温形变工艺对30Mn2V非调质钢显微组织的影响

研究了 3 0 Mn2 V钢在 70 0～ 80 0℃范围内平面应变压缩变形时组织的变化规律。结果表明 ,在合适的温形变工艺条件下 ,可诱导铁素体析出 ,显著细化铁素体晶粒 。

中温形变对0Cr16Ni16钢组织和性能的影响

以低温形变和高温形变工艺强化机理为基础,根据合金化原则拟定出中温形变强化工艺模型;编制0Cr16Ni16中温形变的强化工艺并进行拉伸试验和金相试验,结果为:奥氏体中析出复合碳化物可使0Cr16Ni16强度超过680MPa。

中温形变对45钢石墨化的影响

实验采用中温形变处理方式,研究温度、形变量和保温时间对45钢短棒状渗碳体转变的影响,探究在较低温度条件下(650～750℃)形变过程对其石墨化的影响。利用光学显微镜、扫描电镜、维氏硬度计及拉曼光谱仪等手段对形变后45钢进行显微组织和力学性能分析。结果表明:增加形变量、形变温度和保温时间均有利于短棒状渗碳体向粒状转变,使硬度有所降低;在大形变量条件下形变温度升高至两相区温度,45钢中有石墨析出。

中温形变热处理对新型镍基高温合金组织和力学行为的影响

采用EBSD、SEM和准静态室温单轴拉伸试验研究了不同中温形变热处理工艺与新型镍基高温合金微观组织和室温力学性能之间的关系。结果表明,新型镍基高温合金经中温形变热处理后可明显提高退火孪晶的长度分数,最高可达40.6%。退火孪晶的形成主要以晶粒的“生长意外”机制为主。同时,相比于固溶+双级时效处理试样的力学性能(屈服强度σy=1018MPa,延伸率εf=17.44%),合金在750℃轧制变形30%后在1120℃退火30min并经双级时效处理,其σy可提高499 MPa,为1517 MPa,而其εf仅降低了4.69%。在750℃轧制变形50%后在1120℃退火30 min并经双级时效处理,其σy可提高352 MPa,为1370 MPa,而其εf基本保持不变。这种强度的升高主要归因于晶粒细化和退火孪晶的共同作用,这为高性能镍基高温合金提供一种新的强化策略。

中温形变对45钢组织及力学性能的影响

采用中温形变处理方式,从温度、形变量和保温时间3个方面,探究A_1线附近形变过程对热轧态45钢中片层渗碳体的影响。结果表明:增加形变量、形变温度和保温时间均有利于片层状渗碳体向粒状转变,可起到球化退火效果。在大形变量及一定保温时间下,粒状渗碳体尺寸和分布均匀且伴随着铁素体动态再结晶过程。而在大形变量且形变温度升高至A_1线以上条件下,在动态再结晶铁素体基体上析出细小弥散分布的渗碳体颗粒会形成复合组织(α+θ),使试样硬度明显增加至190 HV0.1。

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.

一种低碳低合金超高强度钢丝低周疲劳寿命的研究

采用恒应变幅（△ε）控制低周疲劳试验方法，测定了一种低碳低合金超高强度钢丝的循环应力幅（△σ）和最大应力（σ_（ｍａｘ））与循环周次（Ｎ）之间的关系，并与高碳高强度Ｐａｔｅｎｔｉｎｇ钢丝对比。研究了温形变处理对钢丝低周疲劳性能的影响。结果得出，低碳低合金钢丝比高碳Ｐａｔｅｎｔｉｎｇ钢丝具有高的低周疲劳抗力，温形变处理又可提高低周疲劳寿命３０％～３５％。并对这种钢丝的低周疲劳损伤进行了评价。

(F+M)双相15钢的组织与性能

研究了 15钢在不同热处理条件下的显微组织和拉伸性能。结果表明 ,发展岛状 (F +M)双相组织和纤维 (F+M)双相组织是提高 15钢强塑性的有效途径。探讨了亚温淬火与亚温形变淬火的最佳工艺 。

