强变形诱导析出相回溶后的Al-Cu合金再时效行为

采用透射电镜观察与分析,探讨含析出相的Al-Cu合金经多向压缩变形诱导析出相回溶后形成的过饱和固溶体的再时效行为。研究结果表明:Al-Cu合金由强塑性变形诱导析出相回溶形成的过饱和固溶体,在变形停止后再时效时显著加速时效析出过程;析出相的析出顺序与加热温度、变形量及变形后的晶粒尺寸有关;若加热温度足够消除强变形产生的高应力,则析出顺序为过渡相→稳定相;若加热温度不能消除变形产生的高应力,且晶粒超细化,则再析出时过渡相被抑制,直接生成稳定相。     

控轧控冷工艺对X120管线钢碳氮化物析出的影响

采用不同的控轧控冷工艺研究了未再结晶区变形量、冷却速度和终冷温度等轧制工艺参数对X120管线钢碳氮化物析出的影响,并根据Orowan机制对析出相强度贡献量进行了理论估算.结果表明:轧制工艺的变化对析出相的类型与相结构没有影响;提高未再结晶区变形量主要可促进铌的析出,并有利于提高X120管线钢的屈服强度;冷却速度和终冷温度对X120管线钢碳氮化物析出的影响较小.     

302HQA钢冷变形过程组织演化分析

通过室温压缩实验,研究了奥氏体不锈钢302HQA的冷变形行为.组织分析和X射线衍射分析表明,冷变形过程产生了形变马氏体.进一步磁性检测表明:随着变形量的增加,形变马氏体的量也增加;在小变形条件下,变形速率对形变马氏体的生成量影响较小;当变形量增加到50%时,随着变形速率的增加,由于变形热效应的影响,形变马氏体含量反而有所下降.     

形变时效工艺对低铍Cu-Ni-Be合金力学性能和电导率的影响

运用正交设计研究形变时效工艺(冷变形量、时效温度和时效时间)对低铍含量Cu-Ni-Be合金力学性能和电导率的影响,并通过光学显微镜、扫描电镜和透射电镜对其显微组织进行分析。研究结果表明:在形变时效处理的3个主要工艺参数中,时效时间对抗拉强度、屈服强度和相对电导率的影响最大,时效温度次之,冷变形量最小;合金在经过37.5%冷变形的轧制后,在470℃时效2h,γ″析出物细小且弥散分布在基体中,合金具有较好的综合性能。     

镍基合金粉末的预变形与热处理

对镍基合金粉末进行了20%,40%,60%的预变形,并对不同变形量的粉末在1050℃,1100℃,1120℃温度下保温2h热处理.结果表明:在1050℃,形变量增至60%时,发生完全再结晶且组织均匀化程度显著增加;1 100℃时,显微组织基本上都已均匀,基体中沿再结晶晶粒的晶界均匀析出弥散分布的γ′相;1 120℃时,显微组织更为均匀,在晶界上析出粗大γ′相.     

17-4PH不镑钢的研究现状及发展趋势

阐述了当前核工业螺栓中应用广泛的沉淀硬化17-4PH不锈钢的成分,合金元素在析出强化过程中的作用及热处理工艺对其综合性能的影响,归纳总结了时效完成后该钢的显微组织形貌对力学性能影响.研究表明：时效过程中富铜相的析出是17-4PH不锈钢的主要强化机制.未来发展趋势在于渗氮表面强化热处理工艺的广泛应用,该工艺是当前行业上最为认同的一项工艺;而使用三维原子探针作为表征手段对富铜相析出进行纳米级别分析是未来研究的一种新思路.     

17-4PH不锈钢的研究现状及发展趋势

阐述了当前核工业螺栓中应用广泛的沉淀硬化17-4PH不锈钢的成分,合金元素在析出强化过程中的作用及热处理工艺对其综合性能的影响,归纳总结了时效完成后该钢的显微组织形貌对力学性能影响.研究表明:时效过程中富铜相的析出是17-4PH不锈钢的主要强化机制.未来发展趋势在于渗氮表面强化热处理工艺的广泛应用,该工艺是当前行业上最为认同的一项工艺;而使用三维原子探针作为表征手段对富铜相析出进行纳米级别分析是未来研究的一种新思路.     

超纯铁素体不锈钢热变形过程中的析出行为

利用热力模拟实验机及试验轧机研究了添加Ti,V的超纯中铬铁素体不锈钢热变形过程中的析出行为变化特点,并采用热动力学计算及透射电子显微镜观察来表征析出相特征.结果表明:热变形过程中形成的析出相主要为TiC,这与热动力学分析一致.这些析出相的特征与变形温度密切相关,随着变形温度的降低,析出相TiC尺寸更加细小且分布更加弥散.这主要是由于变形温度降低时扩散速率相对较低,不利于析出相长大,而晶体缺陷增加,形变诱导析出的有效形核位置增加.这一热变形过程中的析出行为变化规律在中试试验条件下得到了验证.     

