Effect of post weld heat treatment on the microstructure and tensile properties of dissimilar friction stir welded AA 2219 and AA 6061 alloys

In the present work, the effect of post weld heat treatment on the microstructure and mechanical properties of dissimilar friction stir weldments of Al alloys 6061and 2219 (in peak aged T6 temper) was investigated. The survey of microhardness profile in the as-welded samples showed fluctuations across the weld zone and a minimum in the hardness occurred in the heat affected zone (HAZ) of alloy 6061. After a post weld ageing treatment at 165°C for 18h, the hardness was found to increase in weld zone alone and there is no effective improvement in HAZ hardness. On the other hand, a post weld solution treatment at 520°C followed by ageing at 165°C for 18h resulted in significant improvement in hardness across the whole weldment. This is also reflected in the tensile strength of the joint. These results were correlated with microstructures, observed using optical, scanning and transmission electron microscopes.     

搅拌摩擦加工IF钢的组织性能

对3 mm厚的DC04冷轧IF钢板进行搅拌摩擦加工,研究加工区域的微观组织与力学性能.在旋转速度为950 r·min^-1,加工速度为60 mm·min^-1时,采用加工后强制冷却技术可获得光滑平整且没有缺陷的加工表面.搅拌摩擦加工后组织显著细化,加工中心的平均显微硬度约为HV 135.6,是母材硬度的1.4倍,表面细晶层硬度最高可达到HV 312.8,细晶层和过渡层的抗拉强度分别比母材的抗拉强度提高50.9%和47.6%,加工前后试样的拉伸断口均呈微孔聚合韧性断裂特征.细晶强化对材料抗拉强度的提高起主要作用.     

6061-T6铝合金薄板的搅拌摩擦焊接

采用搅拌摩擦焊(FSW)技术对1 mm厚6061-T6铝合金薄板进行了对接.研究了焊接工艺参数的范围,实验测试了焊接接头的强度、硬度和延伸率,利用金相显微镜、扫描电镜和透射电镜分析了接头的微观组织.结果表明:对于1 mm厚度6061-T6铝合金,FSW的最优工艺参数为旋转速度1 800 r·min^-1,焊接速度1000 mm·min^-1;在此参数下,接头的硬度值达到母材的80%左右,抗拉强度达到母材的103%,延伸率达到母材的54%;接头的力学性能与微观结构相符.     

焊接速度对机器人搅拌摩擦焊AA7B04铝合金接头组织和力学性能的影响

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F_x、F_y和F_z的影响.研究发现,F_z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.     

Microstructure and mechanical properties of friction stir welding of AZ31B magnesium alloy added with cerium

The AZ31B magnesium alloy sheet added with 0.5 wt.% Ce was welded with friction stir welding(FSW).The microstructures and mechanical properties of the welded joint were investigated.The results showed that the microstructures in the weld nugget zone were uniform and with small equiaxed grains.The grains in the heat-affected zone and the thermo-mechanical affected zone were coarser than those in the base metal zone and the weld nugget zone.The ultimate tensile strength of AZ31B magnesium alloy added with 0.5...     

Fe-Cu-Sn烧结体的显微组织与力学性能

分别采用水雾化Fe-30%Cu合金粉末和单质Sn、Fe、Cu元素粉末为原料制备Fe-Cu-Sn合金,研究原料粉末和Sn含量(质量分数)对Fe-Cu-Sn烧结体致密度、冲击韧性、硬度和抗弯强度的影响。结果表明:与采用元素混合粉末相比,采用合金化程度较高的Fe-30%Cu(质量分数,下同)合金粉末为原料能大幅提高850℃烧结的Fe-Cu-5%Sn合金的致密度和力学性能,其致密度由82.8%提高到94.3%,硬度、冲击韧性和抗弯强度分别提高52%、84%和109%;当Sn的质量分数w(Sn)为3%～15%时,随着Sn质量分数增加,合金的硬度增大,冲击韧性和抗弯强度先增加后减小,其中w(Sn)为5%时,其抗弯强度和冲击韧性都较高,分别为977 MPa和11.6 J/cm2。当烧结体为双重结构组织时,其力学性能显著提高。     