Mechanical properties of Mg-6Gd-1Y-0.5Zr alloy processed by low temperature thermo-mechanical treatment

An as-solution treated Mg-6Gd-1Y-0.4Zr alloy was processed by low temperature thermo-mechanical treatments （LT-TMT）, including cold tension with various strains followed by aging at 200 °C to peak hardness. The results show that the precipitation kinetics of the alloy experienced LT-TMT is greatly accelerated and the aging time to peak hardness is greatly decreased with increasing tensile strain. The tensile yield strength, ultimate tensile strength and elongation at room temperature of the alloy after cold tension with strain of 10% and peak aging at 200 °C are 251 MPa, 296 MPa and 8%, respectively, which are superior to the commercial heat-resistant WE54 alloy, although the latter has a higher rare earth element content.

Effects of high temperature pre-straining on natural aging and bake hardening response of Al-Mg-Si alloys

The influences of high temperature pre-straining (HT-PS) on the natural aging and bake hardening of Al?Mg?Si alloys were investigated by Vickers microhardness measurements, differential scanning calorimetry (DSC) analysis and transmission electron microscopy (TEM) characterization. The results show that pre-straining at 170 °C immediately after quenching can effectively resolve the rather high T4 temper hardness caused by the conventional room temperature (RT) pre-straining treatment, and give a better bake hardening response (BHR) after paint-bake cycle. HT-PS 7% at 170 °C for 10 min is chosen as the optimum process as it provides lower T4 temper hardness and better BHR. The simultaneous introduction of dislocations and Cluster (2) can significantly suppress the natural aging and promote the precipitation of β″ phase, and reduce the effects of deformation hardening by dynamic recovery.

High temperature deformation behavior and optimization of hot compression process parameters in TC11 titanium alloy with coarse lamellar original microstructure

The high temperature deformation behaviors of α＋β type titanium alloy TC11 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si） with coarse lamellar starting microstructure were investigated based on the hot compression tests in the temperature range of 950-1100 ℃ and the strain rate range of 0.001-10 s-1. The processing maps at different strains were then constructed based on the dynamic materials model, and the hot compression process parameters and deformation mechanism were optimized and analyzed, respectively. The results show that the processing maps exhibit two domains with a high efficiency of power dissipation and a flow instability domain with a less efficiency of power dissipation. The types of domains were characterized by convergence and divergence of the efficiency of power dissipation, respectively. The convergent domain in a＋fl phase field is at the temperature of 950-990 ℃ and the strain rate of 0.001-0.01 s^-1, which correspond to a better hot compression process window of α＋β phase field. The peak of efficiency of power dissipation in α＋β phase field is at 950 ℃ and 0.001 s 1, which correspond to the best hot compression process parameters of α＋β phase field. The convergent domain in β phase field is at the temperature of 1020-1080 ℃ and the strain rate of 0.001-0.1 s^-l, which correspond to a better hot compression process window of β phase field. The peak of efficiency of power dissipation in ℃ phase field occurs at 1050 ℃ over the strain rates from 0.001 s^-1 to 0.01 s^-1, which correspond to the best hot compression process parameters of ,8 phase field. The divergence domain occurs at the strain rates above 0.5 s^-1 and in all the tested temperature range, which correspond to flow instability that is manifested as flow localization and indicated by the flow softening phenomenon in stress-- strain curves. The deformation mechanisms of the optimized hot compression process windows in a＋β and β phase fields are identified to be spheroidizing and dynamic recrystallizing controlled by self-diffusion mechanism, respectively. The microstructure observation of the deformed specimens in different domains matches very well with the optimized results.

