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选取羟基化多壁碳纳米管作为表面活性剂对TC4钛合金进行活性CO2激光焊接,焊后测量并计算了焊缝的熔深、熔宽及深宽比,观察分析了焊缝显微组织,测定了接头硬度和焊缝的物相组成。结果表明:TC4钛合金表面涂覆质量分数为4%的碳纳米管溶液,形成的涂覆层均匀致密;在给定焊接参数条件下,该涂覆层可使焊缝熔深增加约6%,熔宽降低约4%,深宽比增加约10%;涂覆碳纳米管可以增加激光吸收率,使得焊缝温度升高、冷却速率增大,因而涂覆碳纳米管的焊缝β晶粒较细,晶内的α'相较未涂覆碳纳米管的短小;碳纳米管对焊缝硬度和焊缝的物相组成无明显影响。 相似文献
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《宽厚板》2017,(6)
通过拉伸、冲击、硬度、焊后热处理等试验方法,研究了不同焊接热输入量对CO_2气体保护焊接条件下X100级管线钢焊接接头力学性能和显微组织的影响。结果表明:随着焊接热输入量增加,显微组织逐渐粗化;当焊接热输入量为1.91 kJ/mm时,焊缝中粒状贝氏体数量增多,针状铁素体数量减少,晶粒和M-A组元尺寸明显粗化,焊接接头的强韧性、硬度均下降;当焊接热输入量为1.17 kJ/mm时,其焊接接头能获得最佳的力学性能和显微组织。经过焊后热处理,距离焊缝2~4 mm处HAZ的HV10硬度为230~240,下降明显,焊缝硬度波动变小,距离焊缝4~6 mm处的HAZ和母材硬度变化不大。 相似文献
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激光—电弧复合焊兼具表面成形较好、熔深较大的特点,在中厚板焊接中获得广泛应用,但激光复合焊时,焊缝冷却速率较快,焊缝淬硬倾向较强,在中厚板低合金高强钢焊接时应用受限.针对宝钢生产的BG890QL低合金高强钢进行激光—电弧复合焊接,研究焊缝组织的淬硬倾向,结果表明:激光—电弧复合焊接接头柱状晶组织特定生长方向明显,但焊缝中心和顶部存在等轴晶.室温和-40℃时,焊缝处的冲击功分别为58 J和40 J,热影响区的分别为147 J和66.5 J,冲击性能均能满足要求.激光—电弧复合焊低合金高强钢可以获得强韧性较好的焊缝及热影响区组织,满足工程应用需求. 相似文献
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《稀有金属与硬质合金》2017,(5)
通过拉伸试验、硬度测试及金相分析等方法,对TC15钛合金激光焊接接头的显微组织和力学性能进行研究。结果表明,焊缝的深宽比在4~6之间波动,焊缝区域的晶粒形貌为柱状结构,且从焊缝中心线往外呈对称分布状态,主要为β相大晶粒。热影响区组织由细晶区、粗晶区及再结晶区构成,熔合线附近区域的晶粒明显粗化。焊缝区具有相对稳定的硬度值分布,硬度与热影响区的粗晶区相近。较低焊接电流焊缝试样具有最低的抗拉强度,其断裂部位为焊缝区;随着焊接电流的增大,焊接接头抗拉强度得到提高。 相似文献
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对厚度为25 mm的T851态2A97铝锂合金进行搅拌摩擦焊焊接,利用显微硬度、金相显微镜(OM)和透射电镜(TEM)等对焊缝的显微硬度和微观组织进行研究.结果表明:接头基材硬度最高,热影响区和热机影响区硬度降低,焊缝中心硬度又升高,硬度最低位置在热影响区.焊核区发生动态再结晶,形成细小等轴的晶粒;焊核区S′相全部溶解,T1相儿乎全部溶解,在随后的冷却和时效过程中,焊核区析出GP区和细小弥散的δ′相;热影响区的T1相部分溶解,S′相全部溶解,析出θ"相、δ′相和δ′/β′的复合相. 相似文献
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Yutaka S. Sato Hiroyuki Kokawa Masatoshi Enomoto Shigetoshi Jogan 《Metallurgical and Materials Transactions A》1999,30(9):2429-2437
The microstructural distribution associated with a hardness profile in a friction-stir-welded, age-hardenable 6063 aluminum
alloy has been characterized by transmission electron microscopy (TEM) and orientation imaging microscopy (OIM). The friction-stir
process produces a softened region in the 6063 Al weld. Frictional heating and plastic flow during friction-stir welding create
fine recrystallized grains in the weld zone and recovered grains in the thermomechanically affected zone. The hardness profile
depends greatly on the precipitate distribution and only slightly on the grain size. The softened region is characterized
by dissolution and growth of the precipitates during the welding. Simulated weld thermal cycles with different peak temperatures
have shown that the precipitates are dissolved at temperatures higher than 675 K and that the density of the strengthening
precipitate was reduced by thermal cycles lower than 675 K. A comparison between the thermal cycles and isothermal aging has
suggested precipitation sequences in the softened region during friction-stir welding. 相似文献
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S. J. Barnes A. R. Bhatti A. Steuwer R. Johnson J. Altenkirch P. J. Withers 《Metallurgical and Materials Transactions A》2012,43(7):2342-2355
A systematic set of single-pass full penetration friction stir bead-on-plate and butt-welds in HSLA-65 steel were produced using a range of different traverse speeds (50 to 500?mm/min) and two tool materials (W-Re and PCBN). Microstructural analysis of the welds was carried out using optical microscopy, and hardness variations were also mapped across the weld-plate cross sections. The maximum and minimum hardnesses were found to be dependent upon both welding traverse speed and tool material. A maximum hardness of 323?Hv(10) was observed in the mixed martensite/bainite/ferrite microstructure of the weld nugget for a welding traverse speed of 200?mm/min using a PCBN tool. A minimum hardness of 179?Hv(10) was found in the outer heat-affected zone (OHAZ) for welding traverse speed of 50?mm/min using a PCBN tool. The distance from the weld centerline to the OHAZ increased with decreasing weld speed due to the greater heat input into the weld. Likewise for similar energy inputs, the size of the transformed zone and the OHAZ increased on moving from a W-Re tool to a PCBN tool probably due to the poorer thermal conductivity of the PCBN tool. The associated residual stresses are reported in Part II of this series of articles. 相似文献
