电子束局部热处理对TC4合金接头疲劳性能影响

通过低周轴向应变疲劳试验,研究了电子束局部热处理对TC4钛合金接头疲劳性能的影响.结果表明,电子束局部热处理TC4钛合金接头在疲劳过程中存在一定的软化行为;在一定的载荷条件下,与焊后未热处理状态相比,经过电子束局部热处理后,TC4钛合金电子束焊接接头的疲劳寿命可以提高30%以上.     

镍基高温合金电子束焊接接头疲劳性能

对GH4169高温合金板材电子束焊接试样进行了金相分析和高、低周疲劳试验,分析GH4169合金的高、低周疲劳性能及疲劳断口形貌.结果表明,GH4169合金电子束焊接接头焊缝区的特点是树枝晶比较明显,为比较发达的树枝晶和明显的二次枝晶.在较高放大倍数下发现,母材和热影响区也为树枝晶结构.接头低周疲劳性能不低于母材,随应变幅降低,相同应变幅下焊接接头疲劳寿命变得略高于母材.接头高周中值疲劳强度比母材高约80 MPa.     

航空发动机涡轮盘GH4133B合金的疲劳断裂与组织研究

研究了不同应力幅值下航空发动机涡轮盘用GH4133B合金的疲劳性能,并观察了疲劳断口形貌。结果表明,GH4133B合金的理论疲劳极限均值为239.5 MPa;应力幅值为432 MPa时,疲劳断口无明显塑性变形,断口整体较为平整;疲劳源位于试样表面夹杂物处,在应力作用下向心部扩展,后断区位于外侧边缘,可见小面积剪切唇;合金中第二相颗粒在一定程度上会抑制疲劳裂纹的扩展,并减缓裂纹扩展速率。     

电子束热处理对钛合金接头残余应力的影响

采用小孔法,测量了BT20钛合金电子束焊接接头在焊态和电子束局部热处理两种状态下残余应力的分布。结果发现,钛合金电子束焊接接头处以纵向残余应力为主;通过电子束局部热处理,使焊缝处的残余应力峰值降低了约50％;在热处理的过程中,必须采取一定的措施,在改善残余应力的同时尽量避免产生变形。     

TC4钛合金焊接接头中压电子束局部热处理技术

电子束局部热处理技术是对整体热处理的一种有益补充,针对TC4钛合金进行中压电子束局部热处理研究。电子束局部热处理后TC4钛合金接头的组织形态与电子束焊态基本相同,但焊缝区的晶粒组织略有细化,焊缝区显微硬度也得到了改善,电子束局部热处理后焊接接头的拉伸力学性能均高于焊态。优化的电子束局部热处理工艺完全可以使TC4钛合金接头的组织力学性能超过焊态。     

真空电子束局部热处理技术的研究进展

介绍了电子束局部热处理技术的特点和意义，详细叙述了电子束焊后局部热处理的工艺以及设备的研究进展，提出电子束局部热处理技术发展的趋势及存在的问题。     

电子束局部热处理对TC4钛合金焊接接头组织和性能的影响

通过对14.5 mm厚TC4钛合金平板电子束焊接接头的局部热处理,研究了电子束局部热处理对钛合金电子束焊接接头组织、硬度和拉伸性能的影响.结果表明,电子束局部热处理后扫描区内的母材组织晶粒粗化长大,α相在原始β晶界处长大的同时,以层片状或针状的α形态向β晶内生长.局部热处理后冷却速度的降低使焊缝组织中的针状马氏体在分解析出β相的同时转变为α相,变短变厚的α相相互交错排列.另外,局部热处理消除了焊缝和热影响区的硬度突变.同焊后状态相比,局部热处理后焊接接头的整体性能沿焊缝垂直方向得到了均衡和提高,拉伸试样的断裂位置由焊后状态时的热影响区和母材的交界处转移到未经历热处理的母材区域.     

焊后热处理退火工艺对十字接头疲劳寿命的影响

通过对焊接结构疲劳评估标准分析,归纳了疲劳评估标准对焊接残余应力的考虑,阐明了从计算疲劳寿命角度看,残余应力不需要再另外考虑。设计并制作了一批十字接头试件,采用BS 7608:2014+A1:2015标准对疲劳试验数据进行了分析,结果表明,焊后退火前和不同工艺退火后的十字接头试件疲劳寿命没有显著差异。     