时效对Cu-Cr-Zr合金显微硬度及导电率的影响

探讨了时效工艺及形变量对Cu 0 .3Cr 0 .15Zr合金显微硬度及导电率的影响。结果表明 ,合金经 92 0℃固溶处理后在 4 2 0℃及 4 6 0℃时效可分别达到较好的硬度和导电率 ,分别达 183HV和 6 8%IACS ;时效前对合金加以适当冷变形可加速合金时效析出过程。影响合金导电率的主要因素是基体中固溶元素的含量 ,含量越高 ,导电率越低 ,反之则越高。而时效前冷变形可以增加合金内部位错等缺陷的数量 ,加速了合金第二相的析出。     

铸造共晶铝硅合金中析出相对断裂行为的影响

通过对铸造共晶Al-Si合金断口及析出相的分析研究了拉伸过程中基体内析出相的断裂特点.结果发现：拉伸过程中基体内初、共晶硅以穿晶断裂为主,这与颗粒内部存在的结构缺陷有关;直径小于2.0μm的初晶硅能够抑制二次裂纹的扩展.块状富铁相表现出穿晶断裂特点,鱼骨状富铁相中的微裂纹沿一次枝晶轴向生长.富铜相对裂纹扩展具有强烈地偏折作用;以富铁相为核心析出的富铜相能抑制富铁相中微裂纹的形成.提高合金中Cu含量可以降低富铁相的有害作用,改善合金的力学性能.     

Influence of deformation on precipitation in AZ80 magnesium alloy

Precipitates in the conventionally processed (solution treatment followed by aging) AZ80 alloy are coarse, cellular, and incoherent. They nucleate and grow on the basal planes of the matrix or distribute discontinuously in the alloy. Their unique morphology and undesired distribution make them ineffective for precipitation strengthening. This condition, however, can be modified by applying selected deformation and heat treatment conditions. The effect of deformation and heat treatment on the morphology and distribution of precipitates has been studied. Deformation was introduced by hot extrusion, cold rolling, or equal channel angular pressing (ECAP). The microstructures were characterized using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results showed that cold deformation improved precipitation more significantly than hot deformation, and twinning promoted precipitation more effectively than slip. When ECAP was applied, the Bc-route induced more precipitates than the A-route.     

时效前冷变形对Cu-3.0Ni-0.64Si合金性能的影响研究

探讨了时效前冷变形对Cu-3.0Ni-0.64Si合金抗拉强度及导电率的影响规律,并分析了时效后合金的显微组织。结果表明,Cu-3.0Ni-0.64Si合金时效前最佳冷变形量为80%,经过时效处理温度480℃,保温时间3.5 h后,合金电导率最高达到50.8%IACS,抗拉强度达到603.18 MPa。     

2205双相不锈钢中σ相的析出规律

2205双相不锈钢经过1300℃固溶处理和不同程度的冷轧变形后,在不同温度下保温不同时间后水冷.利用金相显微镜和透射电镜观察试样的组织,用 Image Tool 软件分析组织中σ相的含量,研究2205双相不锈钢中σ相的析出规律.在950℃保温,当冷轧变形量从50%增大到85%时,σ相析出时间从30 min 缩短为3 min.冷轧变形量为85%的试样,在950℃保温,当保温时间从3 min 延长至30 min 时,σ相的体积分数从1.2%增大到11.8% .在 875~950℃保温5 min 后,当温度从875升高至950℃时,σ相的体积分数从8.9%降低至3.6%;在975℃保温5 min 后,组织中不存在 σ相.     

含钒超细晶双相钢的细化机制

利用铁素体+马氏体+贝氏体的初始显微组织结合冷轧和连续退火的方法达到了细化晶粒的目的,通过这种方式制备的双相钢中有63.8%的铁素体晶粒尺寸分布于0.5～1μm,有53%的马氏体晶粒尺寸分布于0.5～1μm.针对该现象研究了基于铁素体+马氏体+贝氏体初始显微组织含钒超细晶双相钢的晶粒细化机制.分析认为,细化机制主要有三个方面:第一是形变对显微组织的细化,包括为了得到铁素体+马氏体+贝氏体的初始显微组织而进行的热轧和冷轧;第二是冷轧态显微组织的再结晶和快速奥氏体化;第三是钒的析出物阻碍奥氏体的长大.     