国产A6N01铝合金型材MIG焊接头的微观组织与力学性能

利用金相观察、显微硬度测定、拉伸和弯曲性能测试等方法研究了A6N01-T5铝合金型材MIG焊接接头的显微组织和力学性能.结果表明：焊接接头焊缝中心金属为明显的激冷形成的铸态组织,呈等轴晶状;熔合区靠近焊缝侧的结晶形态为沿散热方向排列的柱状晶,邻近熔合区的热影响区晶粒粗化.焊缝中心处具有较高的显微硬度,在距离焊缝中心10~12 mm处的热影响区显微硬度值最低.国产A6N01-T5铝合金型材焊接接头抗拉强度达到欧洲标准DIN EN 288-4的要求.     

Structure and mechanical properties of 1570C alloy welds produced by friction stir welding

The effect of the conditions of friction stir welding (FSW) of 1570C aluminum alloy sheets on the structure and mechanical properties of the welded joints is studied. A recrystallized fine-grained structure with a grain size changing with the rate of welding tool rotation forms in a weld during FSW. As compared to the base metal, the yield strength of the weld metal decreases by 9–22% depending on the rate of welding tool rotation, and the ultimate tensile strength is almost independent of the FSW conditions and accounts for ～90% of the ultimate tensile strength of the base metal. The plasticity of the weld metal is >13% for all rates of welding tool rotation. The microstructure and mechanical properties of the weld zone are discussed.     

Microstructure and mechanical properties of Mg-10Y-2.5Sm alloy

The microstructure and mechanical properties of aged Mg-10Y-2.5Sm alloy were investigated.The results showed that the microstructure of the alloy consisted of α-Mg matrix and Mg24Y5 phase,and fine Mg24Y5 particles distributed in α-Mg matrix uniformly and dispersedly.Sm enhanced α-Mg matrix and Mg24Y5 phase by solid solution effect.At 200-300 oC,the ultimate tensile strengths were more than 200 MPa and the elongations were about 3%.Compared with those at room temperature,the mechanical properties had no obvious changes.     

镁稀土合金焊接工艺及组织性能研究现状与展望

随着航空航天、交通运输等领域对装备轻量化需求的提高,镁稀土合金因其比强度、比刚度大,抗蠕变能力强,高温力学性能优良等特点展现出广阔的应用前景.通过焊接工艺可以降低镁稀土合金大型复杂结构件的成型难度,有利于推广镁稀土合金在相关关键领域的进一步应用.本文围绕镁稀土合金的特性,介绍了镁稀土合金的性能及应用.着重讨论了稀土元素...     

真空轧制825合金/X65钢复合板的组织性能

 针对油气输送领域对耐H2S腐蚀油气复合管线的需求,采用真空轧制复合技术成功制备出825镍基合金/X65高强管线钢复合板。真空轧制复合技术是基于真空电子束焊接和热轧复合所开发出的一种新型复合技术,在高真空、高温和强塑性变形条件下,复合界面实现优异的冶金结合。采用X65/825合金/825合金/X65的4层对称复合轧制模式,并对复合界面的微观组织和力学性能特征进行分析。研究表明,复合界面连续平直,无孔洞和裂纹等缺陷,镍、铬和铁元素在界面两侧发生明显的扩散,另外复合界面生成一条连续的厚度约为1 μm的TiC薄带,在结合界面离散分布少量的颗粒状Al2O3化合物。界面平均剪切强度为404 MPa,拉剪断裂在复合界面处。     

Microstructure and mechanical properties of Mg-7Zn-3Al alloy with Nd and Y additions

The effects of combined addition of 0.6 wt.% Nd and 0.4 wt.% Y on the microstructure and mechanical properties of Mg-7Zn-3Al alloy were investigated.The results indicated that the Nd and Y addition led to obvious dendrite coarsening.However,it could modify the morphology and distribution of-Mg 32(Al,Zn) 49 intermetallics.Moreover,Al 2 REZn 2 phase could be introduced into the alloy with the Nd and Y addition.With the effective second-phase strengthening,the ultimate tensile strength and elongation in as-cast state can be improved by the Nd and Y addition.After ageing treatment,the alloy with the Nd and Y addition exhibited better precipitation strengthening effects by forming finer MgZn 2 and Mg 32(Al,Zn) 49 precipitates into the-Mg matrix.As a result,the yield and ultimate strength of Mg-7Zn3Al-0.6Nd-0.4Y alloy could be increased to 182 and 300 MPa by peak-ageing treatment.     

