafine-grained (UFG) Al-4Zn-2Mg alloy when subjected to natural aging showed an improved strength of ~413 MPa with ductility of ~25%, as compared to ~360 MPa and 22% ductility in peak aged condition of coarse-grained alloy. However, UFG alloy in peak aging condition, exhibited a relatively strength (~375 MPa) and 24% ductility combinations than the natural aging condition. The latter is attributed to dynamic precipitation and stored energy. In the present study, it is demonstrated that simultaneous improvement in strength as well as ductility can be achieved for the Al-4Zn-2Mg alloy through CR and controlled heat treatment combinations.     

固溶处理对7B04铝合金冷轧板组织性能的影响

在实验室中制备了试验用7B04铝合金,经铸造-均质化退火-热轧-中间退火-冷轧后制得7B04铝合金板材,并对合金板材进行了后续固溶时效处理,研究了固溶处理对其组织和性能的影响。结果表明,470 ℃×1 h固溶+120 ℃×21 h时效处理铝合金冷轧板材再结晶明显,有少量晶粒处于伸长状态,除粗大第二相粒子外,未发现细小第二相粒子,综合力学性能较好,抗拉强度为596 MPa,屈服强度为537 MPa,伸长率为14.88%。固溶温度达到480 ℃时,合金再结晶明显,但保温时间不能超过0.5 h,否则合金强度和塑性下降。     

Ga对6063铝合金力学性能及电阻率的影响

通过对不同Ga(镓)含量的6063铝合金进行对比试验,研究了微量杂质元素Ga对6063铝合金力学性能和导电性能的影响.研究表明,添加少量的Ga,对未经T6热处理的6063铝合金的力学性能影响不大,但对T6处理的6063铝合金,随着Ga含量的增加,合金的抗拉强度和塑性都有明显的提高.另外发现,随着Ga含量的增加,6063铝合金电阻率开始增加,但当w(Ga)＞0.04%,随着Ga含量的继续增加,电阻率下降.     

Study on the Mechanical Properties of Cast 6063 Al Alloy Using a Mixture of Aluminum Dross and Green Sand as Mold

The mechanical characteristics of 6063 aluminum alloy cast in a mixture of aluminum dross and silica sand as mold have been examined. The amount of dross in the green silica sand was varied in the range of 0?C80% with bentonite as binder. In all, 40 samples were cast, and 8 of these were left in the as-cast condition for control while 32 were first homogenized at 470°C for 6?h and then rolled in a two-high mill at ambient temperature to 10% reduction in one pass. The rolled samples were solution heat treated at 515°C for 8?h followed by normalizing, annealing, and quench tempering, respectively. The samples were then simulated and tensile behavior coupled with the evaluation of microhardness and microstructures developed. The results obtained demonstrate significant improvement in mechanical properties from 50% to 80% dross in the mold. Tensile strength increased to 177?MPa and 15% elongation compared with conventional 6063-T5 aluminum alloy with 145?MPa tensile strength and 8% elongation. The improvement in mechanical properties by the quench-tempered samples can be attributed to the inducement of fine and coherent Mg₂Si crystals within the matrix. Furthermore, the overall analysis of the proportion of dross to the size of cast show that about 64% of dross generated can be utilized as mold material.     

Effect of large cold deformation after solution treatment on precipitation characteristic and deformation strengthening of 2024 and 7A04 aluminum alloys

1Introduction Studies on thermomechanical treatment of aluminum alloy can date from the1960s[1,2].A great deal of achievements concerning this study has been obtained after near40years of development[3?7].Among them,the achievement of intermediate thermom…     

强变形工艺对2519A铝合金组织与性能的影响

通过硬度测试、拉伸性能测试、透射电镜观察等分析手段研究了不同强变形工艺下2519A铝合金的力学性能与微观组织。结果表明,经50%的冷轧变形和165 ℃人工时效后,2519A合金的力学性能明显提高,其抗拉强度、屈服强度和伸长率分别为522 MPa、468 MPa和8.5%。而在冷变形前添加165 ℃×2 h预时效处理,合金的力学性能进一步提高,其抗拉强度、屈服强度和伸长率分别达到535 MPa、497 MPa和8%。预时效处理可以提高合金中θ′相的密度,使析出相分布更加均匀,有助于提高合金的力学性能。     

阳极氧化对超声波焊接6063铝合金与PPS的影响

为实现铝合金与塑料的有效连接,采用磷酸阳极氧化工艺对6063铝合金表面进行预处理,使用超声波金属焊接机对6063铝合金与聚苯硫醚(PPS)进行焊接.结果 表明:未经处理的6063铝合金与PPS超声波焊接接头抗剪强度随着焊接时间、焊接压力的增加先增大后减小,当焊接压力和焊接时间分别为0.5 MPa和6s时,可获得最大抗剪...     

