搅拌摩擦加工对过共晶Al-Si-Fe合金组织及性能的影响

对过共晶Al-Si-Fe合金进行了搅拌摩擦加工(FSP),研究了不同FSP转速和道次对过共晶铝硅合金强度和组织的影响。其中,选择搅拌转速分别为750r/min、1050r/min和1500r/min,搅拌道次分别为1道、2道、3道。结果表明,合金经过FSP加工后,硅、含铁相等硬质第二相颗粒强烈细化,但随着搅拌转速的提高,硬质相颗粒细化效果变差,第二相颗粒平均粒径由11.7μm变为15.5μm。随着搅拌道次的增加,细化效果越发显著,第二相颗粒的平均粒径由11.7μm变为8.9μm。FSP加工后材料抗拉强度和延伸率较铸态大幅度提高。当搅拌转速为750r/min、道次为3时,材料的拉伸强度和延伸率分别由铸态的48MPa、0.43%提高到150MPa、2.97%。因此,经FSP后过共晶铝硅合金组织和力学性能得到极大改善。     

热挤压对再生Al-Si合金组织和性能的影响

对含铁量为1.23%的Al-Si再生铝合金进行热挤压及T6热处理,采用光学显微镜、扫描电子显微镜、万能拉伸机、显微硬度计等方法研究挤压比对Al-Si再生铝合金组织、富铁相形态特征及力学性能的影响规律,并探讨富铁相形态演变机制。研究结果表明:热挤压无法完全消除第二相的偏析,晶粒尺寸主要由第二相面积分数决定,并随着第二相面积分数的增大而逐渐减小,与挤压位置无关。晶粒尺寸随挤压比的增大而逐渐减小,挤压比为60时较10时平均晶粒尺寸减小25%。热挤压后,富铁相的平均长度较T6处理后铸态时降低81.6%以上,同时圆整度也提高5.2倍以上。富铁相的平均长度随挤压比的增大而略有降低,而圆整度则改善明显。热挤压后合金的拉伸力学性能均得到大幅提高,其中延伸率提高4.7倍以上,并随着挤压比的增大而逐渐提高。富铁相仍然是断裂最为主要的源头,断口类型随着挤压比的增大由韧-脆混合型断口转变呈韧性断口。     

等径角挤压对AZ31镁合金组织及力学性能的影响

研究了电磁连铸AZ31镁合金沿A路径经常规等径角挤压(ECAE)和两步ECAE变形后的微观组织与力学性能.结果表明:与预挤压态相比,常规ECAE态合金随着挤压道次的增加,晶粒不断细化,伸长率不断提高,但屈服强度与抗拉强度逐渐降低;两步ECAE可以使晶粒进一步细化,伸长率、屈服强度与抗拉强度均提高.伸长率、屈服强度与抗拉...     

Sm对ADC12铝合金变质效果影响的研究

采用光学显微镜、X射线衍射仪、扫描电镜及能谱仪等手段研究了1.0%(质量分数)的Sm变质对ADC12铝合金组织结构的影响。结果表明,加入1.0%的Sm能使合金中α-Al相和共晶硅相均得到明显细化,α-Al相二次枝晶间距由51μm减小到15μm,平均晶胞尺寸由90μm减小到40μm;共晶硅由粗大的针状变为尺寸较小的短棒状或圆球状,圆整度得到提高;变质后的合金中生成了高熔点Al11Sm3金属间化合物。     

机械零部件用高强镁合金加工工艺与组织性能研究

针对Mg-Gd-Y合金塑性较差的问题,研究了固溶态和不同温度锻造加工态高强Mg-Gd-Y合金的组织与性能。结果表明,固溶态Mg-Gd合金的晶粒尺寸不均匀,平均尺寸约225μm;当锻造加工温度为440℃和410℃时,合金中第二相的数量较多,大量弥散分布的第二相的存在可以抑制动态再结晶的形成;随着锻造加工温度的降低,Mg-Gd合金的抗拉强度和屈服强度呈现逐渐升高的趋势,在锻造加工温度为470℃时,Mg-Gd合金的断后伸长率达到最大值19.2%,降低锻造加工温度至440℃和410℃时,断后伸长率反而有所降低;固溶态Mg-Gd合金的拉伸断口呈现脆性断裂的特征;锻造加工温度为500℃的拉伸断口呈现混合断裂特征,而锻造加工温度为410℃、440℃和470℃时Mg-Gd合金的断口都呈现为韧性断裂特征。     