Effect of deformation temperature on microstructure and mechanical properties of 7055 aluminum alloy after heat treatment

The multi-pass hot compression test of 7055 aluminum alloy was performed at different temperatures and then the samples were heat treated by T6 heat treatment.The compressed samples were analyzed by OM and TEM.The results reveal that the average aspect ratio of the grains in the specimens compressed first decreases and then increases,the dislocation density decreases and subgrain diameter increases with the increase of deformation temperature.The effects of deformation temperature on the microstructure and mechanical properties of 7055 aluminum alloy after heat treatment were investigated by means of OM and mechanical property test.The results indicate that the deformation temperature significantly influences microstructure and mechanical property of 7055 aluminum alloy.The volume fraction of recrystallization grains presents a ＂fall-rise＂ pattern with the deformation temperature rising.The mechanical properties get better when the volume fraction of recrystallization grains decreases.Moreover,the volume fraction of recrystallization grain has a minimum value,appropriately 45%,and the sample exhibits the highest strength and elongation at the deformation temperature of 400 ℃.

Properties and microstructure of Ti6Al4V by deformation accelerated low temperature plasma nitriding

An integrated low-temperature nitriding process was carried out for Ti6Al4V to investigateitseffect on microstructure and properties.The process was designed to enhance the nitriding kinetics in low-temperature（500℃） nitriding by deformation, and to strengthen Ti6Al4V alloybydispersionat the same time. Specimens of Ti6Al4V alloyweretreated through the process of solid solutionstrengthening-cold deformation-nitriding at 500℃. The white nitriding layeris formed after some time and then kept stable, changing little withthedeformationdegreeand time. The effect of aging on substrate is significant. Surface hardness and substrate hardnessincrease with deformation increasing. The construction was investigated by XRD.The surface nitridesare TiN, Ti2N, Ti4N3-Xand Ti3N1.29,and thenitridesin cross-section are Ti3N1.29and TiN0.3. The wear tests of specimens after nitriding, aging and deformation were carried out,andthetest data show that the nitrided pieces have the best wear resistance.

Microstructure evolution of Zn-8Cu-0.3Ti alloy during hot deformation

The hot deformation behavior of homogenized zinc alloy was investigated through uniaxial compression test on a Gleeble-1500 thermal-mechanical simulator within a temperature range of 230-380°C and a strain rate range of 0.01-10 s -1 ,the corresponding flow curves and their characters were determined and analyzed,and microstructures were studied by optical,SEM and TEM microscopy.The results indicated that the microstructure evolution of zinc alloy during hot deformation involves the spheroidization of the phase of TiZn15,coarsening of the precipitated phase and dynamic recrystallization（DRX）of the phase of matrix,leading to the formation of the polyphase（η＋ε＋TiZn15）structure.The spheroidization of the phase of TiZn15 during hot deformation was beneficial to the particle nucleation stimulated and then promoted to DRX of matrix.The dynamic recrystallization grain size of the matrix phase decreased firstly and then increased with elevating the temperature,and the degree of DRX became more complete when the strain rate and strain became larger.Hot deformation accelerated the diffusion of Cu atom,which resulted in the coarsening of the precipitated phase.Thus,the microstructure was refined owing to the pinning effect of the precipitated phase.

Flow instability criteria in processing map of superalloy GH79

Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester.Based on the deformation behavior and microstructural evolution of superalloy GH79,different types of instability criteria of PRASAD,GEGEL,MALAS,MURTY and SEMIATIN were compared,and the physical significance of parameters was analyzed.Meanwhile,the processing maps with different instability criteria were obtained.It is shown that instability did not occur when average power dissipation rate was larger than 60%in the temperature range of 900-930°C and 960-1080°C,corresponding to the strain rate range of 5×10 -4 -1.8×10 -1 s -1 and 5×10 -4 -1.5×10 -1 s -1 ,respectively.The two domains are appropriate for the processing deformation of superalloy GH79.