焊后热处理对GH4169合金闪光焊接接头组织与性能的影响

本文以GH4169高温合金闪光焊接件为研究对象,研究了热处理对焊缝试样的组织与力学性能的影响规律。结果表明,在焊接热量的作用下强化相γ′′、γ′发生回溶,致使焊接区的强度、硬度均明显低于基体。通过固溶处理后基体的强度降低到和焊缝试样一致,可实现拉伸变形过程中焊接区与基体的均匀变形。对焊缝试样在固溶前和固溶后进行1.2%拉伸塑性变形,经过时效处理(720 ℃8 h(60 ℃/h)-620 ℃8 h AC(空冷))后发现,少量塑性变形对其力学性能几乎没有影响。经固溶时效处理后焊缝试样拉伸强度指标与基体材料相比变化不大,但塑性指标低于基体试样,这与其热影响区存在粗大晶粒有关。     

预备热处理预防GH4133B合金精化模锻件低倍粗晶

介绍了预备热处理预防 GH41 3 3 B合金模锻件低倍粗晶的关键工艺参数 ,叙述了添加预备热处理后模锻件的性能变化及机理 ,并确定了预防低倍粗晶的工艺措施     

热处理工艺对一种新型铸造镍基高温合金的组织和性能影响

通过改变固溶热处理温度、保温时间和固溶后冷却方式,研究了不同固溶热处理工艺对一种新型铸造高温合金组织和性能的影响.结果表明,将合金在不同温度固溶处理2 h后空冷,合金在760℃,660 MPa和980℃,180 MPa条件下的持久寿命随热处理温度的升高先升高而后降低;固溶处理温度为1220℃时,760℃,660 MPa条件下的持久寿命达到最高;固溶处理温度为1180℃时,980℃,180 MPa条件下的持久寿命最高;当热处理温度从1120℃升高到1220℃时,拉伸强度随温度升高而增加,继续升温到1240℃,拉伸强度下降.当固溶热处理温度为1120℃,处理时间在2-8 h范围内变化时,合金在760℃,660 MPa条件下的持久寿命随时间延长而降低,而在980℃,180 MPa条件下的持久寿命随处理时间延长而升高;当热处理时间为2和4 h时,拉伸强度较高;延长到6和8 h时,拉伸强度下降.当冷却方式不同时,合金持久性能也发生变化.γ′相和γ/γ′共晶组织在尺寸、形态、分布和数量上的变化是导致合金力学性能变化的关键因素.     

热处理工艺对含Nb焊缝金属组织与力学性能的影响

采用含Nb及不含Nb两种焊丝对高速列车转向架用S355J2G3钢板进行焊接,分析了焊态下接头各区域的性能差别,研究了合金元素Nb和焊后热处理制度对焊缝金属组织和性能的影响.结果表明:焊缝金属的韧性是焊接接头性能的薄弱环节.焊态下Nb的加入提高了焊缝金属的强度,但对塑性和韧性无明显影响.经去应力退火后,不含Nb焊缝金属的强度降低,延伸率和冲击功升高,而含Nb焊缝金属的强度升高,延伸率和冲击功降低,退火后含Nb焊缝金属中NbC颗粒析出是影响焊缝金属组织和性能的主要因素.在焊后正火处理条件下,随着正火温度的升高,不含Nb焊缝金属的组织和性能均无明显变化,而含Nb焊缝金属的强度明显升高,延伸率和冲击功显著降低.严格控制正火温度是含Nb焊缝金属获得高强韧性的关键.含Nb焊缝中魏氏组织的含量随正火温度的升高而明显增多.电镜观察表明,经920℃正火处理后,焊缝中的NbC颗粒尺寸大于退火态焊缝金属中的NbC相,而在1200℃正火处理后NbC颗粒溶解消失.     

EFFECTS OF MICROSTRVCTURE ON FATIGUE CRACK GROWTH BEHMIOR IN Ni-BASE SUPERALLOY GH586

1.IntroductionInmetalsandalloys,thenearthresholdfatiguecrackgrowthisfrequentlytermed'microstructurallysensitive'.Thisisduebothtotheappearanceofthefracturesllrface,whichisoftenfaceted,andtotilelargevariationsincrackgrowthratewhichcanbeobtainedbyalteringparameterssllchasgrainsize,yieldstrength,ortherelativeproportionsanddistributionsofphasesinthemicrostructure[1].Thisimpliesthatsignificantimprotremelltintotalfatiguelifecouldbeachievedbychangingthemicrostructureofalloys.Therefore,itwouldbeveryadv…     

镍磷化学镀层对30CrMo钢疲劳性能的影响

通过三点弯曲疲劳试验研究了30CrMo钢经过化学镀Ni-9.5wt%P后的疲劳性能,用SEM观察分析了疲劳断口.结果表明,经200℃、400℃、600℃处理后,镀件的疲劳性能较基体分别下降了39%、52%、55%.分析认为,镀件的疲劳性能主要与镀层本身的疲劳性能及镀层的内应力有关.     