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CO2 laser beam welding of 6061-T6 aluminum alloy thin plate 总被引:1,自引:0,他引:1
Akio Hirose Kojiro F. Kobayashi Hirotaka Todaka 《Metallurgical and Materials Transactions A》1997,28(12):2657-2662
Laser beam welding is an attractive welding process for age-hardened aluminum alloys, because its low heat input minimizes
the width of weld fusion and heat-affected zones (HAZs). In the present work, 1-mm-thick age-hardened Al-Mg-Si alloy, 6061-T6,
plates were welded with full penetration using a 2.5-kW CO2 laser. Fractions of porosity in the fusion zones were less than 0.05 pct in bead-on-plate welding and less than 0.2 pct in
butt welding with polishing the groove surface before welding. The width of a softened region in the-laser beam welds was
less than 1/4 times that of a tungsten inert gas (TIG) weld. The softened region is caused by reversion of strengthening β″
(Mg2Si) precipitates due to weld heat input. The hardness values of the softened region in the laser beam welds were almost fully
recovered to that of the base metal after an artificial aging treatment at 448 K for 28.8 ks without solution annealing, whereas
those in the TIG weld were not recovered in a partly reverted region. Both the bead-on-plate weld and the butt weld after
the postweld artificial aging treatment had almost equivalent tensile strengths to that of the base plate. 相似文献
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针对某连退机组电阻搭接焊所存在的虚焊与过烧等焊接质量问题,分析确定影响焊接质量的主要因素,结合焊机的设备与工艺特点,建立了焊接过程熔核所需热量计算模型与焊接过程有效热量计算模型,实现了针对给定焊透率熔核所需热量和给定焊接工艺参数下所能获得的有效热量的定量预测计算。然后,提出以焊透率描述焊缝质量并以有效热量与熔核热量相等求解实现指定焊透率(即最优焊缝质量)的最佳焊接工艺参数,联立焊接过程熔核所需热量计算模型与焊接过程有效热量计算模型建立了一种焊接工艺参数设定方法和数学模型,形成一套连退机组搭接焊焊缝质量控制技术。将其应用到某钢厂连退机组生产线,提高了带钢的焊接质量,避免了虚焊与过烧等缺陷的发生,并为新钢种的开发减少了焊接试验时间与试验用料,创造了较大的效益。 相似文献
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Parameters controlling microstructure and hardness during friction-stir welding of precipitation-hardenable aluminum alloy 6063 总被引:1,自引:0,他引:1
Yutaka S. Sato Mitsunori Urata Hiroyuki Kokawa 《Metallurgical and Materials Transactions A》2002,33(3):625-635
The aluminum (Al) alloys 6063-T5 and T4 were friction-stir welded at different tool rotation speeds (R), and then distributions of the microstructure and hardness were examined in these welds. The maximum temperature of the
welding thermal cycle rose with increasing R values. The recrystallized grain size of the weld increased exponentially with increasing maximum temperature. The relationship
between the grain size and the maximum temperature satisfied the static grain-growth equation. In the as-welded condition,
6063-T5 Al was softened around the weld center, whereas 6063-T4 Al showed homogeneous hardness profiles. Different R values did not result in significant differences in the hardness profile in these welds, except for the width of the softened
region in the weld of 6063-T5 Al. Postweld aging raised the hardness in most parts of the welds, but the increase in hardness
was small in the stir zone produced at the lower R values. Transmission electron microscope (TEM) observations detected a similar distribution of the strengthening precipitates
in the grain interiors and the presence of a precipitation-free zone (PFZ) adjacent to the grain boundaries in all the welds.
