Influence of Mg addition and T6 heat treatment on microstructure,mechanical and tribological properties of Al-12Si-3Cu based alloy

The aim of the present study was to investigate the influence of Mg addition and T6 heat treatment on microstructure,mechanical and tribological properties of the Al-Si-Cu-Mg alloys.In this context,a series of Al-12Si-3Cu-(0.5-2.5)Mg(wt.%)alloys were produced by permanent mould casting,and then subjected to T6 treatment.Their microstructure and mechanical properties were investigated using OM,XRD,SEM,EDS along with hardness,tension,compression and Charpy impact tests.Dry sliding friction and wear properties of the alloys were studied using a ball-on-disk type tester.It was observed that the microstructure of as-cast Al-12Si-3 Cu-Mg alloys consisted of a(Al),Si,O-CuAb,0-Mg_(2)Si,0-AbMg_(8)Cu(2)Si_(6) and π-AhMg_(3)FeSi_(6) phases.T6 heat treatment gave rise to nearly spherodization of eutectic Si particles,formation of finer 0-CuAH and 0-Mg_(2)Si precipitates and elimination of Chinese script morphology of 0-Mg_(2)Si phase.The addition of Mg up to 2.5 wt.%decreased the hardness,tensile and compressive strengths,tensile elongation and impact toughness of the as-cast and T6-treated alloys and increased their friction coefficient and volume loss.T6 treatment,on the other hand,led to a significant increase in mechanical properties and wear resistance of as-cast alloys.

Influence of T6 heat treatment on A356 and A380 aluminium alloys manufactured by thixoforging combined with low superheat casting

The effects of T6 heat treatment on thixoforged A356 and A380 aluminium alloys were studied.Low superheat casting(LSC)technique was carried out to prepare proper specimens for thixoforging process.The samples were poured at 20°C above their liquidus temperatures which provided the formation of equiaxed grains instead of dendritic growth.Produced billets were reheated for varied time from 20 to 80 min and thixoforged with 50%deformation rate.After thixoforging process,the samples were T6 heat treated for both A356 and A380 alloys.The microstructural evaluation and hardness alteration of thixoforged,solution treated and aged specimens were examined comparatively by using optical microscopy,scanning electron microscopy with energy-dispersive X-ray spectroscopy and Brinell hardness equipment.T6 heat treatment provided relatively uniform microstructure with newly formed precipitates that are Mg2Si and Al2Cu for A356 and A380 billets,respectively.Accordingly,hardness after artificial aging was increased considerably and reached HB 93 for A356 and HB 120 for A380 alloys.

Effect of T6I6 treatment on dynamic mechanical behaviour of Al-Si-Mg-Cu cast alloy and impact resistance of its cast motor shell

The effect of T6I6 treatment on the dynamic mechanical and microstructure behaviour of Al-Si-Mg-Cu cast alloy was investigated using split Hopkinson pressure bar(SHPB), transmission electron microscopy(TEM), and highresolution transmission electron microscopy(HRTEM). Besides, the impact resistances of T6I6 and T6 motor shells of new energy vehicles made of Al-Si-Mg-Cu cast alloy were compared using a trolley crash test. The results indicated that the main strengthening-phases of the T6 peak-aged and T6I6 peak-aged alloy were GP zone and β″ precipitates. T6I6treatment can increase the density and size of β″ precipitates in peak-aged alloy and enhance both its tensile strength(σb)and elongation(δ). The dynamic toughness values of T6I6 samples are 50.34 MJ/m^(3) at 2000 s^(-1) and 177.34 MJ/m^(3) at 5000 s^(-1) which are 20% and 12% higher than those of T6 samples, respectively. Compared with a T6 shell, the overall deformation of T6I6 shell is more uniform during the crash test. At an impact momentum of 3.5×10;kg·m/s, the T6I6shell breaks down at 0.38 s which is 0.10 s later than the T6 shell.

Microstructures and mechanical properties of as-extruded and heat treated Mg-6Zn-1Mn-4Sn-1.5Nd alloy

The microstructures and mechanical properties of Mg-6Zn-1Mn-4Sn-1.5Nd alloy subjected to extrusion and T5 treatment were investigated using optical microscopy（OM）, X-ray diffractometer（XRD）, scanning electron microscopy（SEM）, electron back scattered diffraction（EBSD）, transmission electron microscopy（TEM）, hardness tests and uniaxial tensile tests. The results showed that the as-cast alloy consisted of α（Mg）, Mn, Mg7Zn3, Mg2 Sn and Mg Sn Nd phases. Dynamic recrystallization has completed during the extrusion process and the average grain size was 7.2 μm. After T5 treatment, the strength increased obviously, the yield strength and ultimate tensile strength of as-extruded alloy were increased by 94 and 34 MPa, respectively. Microstructure characterization revealed that the improvement of strength was determined by the high number density of β′1 rods.

