高Mg含量Al-Mg-Sc-Zr合金选区激光熔化成形性及力学性能

基于宽粒径分布粉末(2~46μm),应用选区激光熔化(SLM)技术制备了高Mg含量Al-14.4Mg-0.33Sc-0.19Zr铝合金。系统研究了不同工艺参数和时效处理条件对合金SLM成形性、组织和力学性能的影响。结果表明,高激光功率可有效降低细粉飞溅对样品成形性的干扰,SLM成形样品的最大相对密度为98.6%。样品显微组织由熔池边界细小等轴晶和熔池内部粗大晶粒构成,Mg含量的增加降低了样品织构和柱状晶的含量。经不同温度时效处理后,SLM成形样品的硬度先增加后降低,在350℃时具有最大值。SLM成形样品在350℃时效处理时,硬度和压缩屈服强度均随时效时间的增加出现双峰值现象,时效1 h后样品的硬度(HV)和屈服强度均达到最大值,分别为(1670±30)MPa和(457±10)MPa,延伸率为(27±3)%。样品经350℃长时间时效处理后,由于第二相粒子的粗化,导致样品的硬度和强度有所降低。本研究通过保留铝合金粉末的细粉区,有效提升了粉末的利用率,降低了原料成本,获得了成形性和力学性能较优的高Mg含量SLM成形Al-Mg-Sc-Zr铝合金。     

高Mg含量Al-Mg-Sc-Zr合金选区激光熔化成形性及力学性能

基于宽粒径分布粉末(2~46μm),应用选区激光熔化(SLM)技术制备了高Mg含量Al-14.4Mg-0.33Sc-0.19Zr铝合金。系统研究了不同工艺参数和时效处理条件对合金SLM成形性、组织和力学性能的影响。结果表明,高激光功率可有效降低细粉飞溅对样品成形性的干扰,SLM成形样品的最大相对密度为98.6%。样品显微组织由熔池边界细小等轴晶和熔池内部粗大晶粒构成,Mg含量的增加降低了样品织构和柱状晶的含量。经不同温度时效处理后,SLM成形样品的硬度先增加后降低,在350℃时具有最大值。SLM成形样品在350℃时效处理时,硬度和压缩屈服强度均随时效时间的增加出现双峰值现象,时效1 h后样品的硬度(HV)和屈服强度均达到最大值,分别为(1670±30) MPa和(457±10)MPa,延伸率为(27±3)%。样品经350℃长时间时效处理后,由于第二相粒子的粗化,导致样品的硬度和强度有所降低。本研究通过保留铝合金粉末的细粉区,有效提升了粉末的利用率,降低了原料成本,获得了成形性和力学性能较优的高Mg含量SLM成形Al-Mg-Sc-Zr铝合金。     

选区激光熔化Zr改性Al-Si-Mg合金组织和力学性能

针对选区激光熔化（SLM）高Mg含量AlSiMg3合金成形性差的缺点,通过Zr进行合金化,研究了工艺参数对SLM成形高Mg含量Al-Si-Mg-Zr合金的成形性及时效处理对合金组织和力学性能的影响。结果表明,SLM成形Al-Si-Mg-Zr合金的熔池边界处形成了大量的细小等轴晶,从而有效地避免了样品在成形过程中裂纹的产生,增加了样品的SLM成形性,不同激光功率和激光扫描速度下获得样品的孔隙率均低于0.3%。拉伸测试结果表明,成形态样品的屈服强度（YS）为(426±8) MPa,极限抗拉强度（UTS）为(464±12) MPa。经165℃时效处理后,由于α-Al晶粒内部纳米强化相的增多,样品的强度增加明显,时效样品的最大YS和UTS分别为(482±11)MPa和(522±10)MPa。本研究获得SLM成形Al-Si-Mg-Zr样品的强度高于目前商用的SLM成形Al-Si-Mg合金。     