Microstructural evolution and mechanical properties of TIG welded superalloy GH625

The tungsten inert gas welding（TIG） technique was employed to weld the nickel-based wrought superalloy GH625, and the microstructures, element distribution, grain boundary character and mechanical properties of the welded joint were investigated systematically. The results indicated that the welded seam was of austenite dendrite crystal structure and no obvious heat affected zone（HAZ） was observed. A number of precipitated δ phases with homogeneous distribution were observed in the interdendritic region of the weld fusion zone. The abnormal phenomenon observed in the weld fusion zone of GH625, i.e., higher hardness and larger grain size compared with the base metal, may be attributed to the precipitated δ phase in the weld fusion zone. The higher tensile strength in the base metal was mainly attributed to the presence of more contents of fine grains and twin boundaries, while the lower elongation in the welded joint was mainly owing to the precipitated δ phase.

Ni_(56)Mn_(25-x)Cr_xGa_(19)(x=0,2,4,6) high temperature shape memory alloys

The microstructure,martensitic transformation behavior,mechanical and shape memory properties of Ni56Mn25-xCrxGa19（x=0,2,4,6） alloys were investigated.Single phase of martensite with tetragonal structure is present for x=0,and dual-phase containing martensite and γ phase is observed for x≥2.The martensitic transformation peak temperatures decrease monotonically from 401 ℃ for x=0 to 197 ℃ for x=6.The introduction of γ phase by Cr addition is proved to be effective in improving the workability and ductility.The tensile stress and strain are 497 MPa and 8 % for x=4,and 454 MPa and 5.5 % for x=6,respectively.The shape memory strain values are 2.7 % under a residual strain of 4.5 % for x=4,and 1.9 % under a residual strain of 3.5 % for x=6,respectively.

GH4169高温合金的热加工工艺

通过调整工艺参数,结合力学性能和微观组织分析,研究了GH4169高温合金的热加工工艺。结果表明,均质化工艺可改善强化元素在枝晶间的偏析;开坯锻造的锻造比≥3时可改善混晶;采用中温形变热处理工艺可明显提高GH4169高温合金的力学性能,(1130~1160)℃开坯锻造+(980~1020)℃中温轧制热处理(水冷)+直接时效可提高合金的力学性能,抗拉强度可达1350 MPa,硬度可达50 HRC。

Strain rate-dependent high temperature compressive deformation characteristics of ultrafine-grained pure aluminum produced by ECAP

To explore the effect of strain rate ε on the high temperature deformation characteristics of ultrafine-grained materials, the deformation and damage features as well as microstructures of ECAP-treated pure Al at different temperatures T and strain ratesε were systematically studied through compression tests and microscopic observations. The increase in ε eliminates strain softening at T≤473 K, and largely enhances the yield strength and flow stress at 473?573 K. The shear deformation dominates the plastic deformation of ECAP-treated Al. Many cracks along shear bands (SBs) are formed at T≥473 K and secondary SBs basically disappear at 1×10?3 s?1; however, at 1×10?2 s?1, cracks are only observed at temperature below 473 K, and secondary SBs become clearer at T≥473 K. The microstructures of ECAP-treated Al mainly consist of sub-grains (SGs). The increase in ε inhibits the SG growth, thus leading to the increases both in yield strength and flow stress at high temperatures.

Hot deformation behavior and microstructure evolution of 1460 Al-Li alloy

The hot deformation behavior and microstructure evolution of 1460 Al-Li alloy were investigated by isothermal compression test conducted at various strain rates（10-3-10 s-1） and temperatures（573-773 K）. The flow stress curves were corrected by considering the friction at the platen/specimen interface and the temperature change due to the deformation heating. The effects of strain, strain rate and temperature on the deformation behavior were characterized by the Zener-Hollomon parameter in a hyperbolic-sine equation, and the constitutive equations were established according to the peak flow stress associated with dynamic recovery, dynamic recrystallization and the dissolution of T1 phases. In the entire strain rate and temperature range, the prediction capabilities of the developed constitutive equation are proved to be feasible and effective with a linear correlation coefficient and an average absolute relative error coefficient of 0.9909 and 6.72%, respectively.