Microstructural analyses suggested that the small increase in hardness in the stir zone produced at the lower R values was caused by an increase in the volume fraction of PFZs. 相似文献
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The effects of using oxygenated assist gases on the weldability and weld properties of Nd:YAG, pulsed laser welds in copper
(Cu) have been evaluated. It was found that the effective absorptivity of the Cu increased as the oxygen content of the Ar
assist gas was increased. This facilitated laser welding of Cu at much lower laser powers and increased weld penetration.
The use of oxygenated assist gas promoted nucleation and growth of submicroscopic oxide particles within the weld metal. These
particles dispersion-strengthened the weld metal, thereby increasing both weld metal hardness and strength. However, when
O2 concentrations in the assist gas were greater than 90 pct, weld metal embrittlement due to excessive volume fractions of
oxides was observed. The use of oxygenated assist gas also led to excessive cold lapping and poor bead quality. The bead quality
was improved, however, by ramping-down the laser power before terminating each pulse. 相似文献
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Akio Hirose Nobutaka Kurosawa Kojiro F. Kobayashi Hirotaka Todaka Hiroto Yamaoka 《Metallurgical and Materials Transactions A》1999,30(8):2115-2120
In welding 6061-T6 aluminum alloy, softening caused by the dissolution of strengthening β″ (Mg2Si) precipitates occurs in heat-affected zones (HAZs). Laser beam welding is advantageous in view of narrower softened regions.
The width of the softened region in a laser beam weld with a welding speed of 133 mm/s is 1/7 that of a tungsten inert gas
(TIG) weld with a speed of 5 mm/s. The hardness distributions and width of softened regions in the HAZ have been quantitatively
predicted to characterize the laser beam welding process. To this end, a kinetic equation describing the dissolution of age
precipitates has been established and has been applied to 6061-T6 aluminum weldments. The hardness profiles and the width
of softened zones have been successfully predicted in both welding processes. Prediction of the width of softened regions
with varying power inputs and welding speeds reveals that a high energy density and a high welding speed in laser beam welding
result in significantly narrower softened regions, in which the width is insensitive to variations in welding parameters compared
to that of TIG welding. 相似文献
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针对熔化焊在焊接AA7B04铝合金时易在焊缝中出现孔洞等缺陷,且接头性能下降明显、焊后变形大,以及采用铆接等机械连接方式会增加连接件的重量等问题,采用集成了搅拌摩擦焊末端执行器的KUKA Titan机器人对2 mm厚AA7B04高强铝合金进行了焊接,在转速为800 r·min-1的条件下,研究了焊度对焊接过程中搅拌头3个方向的受力Fx、Fy和Fz的影响.研究发现,Fz受焊速的影响显著,随焊速的增加而降低.利用光学显微镜、透射电子显微镜、拉伸试验、三点弯曲试验和硬度测试等方法,研究了不同焊速下AA7B04铝合金接头的微观组织和力学性能.结果表明:当焊速为100 mm·min-1时,接头的抗拉强度最高为447 MPa,可达母材的80%,且所有接头的正弯和背弯180°均无裂纹;接头横截面的硬度分布呈W型,硬度最低点出现在热力影响区和焊核区的交界处,焊速不同会导致不同的焊接热循环,且随着焊速的增加接头的硬度随之增加;焊核区组织发生了动态再结晶,生成了细小的等轴晶粒,前进侧和后退侧热力影响区的晶粒均发生了明显的变形;前进侧热影响区析出η'相,后退侧热影响区因温度较高析出η'相和尺寸较大的η相. 相似文献