选区激光熔化专用AlSiMg合金成分设计及力学性能

应用"团簇+连接原子"模型,基于合金液-固局域结构相容性和金属选区激光熔化(SLM)工艺熔体急冷的技术特性,设计高Mg含量SLM专用AlSiMg1.5合金新成分,系统研究时效温度和时间对SLM成形AlSiMg1.5合金显微组织和力学性能的影响。结果表明,通过调整工艺参数,可获得近乎全致密的SLM成形样品。当时效温度为300℃时,随着时效时间的延长,SLM成形样品岛状富Al组织中过固溶Si逐渐析出长大,网格状富Si组织逐渐分解球化,样品的硬度和压缩屈服强度逐渐降低,塑性明显增加。当时效温度为150℃时,不同时效时间下SLM成形样品的显微组织没有发生明显变化,但硬度和屈服强度随时效时间的延长先增大后略有降低。SLM成形AlSiMg1.5样品经150℃时效处理后的最大显微硬度和压缩屈服强度分别为(169±1) HV和(453±4) MPa,样品延伸率超过25%。本工作设计获得了成形性和力学性能优异的SLM专用铝合金新成分Al91.0Si7.5Mg1.5(质量分数,%)。     

选区激光熔化成形AlSiMg3合金

基于选区激光熔化（SLM）技术熔体快速冷却的特点，通过提高Al-Si-Mg合金中Mg的含量，设计获得SLM技术专用AlSiMg3合金。系统研究了不同工艺参数和时效处理条件对SLM成形AlSiMg3合金组织和硬度的影响。结果表明，SLM成形样品均由α-Al、Si和Mg2Si相构成。高激光能量密度有利于增加粉末样品的成形性，当激光功率为160 W，扫描速度为200 mm/s时，样品具有最低孔隙率0.07%。随着激光扫描速度的增加，样品中富Si组织的比例逐渐升高，Mg元素在α-Al中固溶量逐渐增大，使得SLM成形样品的硬度逐渐升高，最大值为194±3 HV。样品经150 ℃时效处理后，由于α-Al内部纳米颗粒的析出，导致样品硬度增大，最大值为210±2 HV，远高于现有报道的SLM成形Al-Si和Al-Si-Mg铝合金。本研究报道了成形性和力学性能优异的SLM专用Al-Si-Mg合金。     

激光选区熔化成形K4202镍基铸造高温合金的组织和性能

针对激光选区熔化(selective laser melting,SLM)制造K4202合金复杂金属零件在航空航天等领域的应用需求,以K4202合金粉末为材料,研究了该合金的SLM成形工艺、成形态和热处理后的显微组织和力学性能.结果表明,K4202合金SLM成形试样显微组织由树枝晶和等轴晶构成,树枝晶生长方向多与熔池边界近似垂直.固溶+时效处理后,由于再结晶的发生,SLM成形所形成的树枝晶结构完全消失,同时晶界和晶内有金属碳化物析出.时效处理后的组织与SLM成形态相比,变化并不明显,其树枝晶结构保存较完整,晶界处同样有碳化物析出.SLM成形试样的拉伸性能优于传统铸造方法,通过固溶+时效处理和时效处理,试样的屈服强度、抗拉强度均提升显著,但塑性下降明显,其中时效处理后的拉伸强度最高.     

选区激光熔化铝合金的组织和性能各向异性研究

基于Al-4.8Mn-1.7Mg-0.75Sc-0.75Zr铝合金,研究了各向异性对合金显微组织及力学性能的影响。结果表明,选区激光熔化制备出无裂纹致密合金样品,纵截面显微组织有典型熔池结构,由细等轴晶粒和长柱状晶组成,横截面显微组织有条带状结构,由细等轴晶组成。经时效处理后,横向试样屈服强度、抗拉强度和伸长率分别是512 MPa、540 MPa和15%,而纵向试样的屈服强度、抗拉强度和伸长率分别是502 MPa、536 MPa和12%,力学性能各向异性不显著。     