Effect of pouring and cooling temperatures on microstructures and mechanical properties of as-cast and T6 treated A356 alloy

The A356 castings were fabricated using a well-developed temperature controlled permanent mold.To improve the strength and hardness of cast A356,the microstructures and mechanical properties of as-cast and T6 heat treated A356 alloy with various mold and pouring temperatures were studied.The results reveal that the undercooling is closely related to the mold and pouring temperatures.As the mold/pouring temperature changed from 258°C/680°C and 270°C/680°C to 288°C/650°C,the in-situ undercooling is 12°C,17°C and 11°C,respectively.It is observed that the Si phase changes from long continuous flake to discontinuous globular-fibrous morphology after T6 heat treatment as the mold and pouring temperature is 270°C/680°C,and the T6 heat treated specimens exhibit better mechanical properties in comparison to those as-cast ones with an increase of 162%and 102%in yield strength and elongation,which are 34.6%and 190%higher than the ASTM B108-03 a standard,respectively.As a result,the tensile fracture morphology of the as-cast A356 alloy shows quasi-cleavage fracture and the T6 heat treated A356 alloy shows ductile fracture.

Role of senescence induction in cancer treatment

Cellular senescence is a form of permanent cell cycle arrest that can be triggered by a variety of cell-intrinsic and extrinsic stimuli, including telomere shortening,DNA damage, oxidative stress, and exposure to chemotherapeutic agents and ionizing radiation. Although the induction of apoptotic cell death is a desirable outcome in cancer therapy, mutations and/or deficiencies in the apoptotic signaling pathways have been frequently identified in many human cancer types,suggesting the importance of alternative apoptosis-independent therapeutic approaches for cancer treatment. A growing body of evidence has documented that senescence induction in tumor cells is a frequent response to many anticancer modalities including cyclin-dependent kinases 4/6 small molecule inhibitor-based targeted therapeutics and T helper-1 cytokine-mediated immunotherapy. This review discusses the recent advances and clinical relevance of therapy-induced senescence in cancer treatment.

Synthesis of nano-to micrometer-sized B_(4)C particle-reinforced aluminum matrix composites via powder metallurgy and subsequent heat treatment

B4C/6061Al composites reinforced with nano-to micrometer-sized B4C particles were fabricated via powder metallurgy route consisting of spark plasma sintering(SPS)and hot extrusion and rolling(HER),followed by T6 treatment.The microstructural evolution and mechanical properties were investigated.Results showed that the status of B4C particles changed from a network after SPS to a dispersion distribution after HER.The substructured grains reached 66.5%owing to the pinning effect of nano-sized B4C,and the grain size was refined from 3.12μm to 1.56μm after HER.After T6 treatment,dispersed Mg_(2)Si precipitated phases formed,and the grain size increased to 1.87μm.Fine recrystallized grains around micro-sized B4C were smaller than those in the areas with uniform distribution of nano-sized B4C and Mg_(2)Si.The stress distributions of as-rolled and heated composites were similar,considering that the T6 heat treatment was only effective in eliminating the first internal stress.The Vickers,microhardness,and tensile strength of as-SPSed composites were greatly improved from HV 55.45,0.86 GPa,and 180 MPa to HV 77.51,1.08 GPa,and 310 MPa,respectively.Despite the precipitation strengthening,the corresponding values of as-heated composites decreased to HV 70.82,0.85 GPa,and 230 MPa owing to grain coarsening.