ON FATIGUE CRACK PATH DEVIATION AT ELEVATED TEMPERATURE IN ELECTRON BEAM REPAIRED WELDMENTS OF TURBINE DISK

Fatigue crack growth behaviors in electron beam weldments of a nickel-base superalloy are. studied. The objective of this paper is to discuss effects of the inhomogeneity of mechanical performance on fatigue crack growth (FCG) rate and crack path deviation (CPD). The base metal served in a turbine disk of aerospace engine was selected to fabricate bead-on-plate weldments by using electron beam welding. Some wedge-type opening loading specimens, notched in three different zone of weld metal, HAZ and base metal, were employed and performed fatigue crack growth tests at 650℃. The results show that the fatigue crack growth of electron beam welded joints is instable due to the influence of mechanical heterogeneities. Owing to the crack deviation at the weld metal and heat-affected-zone (HAZ), the effective growth driving force at the tip of fatigue crack was reduced with the reduction of the effective stress intensity factor (SIF) which finally causes fatigue crack rate decrease. Fatigue crack was strongly affected by size and the symmetrical characteristics of the plastic zone at the crack tip, which means that the integrity of the welded structure containing the fatigue crack mainly depended on the toughness of the low strenqth zone.     

铝合金电子束焊接气孔的分析

在电子束焊接试验的基础上,分析了6061-T6铝合金焊缝气孔产生的倾向和坡口表面焊前清理、焊片除气、焊接参数、预热以及重熔方法之间的关系.     

电场处理对GH3044合金腐蚀行为的影响

将电场处理技术应用于镍基变形高温合金GH3044,研究了电场对合金组织及腐蚀行为的影响。结果表明,电场处理后合金耐晶间腐蚀能力得到提高,随电场处理时间的延长腐蚀速率减小。在800℃、 6.4 kV/cm条件下,电场处理10 h后合金腐蚀速率为2.06 mm/a,与未经电场处理状态相比,降低幅度达37.33%。电场处理过程中合金晶内大量退火孪晶的产生,使原始大角度晶界与退火孪晶相交处原子重新排列,随电场处理时间的延长,大量的原始大角度晶界被取代,呈连续分布的合金元素贫化网络被隔断,导致腐蚀沟前进受到阻碍,从而改善合金晶界的腐蚀行为,提高合金耐晶间腐蚀能力。同时,电场处理促进合金中原子扩散,使普通大角度晶界两侧Cr、Mo等合金元素的贫化趋势降低,也是合金耐腐蚀性能得以改善的重要原因。     

EFFECTS OF HEAT TREATMENT AND ENVIRONMENT ON CRACK PROPAGATION RATE IN STEEL GC-4 UNDER CORROSION FATIGUE AND STRESS CORROSION

Comparative investigations were carried out of the effect of heat treatment regimes Jor steelGC-4(40CrMnSiMoVA)on its crack propagating rates,from corrosion fatigue,(da/dN)_(CF),or stress corrosion cracking,(da/dt)_(SCC),in media with various constituentsand pH values.Both(da/dN)_(CF) and(da/dt)_(SCC) accelerate with the increase of yield stressof the steel,yet the former is far less than the later.In comparison with media,the(da/dt)_(SCC) in distilled water is slightly greater than that in 3.5% NaCl solution,and the(da/dN)_(CF) in distilled water is far less than that in 3.5% NaCl solution.With the pH valueincreasing in 3.5% NaCl solution,the(da/dN)_(CF) lowers down and the(da/dt)_(SCC) speedsup.An explanation was also proposed with concept of the cyclic hardening and softening atcrack tip,as well as the crack closure and occluded cell effect.     

Microstructure and fatigue crack growth behaviour of electron beam welding in 30CrMnSiNi2A steel

The effects of two post-weld heat treatment processes on the microstructure and fatigue properties of the electron beam welded joints of 30CrMnSiNi2A steel were studied. Electron beam local post-weld heat treatment ( EBLPWHT) , in a vacuum chamber, immediately after welding and a traditional furnace whole post-weld heat treatment (FWPWHT) were accepted. The experimental results show that, after EBLPWHT, the main microstructure of weld is changed from coarse acicular martensite into lath martensite, and base metal is changed from ferrite and perlite into upper bainite and residual austenite, however the microstructures of different zones of joints in FWPWHT conditions are tempered sorbite. The fatigue crack growth rate da/dN of welds and base metal are not obviously changed among EBLPWHT, FWPWHT test and as-welded (AW) test, as the mechanical properties of materials have a certain but not large effect on the da/dN of welded joints. The resistance to near threshold fatigue crack growth data of welded joints can be largely improved by EBLPWHT and it is related to microstructure and crack closure effect.