选区激光熔化法制备的M2052锰铜合金的组织与性能

使用真空感应熔炼气雾化法(VIGA)制备M2052锰铜粉末,通过选区激光熔化技术(SLM)直接成形合金试样,经固溶时效处理和热等静压加工,从热力学计算、显微组织分析及力学性能测试等方面对SLM法制备的锰铜合金进行了研究。研究发现SLM法成形的锰铜合金的抗拉和屈服强度较高,但冲击吸收能量低,塑性差。经过热等静压处理后,合金的综合力学性能明显提高。     

热处理对SLM18Ni300马氏体时效钢组织及腐蚀性能的影响

目的探究热处理对激光选区熔化(SelectiveLaserMelting,SLM)成形18Ni300马氏体时效钢组织和耐腐蚀性能的影响。方法利用激光选区熔化技术成形18Ni300马氏体时效钢试样,分别对成形试样进行时效处理和固溶+时效处理。通过金相显微镜、扫描电镜、显微硬度计和电化学工作站,分别测试分析了不同热处理SLM 18Ni300马氏体时效钢的微观组织、显微硬度和耐蚀性。结果热处理后,试样微观组织发生显著变化,时效试样组织细化,得到板条马氏体组织;固溶+时效试样激光熔池消失,组织为均匀致密的板条马氏体,且均有细小析出物弥散分布于晶界和板条间。时效处理和固溶+时效处理显著提高了SLM18Ni300马氏体时效钢硬度,SLM试样硬度为376.6HV1,时效试样和固溶+时效试样硬度分别为651.5HV1和641.8HV1。0.5 mol/L H2SO4溶液中,SLM试样的Jcorr最小,为1.375×10?3 A/cm2,耐腐蚀性最好,各试样耐蚀性优劣有SLM试样固溶+时效试样时效试样。3.5%NaCl溶液中,SLM试样的极化曲线有明显的钝化平台,且Jcorr最小,为3.630×10?6A/cm2,耐腐蚀性最好,各试样耐蚀性优劣有SLM试样时效试样固溶+时效试样。结论时效处理和固溶+时效处理后,SLM 18Ni300马氏体时效钢得到板条马氏体组织,硬度显著提高,但在H2SO4溶液和Na Cl溶液中的耐腐蚀性能有所下降。     

选区激光熔化成形ZL205A合金工艺及性能研究

利用选区激光熔化(SLM)技术制备了ZL205A合金,研究了激光能量密度对SLM成形试样显微组织和力学性能的影响。结果表明,ZL205A合金粉末SLM成形试样中微观组织分为3个区域:细晶区、热影响区(HAZ)和粗晶区。在一定的范围内,随着能量密度增大,ZL205A合金粉末SLM成形试样的抗拉强度和屈服强度都先增加后减小。当能量密度为104.20J/mm3时,SLM成形ZL205A合金试样的抗拉强度、屈服强度达到最大,分别为289、230MPa,此时伸长率为4.2%。     

Microstructure and properties of AlSi7Mg alloy fabricated by selective laser melting

The AlSi7Mg alloy was fabricated by selective laser melting (SLM), and its microstructure and properties at different building directions after heat treatment were analyzed. Results show that the microstructure of SLM AlSi7Mg samples containes three zones:fine grain zone, coarse grain zone, and heat affected zone. The fine-grain regions locate inside the molten pool, and the grains are equiaxed. The coarse-grain regions locate in the overlap of molten pools. After T6 treatment, the microstructure at the molten pool boundary is still the network eutectic Si, but the network structure becomes discrete, and is composed of intermittent, chain-like eutectic Si particles. The yield strength at three directions (xy, 45°, z direction) of the AlSi7Mg alloy samples fabricated by SLM is improved after T6 heat treatment. The fracture mechanism of the samples is a mixed ductile and brittle fracture before heat treatment and ductile fracture after heat treatment.     