焊后热处理对6082-T6铝合金焊接接头组织和性能的影响

对6082-T6铝合金焊接接头进行固溶+时效和时效两种热处理,研究不同热处理制度对其组织和性能的影响。实验结果表明:未处理的6082-T6焊接接头抗拉强度为225 MPa,断裂位置位于热影响区,接头硬度最低值均在热影响区;经时效处理后的6082-T6焊接接头处强化相分布更加均匀,焊缝区组织无明显变化,熔合区和热影响区组织轻微细化,抗拉强度为264 MPa,断裂位置仍在热影响区,接头硬度最低值均在热影响区;经固溶+时效处理后的6082-T6焊接接头处重新析出细小的强化相,熔合区和热影响区组织有明显的细化,抗拉强度提高到302 MPa,断裂发生在焊缝区,硬度值明显高于未处理6082-T6焊接接头的,硬度最低值位于焊缝区。

Effects of laser shock processing,solid solution and aging,and cryogenic treatments on microstructure and thermal fatigue performance of ZCuAl_(10)Fe_(3)Mn_(2)alloy

The materials used in variable temperature conditions are required to have excellent thermal fatigue performance.The effects of laser shock processing(LSP),solid solution and aging treatment(T6),and cryogenic treatment(CT)on both microstructure and thermal fatigue performance of ZCuAl_(10)Fe_(3)Mn_(2) alloys were studied.Microstructure and crack morphology were then examined by scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS).The result showed that,after being subjected to the combination treatment of T6+CT+LSP,the optimal mechanical properties and thermal fatigue performance were obtained for the ZCuAl_(10)Fe_(3)Mn_(2) alloy with the tensile strength,hardness,and elongation of 720 MPa,300.16 HB,and 16%,respectively,and the thermal fatigue life could reach 7,100 cycles when the crack length was 0.1 mm.Moreover,the ZCuAl_(10)Fe_(3)Mn_(2) after combination treatment shows high resistance to oxidation,good adhesion between the matrix and grain boundaries,and dramatically reduced growth rate of crack.During thermal fatigue testing,under the combined action of thermal and alternating stresses,the microstructure around the sample notch oxidized and became loose and porous,which then converted to micro-cracks.Fatigue crack expanded along the grain boundary in the early stage.In the later stage,under the cyclic stress accumulation,the oxidized microstructure separated from the matrix,and the fatigue crack expanded in both intergranular and transgranular ways.The main crack was thick,and the path was meandering.

结核感染T细胞斑点试验对结核病治疗效果的监测价值

目的探讨结核感染T细胞斑点试验对结核病治疗疗效的监测意义。方法本研究采用T-SPOT.TB试剂盒,检测T细胞中γ-干扰素对结核分支杆菌特异性多肽类早期分泌性抗原靶标6-k D(ESAT-6)和培养滤液蛋白(CFP-10)的应答,对比113例结核感染者治疗前与治疗后T-SPOT.TB结果的变化,其结果根据对该试验中两种抗原的联合与各自应答来分析。结果 113例感染者在治疗后T-SPOT.TB结果转阴者有42例(37.2%)。其中,CFP-10转阴率占48.9%(P<0.001),ESAT-6转阴率占20.0%(P=0.238)。ESAT-6的斑点形成细胞(SFCs)/2.5×105外周血单核细胞(PBMCs)的平均数在治疗前和治疗后分别为18.47和16.29(P=0.16),而CFP-10的SFCs/PBMCs的平均数在治疗前和治疗后分别为22.83和15.31(P<0.01)。结论结核病治疗对于T细胞中γ-干扰素引起的ESAT-6和CFP-10抗原应答影响不同,CFP-10的定量应答才是结核病治疗的更有效监测手段。

不同剂量奥曲肽治疗重症急性胰腺炎患者的临床效果

目的探讨不同剂量奥曲肽治疗重症急性胰腺炎(severe acute pancreatitis,SAP)患者的临床效果。方法选取我院2018年10月-2022年10月收治的SAP患者154例,随机分为观察组和对照组,每组各77例。两组患者在接受乌司他丁等常规治疗的基础上,对照组患者接受0.6 mg奥曲肽静脉滴注治疗,观察组患者则接受1.2 mg奥曲肽静脉滴注治疗,均每天1次,连续治疗12 d,比较两组患者治疗12 d时的治疗总有效比例、不良反应发生比例、临床症状消失时间及血淀粉酶复常时间,同时比较两组患者治疗前后血清炎性因子C反应蛋白(CRP)、肿瘤坏死因子-α(TNF-α)、白细胞介素-6(IL-6)、T淋巴细胞水平及急性生理与慢性健康评分(APACHEⅡ评分)、改良CT严重指数(MCTSI)评分的变化。结果观察组患者治疗总有效比例明显高于对照组(χ2=5.140,P<0.05);治疗12 d时,观察组患者发热、腹胀及腹痛症状消失时间及血淀粉酶复常时间明显少于对照组(t=14.703~22.543,P<0.01);观察组患者治疗前后CRP、TNF-α、IL-6、CD8^(+)、CD4^(+)水平及CD4^(+)/CD8^(+)比值的差值明显高于对照组(t=4.706~17.498,P<0.05);观察组治疗前后APACHEⅡ及MCTSI评分差值均显著高于对照组(t=15.629、19.676,P<0.01);两组不良反应发生比例比较差异无显著性(P>0.05)。结论大剂量奥曲肽可有效提高SAP患者的疗效,增强患者机体免疫功能,减轻患者的炎症反应水平,且安全性较高,值得临床推广应用。