核反应堆压力容器模拟钢中纳米富Cu相的变形特征

提高了Cu含量的核反应堆压力容器(reactor pressure vessel,RPV)模拟钢样品,经过880 cC水淬、660℃调质处理和400℃1000～4000 h的等温时效处理,观察到纳米富Cu相的析出;随后进行20%～30%冷轧变形,采用萃取复型(extractionreplica,ER)和高分辨透射电镜(high resolution transmission electron microscopy,HRTEM)的方法研究纳米富Cu相的变形特征.研究结果表明,镶嵌在α-Fe基体中的纳米富Cu相,在冷轧变形时的变形机制较为复杂,存在多种变形方式.当纳米富Cu相的晶体处于有利取向时,可以跟随基体一起发生滑移变形,表现为"软"颗粒的特性;当晶体处于不利取向时,会发生孪生变形,甚至诱发马氏体相变,有时生成"轮毂辐条"状的孪晶结构,大大提高了纳米富Cu相继续变形时的抗力,表现为"硬"颗粒的特征,因而析出纳米富Cu相会产生明显的强化作用.     

Influence of isothermal aging on σ precipitation in super duplex stainless steel

The time-temperature-transformation (TTT) curve of the 00Cr25Ni7Mo4N duplex stainless steel was obtained with a Formastor-digital thermal dilatometer, and the influence of isothermal aging on σ precipitation was studied by metallographic observation, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results show that the decomposition of ferrite phase is accompanied by the formation of σ phase at 750–1000℃, especially in the range of 800–900℃. The longer the aging time, the higher the amount of σ precipitation. The area fraction of various phases remains at a certain value upon the completion of ferrite deformation. The temperature of 850℃ is the most sensitive transaction temperature, the incubation time for the formation of σ precipitation is less than 1 min, and aging for 20 min leads to the complete transformation of ferrite. The σ phase is formed preferentially at the α/α/γ junction, and then grows along the α/α boundary in the matrix.     

Phase stability in an austenitic Fe-Cr-Mn (W,V) alloy

By means of deformation and long term aging, the stability and phase equilibrim characteristic of the C+N synthetically strengthening austenitic Fe-Cr-Mn (W,V) alloy were investigated. Experimental results indicate that the austenitic alloy remains stability and no γ→α transformation occurs under 500℃. Synthetic addition of C and N causes the grains to refine and powerfully retards formation of ε martensite and precipitation of σ phase. M_s point is elevated with long term aging at elevated temperature (500-700℃) due to a large number of strain induced carbides precipitate. Along with accelerated decomposition of strain induced α' martensite and occurrence of recrystallization, γ→α transformation and σ phase precipitation are promoted so that austenite becomes unstable.     

铍青铜QBe2合金形变时效工艺的研究

用正交试验的方法，对铍青铜QBe2合金形变时效工艺进行优选。试验表明，控制冷变形度、时效温度和时效时间，可获得高的硬度。给出了QBe2合金形变时效最佳工艺参数，以便在生产中采用。     

时效状态对Cu-Cr-Zr系合金性能的影响

采用不同时效状态和随后形变热处理工艺制备了Cu-Cr-Zr系合金,采用微观组织观察、硬度和导电率测试等手段研究了不同时效状态对双级时效Cu-Cr-Zr系合金性能的影响.结果表明：欠时效+冷轧+时效工艺和峰时效+冷轧+时效工艺制备的Cu-Cr-Zr-Mg-Si和Cu-Cr-Zr-Ni-Si合金均可获得力学性能和电学性能的优良组合.其中：欠时效+冷轧+时效工艺所制备的合金综合性能更优,但加工热处理过程中性能变化剧烈,材料生产过程中性能均匀性不易控制;峰时效+冷轧+时效工艺制备的合金综合性能极其稳定,易于在生产中控制.不同工艺下的合金性能差异是由析出相与位错的交互作用机制不同造成的.     

Microstruct ural evolution and mechanical behavior of metastable β -type Ti – 25Nb–2Mo – 4Sn alloy with high strength and low modulus

This paper presents a systematic study of newly developed metastable β-type Ti-25Nb-2Mo-4Sn (wt%) alloy with high strength and low elastic modulus, with focus on the microstructural evolution and mechanical behavior associated with aging. The pre-treatment (solution treatment or cold rolling) prior to aging exerts substantial influence on the subsequent aging response including microstructural evolution and mechanical behavior. Even under the same aging treatment, the aging products could be (β+ω), or alternatively (β+α), depending on the pre-treatments. This interesting aging response was discussed on the basis of the mechanism for ω formation. High-density dislocation tangles and grain boundaries induced by severe cold rolling play a key role in hindering the transition from β to isothermal ω, favoring the precipitation of α phase on aging. By aging cold-rolled specimen for short time, superior mechanical properties, i.e. high ultimate strength of ～1113 MPa and low elastic modulus of ～65 GPa, achieved in Ti-25Nb-2Mo-4Sn alloy. The characterization of microstructural evolution and compositional change indicated that the precipitation of fine α does not cause the enrichment of β-stabilizers in β matrix upon a short-time aging, guaranteeing low elastic modulus of the short-time aged specimen. Meanwhile, fine α precipitates as well as dislocations play a crucial part in strengthening, giving rise to its high yield strength and high ultimate tensile strength.