Enhanced Strength in Cu-Ag-Zr Alloy by Combination of Cold Working and Aging

In this investigation, the effect of different degree of cold rolling and post-aging treatment on the microstructure and mechanical properties of a Cu-3wt.%Ag-0.5wt.%Zr alloy was studied by means of hardness measurement, tensile tests, optical and electron microscopy. The alloy was subjected to cold rolling up to 80% followed by aging in the temperature range of 400-500 °C. The yield strength, ultimate tensile strength and hardness were found to increase as degree of cold rolling increased, but at the expense of ductility. Aging of cold rolled samples in the studied temperature range has resulted in different combinations of strength and ductility. However, aging of cold rolled samples at 400 °C for 1 h has resulted in a combination of high strength and moderate ductility. A yield strength and ultimate tensile strength of 511 and 560 MPa, respectively with a ductility of 12% were achieved for 80% cold rolled and aged (400 °C for 1 h) sample. The high strength achieved after 80% cold rolling and aging is mainly attributed to precipitation of fine silver precipitates.     

激光立体成形Ti60合金组织性能

研究激光立体成形(Laser Solid Formed,LSF)Ti60合金热处理(双重退火980℃,2hAC+650℃,3hAC)前后的组织形成规律,分析其在室温和高温(600℃)下的拉伸性能。研究发现:Ti60合金在激光立体成形过程中由于熔池顶部形成的等轴晶层占有一定的比例,在熔覆新层时未被完全覆盖,在整个熔覆层中呈现出等轴晶的宏观形貌,并出现了层带组织。Ti60合金激光沉积态显微组织为魏氏组织,由大量沿原始等轴β晶界向晶内生长的α板条束和少量板条间β相组成,成形件室温和高温强度分别高于锻造件,室温塑性比锻造件低,而高温塑性超过锻态;经过双重退火后,成形件中的层带组织消失,晶界α相被打断,不连续分布在原始的β晶界处,晶内α板条粗化,并部分球化,这使得室温和高温强度略有下降,但塑性增高,综合力学性能提高。     

激光能量输入对直接激光沉积莫来石陶瓷组织性能的影响

研究了激光能量密度对直接激光沉积熔体自生莫来石陶瓷孔隙/密度、微观组织和力学性能的影响。结果表明,较低激光能量密度(15 J/mm²)所制备的陶瓷样件边缘分布有尺寸较大的气孔,使得样件整体孔隙率较高,且表面粘粉严重,这与成形扫描速度大和硅酸盐熔体粘度高有关。而较高激光能量密度(90 J/mm²)虽然可以获得表面光滑、莫来石晶粒尺寸较小的陶瓷样件,但由于单位时间内输入熔池能量高,粉末蒸发产生的气孔来不及逃逸出熔池,使得样件心部形成较大的气孔,影响样件的力学性能。在激光能量密度为45J/mm²时,获得了表面相对光洁、孔隙率较低和力学性能较好的莫来石陶瓷样件。本研究结果为直接激光沉积增材制造高性能陶瓷过程中合理选定工艺条件提供了理论指导及技术支撑。     

不同送粉速度对TC4钛合金表面激光熔覆的影响

采用光纤激光对TC4钛合金表面进行熔覆改性,研究送粉速度对熔覆工艺过程和熔覆层性能的影响。采用高速摄像机拍摄了加热粉末在空间的分布形貌,采用光学显微镜观察了熔覆层横截面形貌,采用EDS分析了熔覆层的氮含量分布,并测量了熔覆层横截面的显微硬度。实验表明,送粉速度较小时,粉末吸收少量激光能量,熔池较大,熔覆层宽而浅;送粉速度较大时,粉末吸收大量激光能量,熔池较小,熔覆层窄而深。当送粉速度较大时,熔覆层的氮元素含量和显微硬度均分布基本均匀,无明显梯度;随送粉速度增加,熔覆层显微硬度会增加,并稳定在约9.3 GPa。     

Porosity formation mechanism and its prevention in laser lap welding for T-joints

A high-speed camera and X-ray transmission observation system were used to observe the keyhole and molten pool dynamic behavior in laser lap welding T-joints. The oscillation frequency of the molten pool and the keyhole increases with increasing gap. The lower keyhole becomes slant with the large gap and large quantities of bubbles are formed at the bottom tip of the keyhole. The molten pool is divided into three different zones by the large gap and a small eddy is formed at the lower molten pool. The bubbles are difficult to escape from the lower molten pool and the gap when the gap is large, resulting in the formation of porosity at the gap and root of weld seam. The distribution characteristics of porosity in different gap have an excellent agreement with the keyhole and the molten pool dynamic behavior. Porosity can be suppressed by maintaining a small gap or adopting high welding speed. The paper provides fundamental insights into the mechanism of porosity formation during laser lap welding T-joints and guidance to aid in its elimination.     