SiC对ML174铝合金组织及力学性能的影响

目的 改善ML174铝合金组织,提高其力学性能.方法 通过向ML174铝合金中添加不同质量分数的SiC,研究其对合金组织和性能的影响.结果 SiC在ML174铝合金中为形貌不规则的多边形,多存在于Si相附近,且有少量团聚现象.SiC粒子的质量分数为1.0％时,ML174铝合金组织得到细化的效果最佳,共晶硅由较宽的条带状变为细小的短棒状,分布更为均匀弥散,初晶硅的数量增多,尺寸减小,力学性能也有较大的提高,未添加SiC的合金室温抗拉强度和伸长率分别为370 MPa和0.6％,与添加后结果(405 MPa,1.0％)相比,其室温抗拉强度和伸长率分别提高了9.5％和66.7％.结论 SiC质量分数为1.0％时可以改善ML174铝合金组织并有效提高其力学性能.     

水下多道次搅拌摩擦加工对纯铜微观组织和力学性能的影响

目的 分别在空气中和水中对铜板进行单道次和多道次搅拌摩擦加工（FSP）,以此探究冷却介质和加工道次对纯铜微观组织和力学性能的影响。方法 选择厚度为3 mm的T2纯铜板分别在空气中进行1～2道次加工,在水下进行1～4道次加工。使用光学显微镜、显微硬度检测、扫描电子显微镜和拉伸试验机对加工后的试样进行微观组织和力学性能检测。结果 与空气中的搅拌摩擦加工相比,水下搅拌摩擦加工试样的表面质量更好;空气中搅拌摩擦加工试样的晶粒尺寸比母材的晶粒尺寸大,水下搅拌摩擦加工（SFSP）可以有效细化晶粒,并且随着加工道次的增加,晶粒尺寸逐渐增大,其中,1道次水下搅拌摩擦加工纯铜的晶粒尺寸最小（3.93μm）。显微硬度检测和拉伸试验结果表明,与空气中搅拌摩擦加工试样相比,水下搅拌摩擦加工试样的屈服强度和硬度更高,但随着加工道次的增加,样品的屈服强度和硬度都会有所降低。结论 水下多道次搅拌摩擦加工可以减小纯铜的晶粒尺寸,提升纯铜的力学性能。     

7075铝合金半固态浆料制备及流变压铸工艺研究

目的研究搅拌速度和搅拌时间对ACSR工艺制备的7075铝合金半固态浆料组织的影响,研究和比较传统压铸与流变压铸7075铝合金的组织与性能。方法通过改变搅拌速度和搅拌时间制备7075铝合金半固态浆料,取料水淬获得半固态坯料,将剩余浆料进行流变压铸,采用金相显微镜、扫描电子显微镜、万能试验机等研究了试样的微观组织、拉伸性能与断口形貌,探究搅拌速度和搅拌时间对7075合金半固态浆料组织的影响,同时研究与比较传统压铸与流变压铸7075铝合金的组织性能。结果在一定范围内提高搅拌速度和搅拌时间有利于α1-Al的细化与球化,与传统压铸7075铝合金相比,流变压铸合金具有更优异的力学性能,T6热处理后,其抗拉强度、屈服强度和伸长率分别为547 MPa、494 MPa和3.2%。结论 ACSR工艺可制备出组织细小圆整的7075铝合金半固态浆料,且流变压铸可改善7075铝合金力学性能。     