T-SPOT.TB在结核性脊柱炎疗效评价中的作用

目的探讨结核感染T细胞试验(T-SPOT.TB)中两种抗原ESAT-6及CFP-10在评价结核性脊柱炎治疗效果中的价值.方法回顾性分析2013年1月至2016年1月就诊于昆明医科大学第一附属医院、T-SPOT.TB(+),初治且明确诊断为结核性脊柱炎并随访成功共29例.应用Wilcoxon秩合检验及χ2检验分析ESAT-6及CFP-10在结核性脊柱炎疗效过程中变化.并绘制ESR、CRP、VAS与ESAT-6及CFP-10的散点图进行线性回归分析.结果 ESAT-6及CFP-10治疗前的斑点计数分别与治疗后6个月、12个月及治愈后的斑点计数比较,治疗6个月时,斑点计数下降无统计学意义,治疗12个月及治愈后斑点计数较治疗前明显下降,P<0.05,差异有统计学意义.CFP-10治疗前的阳性结果分别与治疗后3次随访阳性结果进行χ2检验,治疗前、治疗后6个月、12个月及治愈后阳性率分别为86.20%、86.20%、75.86%、58.62%,P<0.05,差异有统计学意义.ESAT-6仅与VAS呈线性相关,而CFP-10与VAS、ESR均呈线性相关关系,但是相关性均较弱.结论 ESAT-6及CFP-10的斑点计数下降提示治疗有效,且CFP-10可能成为评价治疗效果的指标之一.

Semi-solid near-net shape rheocasting of heat treatable wrought aluminum alloys

Flexibility of the CSIR-RCS, induction stirring with simultaneous air cooling process, in combination with high pressure die casting is successfully demonstrated by semi-solid rheocasting of plates performed on commercial 2024, 6082 and 7075 wrought aluminum alloys. Tensile properties were measured for the above mentioned rheocast wrought aluminum alloys in the T6 condition. The results showed that tensile properties were close to or even in some cases exceeded the minimum specifications. The yield strength and elongation of rheocast 2024-T6 exceeded the minimum requirements of the wrought alloy in the T6 condition but the ultimate tensile strength achieved only 90% of the specification because the Mg content of the starting alloy was below the commercial alloy specification. The strengths of rheocast 6082-T6 exceeded all of the wrought alloy T6 strength targets but the elongation only managed 36% of the required minimum due to porosity, caused by incipient melting during solution heat treatment, and the presence of fine intermetallie needles in the eutectic. The yield strength of rheocast 7075 exceeded the required one and the ultimate tensile strength also managed 97% of the specification; while the elongation only reached 46% of the minimum requirement also due to incipient melting porosity caused during the solution heat treatment process.

Influence of Cu content on microstructure and mechanical properties of thixoformed Al-Si-Cu-Mg alloys

The effects of Cu content on the microstructure and mechanical properties of thixoformed Al-6Si-xCu-0.3Mg(x= 3,4,5and 6,mass fraction,%) alloys were studied.The samples were thixoformed at 50%liquid content and several of the samples were treated with the T6 heat treatment.The samples were then examined by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray(EDX) spectroscopy and X-ray diffraction(XRD) analysis,as well as hardness and tensile tests.The results show that the cooling slope casting and thixoforming process promote the formation of very fine and well distributed intermetallic compounds in the aluminium matrix and the mechanical properties of the alloys increase considerably compared with the permanent mould casting.The results also reveal that as the Cu content in the alloy increases,the hardness and tensile strength of the thixoformed alloys also increase.The ultimate tensile strength,yield strength and elongation to fracture of the thixoformed heat-treated Al-6Si-3Cu-0.3Mg alloy are 298 MPa,201 MPa and 4.5%,respectively,whereas the values of the thixoformed heat-treated alloy with high Cu content(6%) are 361 MPa,274 MPa and 1.1%,respectively.The fracture of the thixoformed Al-6Si-3Cu-0.3Mg alloy shows a dimple rupture,whereas in the alloy that contains the highest Cu content(6%),a cleavage fracture is observed.