喷射成形6061铝合金的显微组织与力学性能研究

研究了喷射成形6061铝合金的显微组织和力学性能,并与熔铸成形6061铝合金进行对比。结果表明,喷射成形6061铝合金显微组织较好,但由于其还未进行致密化处理,组织内存在一定的孔隙,各项拉伸性能低于熔铸成形6061铝合金。     

大厚度紫铜搅拌摩擦焊接

采用搅拌摩擦焊接方法对厚度为30mm和50mm的T2紫铜板分别进行单面和双面焊接实验,并对焊缝的微观组织与力学性能进行了分析.结果表明:在一定的参数范围内,可获得表面成形美观、内部无缺陷且变形小的对接接头.30mm T2紫铜板单道焊焊后平均抗拉强度为177.2MPa,达到母材的81.7%,断后平均伸长率为25.4%;焊缝横切面显微硬度分布波动较大,最低值位于前进侧热影响区底部,说明了此处位置是焊缝薄弱环节.     

氮化物弥散强化铁基合金的显微组织和力学性能研究

本实验向雾化Fe-12.8Cr-3.4W铁基粉末中引入氮化物粉末进行球磨,然后对球磨粉末进行热挤压和热轧制制备得到合金样品。对雾化粉末和球磨粉末的形貌和成分、各组成形合金的显微组织、各组成形合金的力学性能以及断口形貌进行了研究。实验结果表明,球磨对粉末晶粒起到了细化作用,同时球磨后粉末与空气接触会引入少量的氧,YN(氮化钇)的引入起到了细化球磨粉末的作用;在氮化物弥散强化合金中检测到了尺寸小于100 nm的Ti N和TiO_2的复合弥散颗粒,少量弥散颗粒与合金中的Cr、W、Y和O元素结合长大形成大于100 nm的复杂化合物颗粒。采用氮化钇制备的合金抗拉强度与氧化钇合金基本相同,延伸率增加,同时显微硬度提高;采用氮化钛和氮化钇进行制备的合金显微硬度进一步增加。     

05CuPCrNi钢等离子弧焊焊接接头的组织与力学性能

 为了研究等离子弧焊在焊接薄板耐候钢时的优越性,对2 mm厚 05CuPCrNi耐大气腐蚀钢分别进行等离子弧焊与MAG焊(熔化极活性气体保护电弧焊)对接焊接,然后对焊接接头分别进行拉伸、弯曲、金相、硬度等试验,通过与MAG焊焊接接头的组织与力学性能对比,结果表明,与MAG焊相比,等离子弧焊时05CuPCrNi耐大气腐蚀钢焊接接头强度相对提高约6%,焊接接头组织为更均匀且细小的铁素体＋珠光体,并无MAG焊中出现的粗大块状铁素体及贝氏体,焊接热影响区较小,焊接接头弯曲性能良好,硬度值及硬度分布情况与MAG相近且无软化现象。     