固溶时间对半固态挤压成形Al-17Si-4Cu-0.5Mg合金组织及力学性能的影响

采用半固态挤压成形工艺制备过共晶Al-17Si-4Cu-0.5Mg合金,研究固溶时间对过共晶Al-17Si-4Cu-0.5Mg合金组织及性能的影响.结果表明,随着固溶时间的增加,Si相出现球化,固溶时间为10 h时,共晶Si的圆整度为0.72.铸态下Si相周围富集较高浓度的Cu元素,固溶1 h后,Cu元素快速固溶到基体中.固溶时间从1 h增加到16 h,在XRD曲线上的θ(Al2 Cu)和Q(Al5 Si6 Cu2 Mg8)相的衍射峰强降低,合金基体中的位错密度大量减少.经180℃,时效处理12 h后,组织中析出针状的θ'相和短棒状的Q'相.随着固溶时间的增加,合金强度值呈现"双峰"现象.固溶1h后,合金的抗拉强度为269 MPa,屈服强度为233 MPa,与未热处理合金相比,抗拉强度和屈服强度分别提高了43.3％和42.7％,合金强度的提高是由于在固溶初期基体中仍有较大的位错密度,时效处理后析出相对位错有较强的钉扎阻碍作用.固溶时间为10 h时,合金的抗拉强度为311 MPa,屈服强度为263 MPa,达到第二个强度峰值,Si相的圆整化和细小析出相的弥散强化作用是形成第二个强度峰的主要原因.     

Al-Si-Cu-Fe压铸合金搅拌摩擦加工表面改性后的组织及冲蚀磨损性能

目前,通过搅拌摩擦加工(FSP)表面改性来改善材料表面冲蚀磨损性能的报道较少。对Al-Si-Cu-Fe过共晶压铸铝合金实施了搅拌摩擦加工(FSP),利用扫描电镜(SEM)、二次电子像(SEI)、背散射电子像(BEI)及冲蚀磨损试验机,研究了FSP对铸铝组织演化及表面冲蚀磨损性能的影响规律。研究表明:压铸合金中除α-Al基体外,第二相主要为共晶Si、β-Al3(Fe,Mn) Si2相以及少量的初晶Si;经过搅拌摩擦加工后,第二相的类别未发生变化,但α-Al相及第二相颗粒均被细化;压铸合金中第二相为长宽比较大的颗粒,受到冲蚀后发生断裂,使颗粒与基体间形成微孔洞;而FSP合金中第二相颗粒长宽比较小,且分布均匀,因此冲蚀过程中脆性断裂较少,从而降低了冲蚀磨损过程中合金的冲蚀率;压铸合金及FSP合金冲蚀率均随着冲蚀攻角增大而减小。     

AZ31镁合金薄板的无针搅拌摩擦加工

目的 研究有针、无针搅拌摩擦加工对AZ31镁合金薄板的微观组织和力学性能的影响.方法 通过搅拌摩擦加工技术(FSP)以不同的转速对AZ31镁合金薄板进行加工,采用拉伸试验机、金相显微镜、UMT摩擦磨损试验机、维氏硬度机对无针搅拌加工后的AZ31镁合金加工表面的晶粒形貌、拉伸性能、磨损性能和硬度进行研究分析,并与同转速有...     

Effect of welding speed on microstructural and mechanical properties of friction stir welded Inconel 600

In order to evaluate the properties of a friction stir welded Ni base alloy, Inconel 600 (single phase type) was selected. Sound friction stir welds without weld defect were obtained at 150 and 200 mm/min in welding speed, however, a groove like defect occurred at 250 mm/min. The electron back scattered diffraction (EBSD) method was used to analyze the grain boundary character distribution. As a result, dynamic recrystallization was observed at all conditions, and the grain refinement was achieved in the stir zone, and it was gradually accelerated from 19 μm in average grain size of the base material to 3.4 μm in the stir zone with increasing the welding speed. It also has an effect on the mechanical properties so that friction stir welded zone showed 20% higher microhardness and 10% higher tensile strength than those of base material.     