加工工艺对高性能铜合金组织和性能的影响

在真空感应炉熔炼得到Cu-0.2Cr-0.1Ag合金,研究了该合金在不同加工条件下的组织、强度和导电性变化.研究表明,通过固溶强化、时效强化和形变强化等手段的配合,可以获得高强度、高导电性的Cu-0.2Cr-0.1Ag合金.固溶、时效处理后的合金导电率达91%IACS,伸长率为37.4%.在固溶后加入冷变形,然后再时效,可以使强度提高84 MPa,而导电率不发生变化,再继续冷变形可以使强度提高到556 MPa.     

Effect of aging and cold rolling on the microstructure and mechanical properties of a new Fe-Mn-Al-Cr-C duplex alloy

The microstructural changes that occur during aging and cold rolling of a new Fe-Mn-Al-Cr-C duplex alloy have been investigated. Two treatments were developed to produce either a good combination of tensile strength and ductility (σ _u =800 MPa, σ _y =525 MPa, and A=46%) or a high strength (σ _u =1340 MPa, σ _y =1200 MPa, and A=15%) with a ductile type of fracture after aging at 320 °C. Aging between 550 °C and 700 °C led to a significant decrease in strength and ductility due to the precipitation of the brittle βMn phase. However, aging above 750 °C showed a considerable increase in strength and ductility due to the precipitation of very fine grains of ferrite within the austenite phase.     

Solid-state recycling of aluminium alloy swarf through cold profile extrusion and cold rolling

In this study, the possibility of solid-state recycling of aluminium alloy machining swarf using cold extrusion and a subsequent cold rolling process is investigated. Cast Al-Si alloy swarf was cold compacted into billets and successfully profile-extruded into square bars with a rectangular cross-sectional aspect ratio of 1:1.8 under an extrusion ratio of 4 or more. After annealing, the extruded bars underwent multi-pass cold rolling into 1-mm thick strips with a total rolling reduction of 85%. Optical microscopy demonstrated that in material recycled using only an extrusion process, coarse residual voids existed in regions where insufficient plastic strain was introduced, causing a visible expansion of the material during heat treatment. However, uniaxial tensile tests showed that extrusion-recycled material had a higher mechanical strength than the original aluminium alloy, implying sufficient bonding among the individual pieces of machining swarf. It was also found that the strength and density of material recycled through extrusion and an additional rolling process were superior to material recycled using extrusion only. Moreover, it was observed that the ductility of the recycled materials was inferior to that of the original aluminium alloy.     

扩散焊工艺对6063铝合金焊接接头性能的影响

分别采用固相扩散焊和瞬间液相扩散焊方法焊接6063铝合金。采用金相显微镜对扩散界面附近的显微组织进行了分析;采用万能试验机测试了焊接接头的抗拉强度。试验结果表明,在连接同种铝合金材料的情况下,固相扩散焊相比瞬间液相扩散焊能够获得更为良好的接头性能。在焊接温度540℃、焊接压力8 MPa、保温时间80 min时,固相扩散焊接头区域成分均匀,没有空洞等缺陷,抗拉强度为122 MPa,达到同种热处理条件下母材抗拉强度(130 MPa)的94%。     

Thermomechanical treatment of austempered ductile iron

The production of lightweight ferrous castings with increased strength properties became unavoidable hter aluminum and magnesium castings. The relatively new ferrous casting alloy ADI offers promising strength prospects, and the thermo-mechanical treatment of ductile iron may suggest a new fluence of thermomechanical treatment,either by ausforming just after quenching and before the onset of austempering reaction or by cold rolling after of this work, ausforming of ADI up to 25％ reduction in height during a rolling operation was found to add a mechanical processing component compared to the conventional ADI heat treatment, thus increasing the rate ics of ausferrite formation was studied using both metallographic as well as XRD-techniques. The effect of ausforming on strength was quite dramatic (up to 70％ and 50％ increase in the yield and ultimate strength respectively). A mechanism involving both a refined microstructural scale and an elevated dislocation density was suggested. Nickel eformation is necessary to alleviate the deleterious effect of alloy segregation on ductility.luence of cold rolling (CR) on the mechanical properties and structural characteristics ofADI wasinvestigated. The variation in properties was related to the amount of retained austenite nsformation. In the course of tensile deformation of ADI, transformation induced plasticity (TRIP) takes place, indicated by the increase of the instantaneous value of strain-hardening exponent with o partial transformation of γr to martensite under the CR strain. Such strain-induced transformation resulted in higher amounts of mechanically generated therefore increased, while ductility and impact toughness decreased with increasing CR reduction.     

Effect of Cold Rolling and Heat Treatment on Microstructure and Mechanical Properties of Ti-4Al-1Mn Titanium Alloy

Mechanical behavior of Ti-4Al-1Mn titanium alloy has been studied in annealed, cold-rolled and heat-treated conditions. Room temperature tensile strength as well as % elongation has been found to be low with increasing amount of cold rolling. Lowering of strength in cold worked condition is attributed to premature failure. However, the same has been mitigated after heat treatment. Significant effect of cooling media (air and water) from heat treatment temperature on microstructure was not found except for the degree of fineness of α plates. Optimum properties (strength as well as ductility) were exhibited by samples subjected to 15% cold rolling and heat treatment below β transus temperature, which can be attributed to presence of recrystallized microstructure. In cold worked condition, the microstructure shows fine fragmented α plates/Widmanstätten morphology with high dislocation density along with a large amount of strain fields and twinning, which gets transformed to recrystallized equiaxed microstructure and with plate-like morphology after near β heat treatment. Prior cold work is found to have a significant effect on mechanical properties supported by evolution of microstructure. Twinning is found to be assisting in deformation as well as in recrystallization through the formation of deformation and annealing twins during cold working and heat treatment. Fracture analysis of the tested sample with prior cold work and heat-treated condition revealed quasi-ductile failure as compared to only ductile failure features seen for samples heat treated without prior cold work.     