Effects of minor Y,Zr and Er addition on microstructure and properties of Al-5Cu-0.4Mn alloy

The effect of different contents of Y, Zr and Er on microstructure and properties of Al-5 Cu-0.4 Mn alloy was investigated. T6 heat treatment, OM, SEM and EDS methods were applied to the alloy. The results showed that fluidity and elongation of alloy adding Y, Zr and Er were improved, while with the increase of addition amounts, θ phase increased and grains were trended to grow up gradually. The Al-5 Cu-0.4 Mn alloy presented the maxed style of ductile and brittle fracture. After T6 heat treatment, the precipitation amounts of θ phase decreased dramatically and tensile strength and hardness significantly increased. Especially when addition contents were among 0.1-0.3 wt.%, tensile strength and hardness of heat-treated alloy increased greatly, almost doubled as that of the as-cast state. The tensile strength reached its maximum of 378.43 MPa when the addition amount was 0.3 wt.%. With the further increase of addition amounts, the elongation deteriorated and the proportion of ductile fracture reduced due to the limited dispersion strengthening effect of θ phase and Al_8Cu_4 Er. It demonstrated that addition of 0.1-0.3 wt.% Y, Zr and Er would generate positive effects and influences on Al-5 Cu-0.4 Mn alloy, which is significant for optimizing components and improving properties of Al-5 Cu-0.4 Mn alloy.

T-SPOT.TB在活动性肺结核治疗效果的监测

目的探讨结核感染T细胞斑点试验(T-SPOT.TB)对肺结核治疗效果的监测意义。方法采用TSPOT.TB试剂盒,检测其抗原ESAT-6和CFP-10的应答,对比79例活动性肺结核患者治疗前与治疗2月末及治疗结束时ESAT-6和CFP-10应答结果的变化。结果 79例活动性肺结核患者,ESAT-6和CFP-10应答的斑点数在治疗2月末和治疗结束时较治疗初均有明显下降,与治疗初比较,差异均有统计学意义(P <0.05)。ESAT-6和CFP-10在治疗2月末和治疗结束时阴性率较治疗初有上升,与治疗初的阴性率比较,差异无统计学意义(P> 0.05);全部患者T-SPOT.TB转阴率为3.8%。治疗2月末与治疗结束时ESAT-6应答变化,差异有统计学意义(χ^(2)=4.635,P=0.031 <0.05);治疗2月末与治疗结束时CFP-10应答变化,差异无统计学意义(χ^(2)=1.272,P=0.259> 0.05)。结论 T-SPOT.TB治疗前后ESAT-6、CFP-10应答变化有明显差异,对肺结核治疗效果评价有一定作用,但不能利用其转阴率作为肺结核治疗停药指标。

Microstructural evolution and mechanical properties of thixoformed A319 alloys containing variable amounts of magnesium

The effects of Mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to the T6 heat treatment. The samples were then examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as tensile tests. The results showed that magnesium was able to refine the eutectic silicon in the samples. It was also observed that a compact Al9FeMg3Si5 phase was formed when the magnesium content was 1.0% and 1.5%. The results also revealed that as the magnesium content in the alloy increases, the tensile strengths of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed A319 heat treated alloy were 298 MPa, 201 MPa and 4.5%, respectively, whereas the values of the thixoformed heat treated alloy with 1.5% Mg content were 325 MPa, 251 MPa and 1.4%, respectively. Thixoformed A319 alloy showed a dimple fracture behaviour, while thixoformed A319 alloys with 1.5% Mg showed a mixed mode fracture behaviour, where dimple and cleavage ruptures were seen on the fracture surface of the samples.