Influence of reinforcing particles on microstructure and mechanical properties of friction stir processed aluminium alloy AA7075-T651

This paper emphasis the improvement of mechanical properties of AA7075-T651 using friction stir processing through localized surface modification by adding nano boron carbide particles. The reinforcement techniques such as the groove and blind hole methods were used by changing reinforcements of nano boron carbide and a matrix of AA7075-T651 surface composites volume percentages (2 %, 4 %, and 6 %) along with tool rotational speed and processing speeds. Optical microscopy, scanning electron microscope and x-ray diffraction analysis were used to examine the particle dispersion for the surface composites and to correlate with the enhanced mechanical properties. Results revealed that high input parameters have given grain coarsening and precipitate agglomeration and low input parameters provide poor nugget metal consolidation and no vertical material flow. The L9 orthogonal Array designed and optimized the process parameters for enhancing the surface properties of processed samples. Mechanical properties like ultimate tensile strength, yield strength, hardness, percentage of elongation and impact strength were evaluated for the groove friction stir processing method and blind-hole friction stir processing methods. From the results, it has been observed that the blind-hole technique resulted in higher hardness and the homogenous dispersion of nano boron carbide particles in the stir zone than the groove method. Consequently, for blind-hole friction stir processing, grey relational analysis (GRA) and particle swarm optimization (PSO) approaches were proposed to optimise process parameters. From the compared optimization results between grey relational analysis and particle swarm optimization, particle swarm optimization approach was shown the best optimization results. Successively, the optimum condition in the respective experimentation is accomplished. Based on these observation and results, final validation tests were carried by changing the volume percentages of reinforcement keeping tool rotation speed and tool processing speed as constant. It is apparent that dynamic recrystallization in aluminium alloy at the processed zone due to presence of heterogeneous nucleation sites with nano boron carbide particles.     

水下搅拌摩擦焊对铝/铜接头组织与性能的影响

目的 采用搅拌摩擦焊,对比分析大气环境和水下环境下铝/铜接头的组织与性能,以期获得力学性能更优异的铝/铜焊接接头。方法 利用搅拌摩擦焊,在焊接速度为40 mm/min、旋转速度为1 000 r/min的条件下,分别在大气环境和水下环境下对厚度为9 mm的6061铝合金板和T2纯铜板进行焊接。然后,对铝/铜界面、焊核区进行扫描电镜及能谱分析,并对铝/铜界面及焊核区进行物相分析,确定产物相组成。最后,对铝/铜试样进行拉伸及硬度检测。结果 铝/铜接头均无裂纹、气孔等缺陷。铜颗粒弥散分布在焊核区,铝/铜界面形成金属间化合物层。水下搅拌摩擦焊下界面元素扩散距离明显变短,且金属间化合物厚度更薄。铝/铜接头的金属间化合物为AlCu和Al4Cu9。大气环境焊接下接头的抗拉强度为130.6 MPa,断裂方式为脆性断裂;水下焊接下接头的抗拉强度为199.5 MPa,断裂方式为韧性断裂。水下环境下的接头硬度值更高,其中热影响区的硬度最低值约为65HV。结论 水下搅拌摩擦焊铝/铜接头无裂纹、气孔等缺陷。组织上,水下搅拌摩擦焊的铝/铜接头界面元素扩散距离更短,硬脆的金属间化合物更少;性能上,水下搅拌摩擦焊的铝/铜接头强度更高,抗拉强度达到199.5 MPa,达到母材的74.4%。     

搅拌摩擦加工法制备碳纳米管增强铝基复合材料

为了制备晶粒细小、 组织均匀的复合材料, 提高材料的力学性能, 用搅拌摩擦加工法制备碳纳米管增强铝基复合材料, 并对不同碳纳米管含量的复合材料的微观结构、 拉伸性能及断口形貌进行分析。结果表明: 碳纳米管添加到铝基体中, 搅拌摩擦中心区晶粒细小, 碳纳米管与基体之间结合良好, 未发现明显的缺陷; 碳纳米管对基材有明显的强化作用, 铝基复合材料抗拉强度随着碳纳米管含量的增加而提高; 碳纳米管体积分数为7%时, 抗拉强度达到201 MPa, 是基材的2.2倍; 复合材料在宏观上呈现脆性断裂特征, 微观上呈现韧性断裂特征, 其断裂机制以CNTs/Al界面脱粘、 基体撕裂和增强体断裂为主。      