不完全再结晶Fe40Mn10Cr25Ni25高熵合金的室温及低温力学性能

采用冷轧和退火热处理工艺制备了不完全再结晶结构的Fe₄₀Mn₁₀Cr₂₅Ni₂₅高熵合金,分析了合金的室温(298 K)及低温(77 K)拉伸时的力学性能。结果表明,合金具有优良的室温及低温力学性能,合金在低温拉伸时强度和塑性均得到了提高,其室温强度和断后伸长率分别为880 MPa和18%,低温强度和断后伸长率分别为1360 MPa和36%。合金在室温变形以位错滑移为主,低温变形以位错滑移和孪生为主。室温拉伸时,粗晶晶粒先于细晶晶粒变形,导致试样内部产生了应变梯度,提高了合金的加工硬化率,使合金在室温下具有良好的强塑性。低温拉伸时,粗晶晶粒中形成了大量的变形孪晶,从而提高了合金的低温力学性能。     

High strength and ductile ultrafine-grained Cu–Ag alloy through bimodal grain size,dislocation density and solute distribution

Ultrafine-grained materials produced by different severe plastic deformation methods show very high strengths but their tensile ductility is often very low. In the present work, we demonstrate an approach for retaining high strength while recovering ductility in a Cu–3 at.% Ag alloy through cold rolling and short-time annealing. X-ray line profile analysis of cold-rolled and annealed samples reveals the development of a heterogeneous solute atom distribution due to the dissolution of nanosized Ag particles in some regions of the matrix. In regions with higher solute (Ag) content, the high dislocation density present following rolling is stabilized, while in other volumes the dislocation density is decreased. High-resolution scanning electron microscopy confirms the presence of regions of varying Ag content in the matrix. Microstructure analysis of the rolled and annealed samples revealed bimodal grain size, dislocation density and solute Ag distributions as well as nanosized Ag precipitation. The as-rolled samples exhibit high tensile strengths of ～600–700 MPa with negligible uniform elongation (～1%). After short-time annealing the strength decreases only slightly to ～550–620 MPa with significant improvement in uniform elongation (from 1 to 10%); this is mainly attributed to the bimodal microstructure.     

Effect of Heat Treatment Parameters on the Microstructure and Properties of Inconel-625 Superalloy

Inconel-625 is a solid solution-strengthened alloy used for long-duration applications at high temperatures and moderate stresses. Different heat treatment cycles (temperatures of 625-1025 °C and time of 2-6 h) have been studied to obtain optimum mechanical properties suitable for a specific application. It has been observed that room temperature strength and, hardness decreased and ductility increased with increase in heat treatment temperature. The rate of change of these properties is found to be moderate for the samples heat-treated up to 850 °C, and thereafter, it increases rapidly. It is attributed to the microstructural changes like dissolution of carbides, recrystallization and grain growth. Microstructures are found to be predominantly single-phase austenitic with the presence of fine alloy carbides. The presence of twins is observed in samples heat-treated at lower temperature, which act as nucleation sites for recrystallization at 775 °C. Beyond 850 °C, the role of carbides present in the matrix is subsided by the coarsening of recrystallized grains and finally at 1025 °C, significant dissolution of carbide results in substantial reduction in strength and increase in ductility. Elongation to an extent of >71% has been obtained in sample heat-treated at 1025 °C indicating excellent tendency for cold workability. Failure of heat-treated specimens is found to be mainly due to carbide particle-matrix decohesion which acts as locations for crack initiation.     

部分再结晶对NiFeCoCrMn高熵合金显微组织和拉伸性能的影响

为了调控NiFeCoCrMn高熵合金强度和塑性之间的平衡关系,采用传统的热力学加工技术(冷轧和再结晶),通过不同的再结晶退火工艺得到不同程度的位错强化,并对具有不同再结晶比例的合金进行拉伸性能测试.随着再结晶比例的增加,即应变硬化程度的下降,合金的均匀伸长率和加工硬化率显著提高,但屈服强度和抗拉强度降低.尤其在650℃...     

多向强应变及时效处理对铝合金的强韧性影响

利用多向锻造及时效处理技术加工变形铝合金,使铝合具有高强度和良好的塑性.研究结果表明,试样组织显著细化且超细的第二相微粒弥散分布,抗拉强度和硬度大幅度增加且塑性良好,抗拉强度和伸长率分别为396.3 MPa和11.08％.锻件强度和硬度大幅度提高是由于组织显著细化且超细的第二相微粒弥散分布;多次累积应变和时效处理改善晶界状态,使锻件的塑性增强.