开放条件下气流对激光重熔过程中氧化行为的影响

在激光加工过程中,保护气和载粉气对熔池氧含量有很重要的影响,为了减少在开放条件下激光加工过程中产生的氧化,需要研究保护气和载粉气工艺参数对激光加工过程中氧化行为的影响。以激光重熔45钢为例,通过测定熔池上方气氛以及重熔后基材表层的氧含量,对比研究了不同保护气流量、载粉气流量和离焦量对激光重熔过程中氧化行为的影响。结果表明：气流量较低时,气流卷吸周围空气,载粉气流量、保护气流量以及离焦量升高会加剧激光重熔时的氧化。当载粉气流量超过84 L/min时,大量氩气对周围空气进行了稀释,熔池上方气氛中的氧含量会有所降低。但是保护气流量过高会加剧熔池飞溅。降低熔池上方气氛中氧含量的气流量工艺参数为：保护气流量8.5 L/min,载粉气流量6.5 L/min。     

能量约束的单晶高温合金激光外延修复试验研究

针对单晶高温合金激光外延修复层中常常出现"杂晶"的问题,提出能量约束的单晶高温合金激光外延修复工艺,并研究了激光功率和单晶母材宽度对修复层形貌与组织结构的影响。结果表明,能量约束的单晶高温合金激光外延修复层内几乎保持完全的定向外延生长枝晶,"杂晶"出现的概率大大降低。在优化参数下,修复层内获得连续的定向外延枝晶,单层厚度达到1220μm。随着激光功率升高,修复层厚度有所增加;在光斑直径和激光功率相同的条件下,随着单晶母材宽度的增加,修复层厚度先增加后减小,并呈现"扁平化"特征。当母材宽度为3mm时,修复层内呈现明显的流线特征,结合高速摄像照片,观察发现激光熔覆时熔池内金属从中心底部向表面流动,随后向四周扩散,最终沿着熔池底部回流至中心底部,如此反复。     

Joint strength and behaviour of coated aluminium in laser lap welding of steel sheets

When galvanized steel sheets are closely overlapped and welded by laser lap welding, a large amount of molten metal spatters, resulting in a poor surface appearance of the weld and weakened strength of the welded joint, as compared with that of cold-rolled steel sheets. Whereas in the case of aluminium-coated steel sheets, even when they are closely overlapped and welded by laser lap welding, no spattering occurs. Thus, a good surface appearance of the weld is obtained, but the welded joint has lower strength. In both the mentioned cases, it is known that if a clearance of about 0.1 mm is provided between the steel sheets, laser lap welding produces a good surface appearance of the weld and the welded joint strength equal to that of the cold-rolled steel sheets. This report discusses specifically how, in laser lap welding of overlapped Al-coated steel sheets, Al of the coated layer comes to enter the weld metal, also specifically how to reduce the joint strength, as well as what behaviours of Al are present when a clearance is provided between the steel sheets. When the steel sheets are closely overlapped and welded, Al becoming molten on the base metal side of the bond of the overlapped face becomes swallowed up by the bath streams of the molten pool, flowing into the molten pool, then forming the Fe–Al intermetallic compound, while not being sufficiently stirred. It is considered that when subjected to the tensile shear test, the Fe–Al intermetallic compound starts to fracture, thereby causing a partial loss of the weld metal and a reduction in the joint strength. On the other hand, when a clearance is provided between the steel sheets, it may be inferred that the fusion Al on the base metal side of the bond stays in place without flowing into the molten pool, consequently not forming the Fe–Al intermetallic compounds within the weld metal.