Investigation on high-temperature mechanical properties of Al–7Si–0.6Mg alloy by wire + arc additive manufacturing

The room temperature and high temperature tensile properties of Al–7Si–0.6Mg alloy prepared by wire arc additive manufacturing have been investigated. The results show that the strengthening phase gradually coarsens and the eutectic silicon phase does not grow and agglomerate, meanwhile, the tensile strength and yield strength of the alloy gradually decrease with the increase of temperature. The high-temperature properties of the alloy are better than that of cast alloy. With the increase of temperature, the fracture of the alloy changes from ductile transgranular fracture to intergranular fracture.     

镁合金高转速搅拌摩擦焊工艺研究

目的 研究镁合金高转速搅拌摩擦焊工艺及其对组织与性能的影响规律。方法 采用光学显微镜观察以及拉伸性能测试等方法,探索了1.5 mm厚AZ31B镁合金高转速搅拌摩擦焊接工艺,对其接头组织与力学性能进行了测试分析。结果 采用6000 r/min转速时,随着焊速从600 mm/min降低至100 mm/min,焊接接头隧道型孔洞缺陷消失;采用600 mm/min焊速时,2000~4000 r/min转速范围内可获得无缺陷的接头。拉伸测试结果表明,6000 r/min-100 mm/min焊接工艺下接头的拉伸性能最优,抗拉强度为235.33 MPa,为母材强度的87.92%。结论 镁合金采用高转速搅拌摩擦工艺可获得无缺陷的焊接接头,且采用高转速匹配低焊速的工艺可使接头的拉伸性能得到提升。     

Microstructure and mechanical properties as a function of rotation speed in underwater friction stir welded aluminum alloy joints

A 2219-T6 aluminum alloy was underwater friction stir welded at a fixed welding speed and various rotation speeds in order to illuminate the influence of rotation speed on the performance of underwater joints. With increasing rotation speed, the hardness of the stir zone (SZ) gradually increases due to the increase in dislocation density. The tensile strength first increases from 600 to 800 rpm and then reaches a plateau in a wide rotation speed range. After that a remarkable decrease in tensile strength occurs owing to the formation of void defect. The joint welded at lower rotation speed tends to be fractured in the SZ. At higher rotation speeds, the hardness increase in the SZ makes the fracture locations of defect-free joints move to the thermal-mechanically affected zone (TMAZ) or heat affected zone (HAZ).     

Effect of welding speed on microstructures and mechanical properties of underwater friction stir welded 2219 aluminum alloy

Underwater friction stir welding (underwater FSW) has been demonstrated to be available for the strength improvement of normal FSW joints. In the present study, a 2219 aluminum alloy was underwater friction stir welded at a fixed rotation speed of 800 rpm and various welding speeds ranging from 50 to 200 mm/min in order to clarify the effect of welding speed on the performance of underwater friction stir welded joint. The results revealed that the precipitate deterioration in the thermal mechanically affected zone and the heat affected zone is weakened with the increase of welding speed, leading to a narrowing of softening region and an increase in lowest hardness value. Tensile strength firstly increases with the welding speed but dramatically decreases at the welding speed of 200 mm/min owing to the occurrence of groove defect. During tensile test, the joint welded at a lower welding speed is fractured in the heat affected zone on the retreating side. While at higher welding speed, the defect-free joint is fractured in the thermal mechanically affected zone on the advancing side.     

Through-thickness microstructure and mechanical properties in stationary shoulder friction stir processed AA7075

Stationary shoulder friction stir processing of high strength thick AA7075 aluminium alloy demonstrated tiny gradient in the microstructure refinement across the thickness, which was attributed to the less heat input and small temperature gradient by the stationary shoulder. Stationary shoulder produced a very smooth surface finish with a little amount of flash throughout the processing area. Probe-dominated stir zone (SZ) resulted in uniform grain refinement as well as hardness distribution across the SZ thickness. The ductility in SZ increased by 48% in comparison to the unprocessed material without costing tensile strength. This tensile behaviour trend maintained throughout the thickness in SZ.