Microstructure and mechanical properties of Mg-Zn-Y-Nd-Zr alloys

The microstructure and tensile properties of the as-cast and solution treatment Mg-4.5Zn-1Y-xNd-0.5Zr (x=0, 1 wt.%, 2 wt.%, 3 wt.%) alloys were investigated. The results showed that the microstructure of Mg-4.5Zn-1Y-0.5Zr alloy consisted of α-Mg, Zn-Zr, W (Mg₃Y₂Zn₃) and I (Mg₃YZn₆) phases. With the addition of Nd, I-phase disappeared and Mg₃Y₂Zn₃ phase changed into Mg₃(Nd,Y)₂Zn₃ phase. When the content of Nd reached 3 wt.%, T phase, i.e., ternary Mg-Zn-Nd phase, formed. In addition, with the increase of Nd content in the alloys, the secondary dendritic arm spacing decreased, while the amount of intermetallic phases increased. For as-cast Mg-4.5Zn-1Y-xNd-0.5Zr alloys, after solution treatment, microsegregation was eliminated and the shape of eutectic structure of α-Mg+W transformed from lamellar into spherical. The tensile strength and elongation of Mg-4.5Zn-1Y- 3Nd-0.5Zr alloy were increased from 219.2 MPa and 11.0% to 247.5 MPa and 20.0%, respectively.     

Microstructure and mechanical properties of Mg-Zn-Mn-Sn-Nd wrought alloys

The microstructure and mechanical properties of as-cast and extruded Mg-6Zn-1Mn-4Sn-xNd(x=0, 0.5, 1.0, 1.5) alloys were investigated by means of optical microscopy(OM), X-ray diffraction(XRD), scanning electron microscopy(SEM) and tensile test. The results showed that the dendrites sizes of these alloys were decreased by the addition of Nd. The phase compositions of the as-cast Mg-Zn-Mn-Sn-Nd alloys were dendritic α-Mg, MgZn2, Mg2 Sn, T phase and MgSnNd ternary phase. The mechanical properties of the as-extruded alloys were improved due to the refined equiaxed grains and dispersive Mg2 Sn and MgSnNd second phases. The comparison of the theoretical yield strength with the experimental yield strength revealed that the yield strength model of the as-extruded alloys should be modified as σys =σMg +σgb +σss +σsp.     

Microstructure and mechanical properties of copper alloyed austempered grey cast iron

Austempered grey cast iron (AGI) has emerged as a major engineering material in recent years because of its attractive mechanical properties. The main aim of this investigation is to assess the mechanical properties of copper alloyed AGI. Alloyed grey cast iron specimens are subjected to austempering heat treatment at six different temperatures for four different time periods. The resulting microstructures have been evaluated and characterised by means of light microscope and scanning electron microscope and X-Ray diffraction analysis. The microstructural features of AGI such as austenite content and its carbon content have been also found to influence the hardness, tensile properties and elongation. Both duration of the austempering time and the austempering temperature affect the mechanical properties of AGI. The hardness, tensile strength and ductility initially increase, and thereafter it decreases on longer periods of austempering. On the other hand hardness, tensile strength decreases as increasing austempering temperature, while ductility increases. The best combination of hardness 380BHN and strength 332?MPa; observed at 927°C of austenitising and 260°C of austempering temperature for 60?min.     

镁-钢无匙孔搅拌摩擦点焊接头机械连接状态分析

采用无匙孔搅拌摩擦焊对DP600镀锌钢和AZ31镁合金进行点焊搭接试验,利用扫描电镜观察其微观组织,分析拉伸断口推断其断裂过程.结果表明:镁-钢接头成形受转速与轴肩下压量影响敏感,可施焊工艺参数窗口小;在最优工艺参数下,接头成形良好,镁和钢相互嵌入锁合充分明显,具有典型"机械连接"特征;接头宏观形貌上,镁和钢分别呈多钩状互相嵌入对方并呈涡流状缠绕在一起;微观形貌上,由于搅拌针直接穿过钢板,钢侧搅拌针作用部分区域被撕裂与搅碎,镁、钢层叠交错分布,流向性明显,并存在少量由于镁蒸发造成的微观孔洞;拉断试验中,镁、钢分离起始于搅拌区外围不存在机械连接作用的区域,直至裂纹扩展至焊核区镁、钢互相缠绕部分钢的裂纹处,沿裂纹发生撕裂将钢板从镁板上剥离,断后在钢板的搅拌区域形成较大孔洞;接头横截面显微硬度显示,无论镁层钢层,其硬度分布均呈"W"型,符合普遍搅拌摩擦焊接头硬度分布特征.