Effects of Zr additions on structure and tensile properties of an Al-4.5Cu-0.3Mg-0.05Ti(wt.%) alloy

The effects of different Zr additions(0.05wt.%-0.5wt.%)on the structure and tensile properties of an Al-4.5Cu-0.3Mg-0.05Ti(wt.%)alloy solidified under a high cooling rate(18℃·s^(-1)),in as-cast and T6 heat-treated conditions were studied.The as-cast structure of the alloy consists of equiaxed grains ofα-Al with an average size of 64μm which is unaffected by the Zr additions,indicating the ineffectiveness of Zr in the grain refinement of the alloy.Scanning electron microscopy,along with X-ray diffraction analysis revealed the presence of elongatedθ-Al2Cu at the grain boundaries;in addition,coarse Al3Zr particles exist in the intergranular regions of the 0.5wt.%Zr-containing alloy.After the T6 heat treatment,the elongatedθparticles were fragmented;however,the coarse Al3Zr particles remained unchanged in the microstructure.Also,the formation of fineβ’-Al3Zr andθ’’-Al3Cu/θ’-Al2Cu phases during T6 heat treatment was revealed by transmission electron microscopy.The results of the tensile tests showed that the Zr additions increase the strength of the alloy in both as-cast and T6 heat-treated conditions,but reduce its elongation,especially with 0.5wt.%Zr addition.The 0.3wt.%Zr-added alloy in the T6 heat-treated condition has the highest quality index value(249 MPa).Fractography of the fracture surfaces of the alloys revealed ductile fracture mode including dimples and cracked intermetallic phases in both conditions.

T淋巴细胞亚群检测在结核病诊治中的应用探讨

目的:观察分析T淋巴细胞亚群检测在结核病诊治中的应用价值。方法:选取本院2019年1月~2020年1月收治的108例肺结核患者一般资料作为实验组,再选取同期我院接收的108例健康体检者一般资料作为对照组。采用统计学分析两组研究对象的T淋巴细胞亚群(CD3、CD4、CD8、CD4/CD8)表达水平、外周血白细胞介素-1、外周血白细胞介素-6以及肺结核患者T淋巴细胞亚群检测结果与性别、年龄之间的关系。结果:肺结核患者T淋巴细胞亚群检测结果与性别比较差异无统计学意义(P>0.05),肺结核患者T淋巴细胞亚群检测结果与年龄比较差异有统计学意义(P<0.05);实验组CD3、CD4、CD4/CD8等T淋巴细胞亚群表达水平明显低于对照组,实验组CD8表达水平明显高于对照组,差异比较有统计学意义(P<0.05),实验组外周血白细胞介素-1、外周血白细胞介素-6水平明显高于对照组,差异比较有统计学意义(P<0.05)。结论:外周血白细胞介素-1、外周血白细胞介素-6、T淋巴细胞是结核病患者细胞免疫的重要组成部分,检测外周血白细胞介素-1、外周血白细胞介素-6、T淋巴细胞可能为肺结核提供诊断依据,与此同时在肺结核患者的治疗和预后具有显著意义;结核病患者T淋巴细胞免疫功能下降,有可能是导致结核病患者病情持续加重的原因。

Microstructure and mechanical properties of 600 MPa grade ultra-high strength aluminum alloy fabricated by wire-arc additive manufacturing

The utilization of wire-arc additive manufacturing(WAAM)technology for the preparation of Al-Zn-Mg-Cu aluminum alloy has made some progress in recent years.However,the challenge still remains to achieve ultra-high strength(600 MPa)in WAAM.In this study,the crack-free Al-Zn-Mg-Cu-Sc thin-wall component with ultra-high strength was successfully fabricated by the cold metal transfer(CMT)pro-cess using a self-prepared 7B55-Sc filler wire.The microstructures of both as-deposited and T6 heat-treated samples were all composed of fine equiaxed grains with an average size of about 6.0μm.The primary Al_(3)(Sc,Zr)particles acted as heterogeneous nuclei to promote the formation of equiaxed grains and refine the microstructures during the solidification process.A large amount of continuous eutectic structures rich in Al,Zn,Mg,and Cu elements formed along the grain boundaries under the as-deposited condition,and the precipitated second phases within the grains mainly included the equilibriumηphase,metastableηphase and large-sized T phase.After T6 heat treatment,the majority of the second phases originally distributed within grains and along grain boundaries were dissolved into the Al matrix,and a large amount of fine GP zones,ηphase and secondary Al_(3)(Sc,Zr)particles were precipitated within the grains during the aging process.The tensile strength reached a recorded level of 618 MPa in the hori-zontal direction after T6 heat treatment,which was considered a breakthrough for the manufacturing of 600 MPa grade aluminum alloy by WAAM.