选区激光熔化铝合金制备研究现状

选区激光熔化（selective laser melting,SLM）技术因具有可定制化、加工周期短及精度高等特点,在工业生产中得到广泛应用。本文对选区激光熔化技术及其在铝合金及铝基复合材料制备的研究现状进行了综合性论述。通过论述选区激光熔化特性引出选区激光熔化打印铝合金的优势。介绍了适用于选区激光熔化技术的铸造Al?Si系合金,结合扫描策略和工艺参数优化,探究了选区激光熔化铝硅合金的微观结构、相组成和力学性能变化规律。讨论了选区激光熔化微/纳米陶瓷强化铝基复合材料的研究现状,分析与总结了添加强化颗粒对组织结构、相对密度、润湿性及相应力学性能的强化机理。总结了工业界与学术界关注的新型高强度铝合金材料的开发及其选区激光熔化的制备,重点论述了新型铝合金的固溶强化和析出相强化机理,并分析了对相对密度和力学性能的影响因素。最后对选区激光熔化铝合金发展趋势及现阶段存在的问题进行了展望。     

激光熔化沉积AlxCoCrFeNiMn组织与性能研究

为了探讨Al元素对Al_xCoCrFeNiMn (x=0,0.2,0.4,0.6,0.8,1.0)高熵合金(HEAs)相组成、显微组织、力学性能的影响，并得到具备高强度和高塑韧性的高熵合金成分。选用激光熔化沉积技术(LMD)制备Al_xCoCrFeNiMn HEAs块体，并对其进行宏微观形貌观察、相组成表征和力学性能测试。研究发现，随着x从0增加到1.0，晶粒沿〈100〉方向的择优取向性逐渐消失；显微组织由粗大的树枝晶到柱状晶再到类似于魏氏组织的层片状结构，并且晶粒逐渐细化；相组成由面心立方(fcc)向体心立方(bcc)+fcc结构转变；硬度、强度和耐磨性逐渐提高，Al_0.8合金的硬度为HV 292，抗拉强度为774.5 MPa，磨损率降低了53.5%；延伸率呈现先增加后降低的趋势，Al_0.4合金的延伸率最高为51.0%；随着Al含量进一步增加，合金延伸率出现恶化，Al_0.8合金的延伸率仅为5%。经综合对比，Al_0.6合金抗拉强度提高了41.7%，硬度提高了2...     

选区激光熔化CoCrFeNi-X高熵合金的研究进展

CoCrFeNi高熵合金因其单一稳定的面心立方固溶体结构,具有优异的塑性变形能力和较高的屈服强度,已成为众多追求高韧性制件研究的热门体系之一。同时选区激光熔化技术因其成形尺寸灵活和超快加热冷却速率,具备传统制备方式不可比拟的优势。通过梳理近些年选区激光熔化技术成功制备出的CoCrFeNiX高熵合金体系,首先针对8种不同合金体系的相结构和组织形貌,分析了组织结构对力学性能的影响;其次针对3种采用不同工艺参数制备的CoCrFeNi-X高熵合金成形件,分析制备工艺对成形密度及力学性能的影响;最后就合金成分设计对CoCrFeNi-Alx、CoCrFeNi-Mn两种主流合金体系做了详细研究现状分析。期望对采用选区激光熔化技术制备CoCrFeNi-X体系高熵合金的实验研究和工业应用提供一定的理论指导。     

激光增材制造技术制备高熵合金研究进展

介绍了激光增材制造高熵合金的工艺方法,从成形工艺、合金元素含量（摩尔分数）、热处理工艺和增强相添加等几个方面综述了国内外激光增材制造高熵合金的研究进展,分析了激光熔化沉积和选区激光熔化成形两种主要激光增材制造技术,以及两种技术制备高熵合金的微观结构和力学性能,指出了高熵合金激光增材制造技术的发展趋势及存在的主要问题,并提出了改进措施。     

激光熔化沉积Cu-Fe合金的液相分离组织及力学性能研究

难混溶合金由于亚稳难混溶间隙的存在，在制备过程中极易产生偏析甚至分层现象，严重影响材料的使用性能。激光熔化沉积小熔池无宏观偏析的特点，为制备均质难混溶合金提供了潜在途径。本文选取典型难混溶Cu-Fe合金作为研究对象，采用激光熔化沉积制备了薄壁状Cu35Fe65难混溶合金，研究了合金的物相组成、微观组织形貌与力学性能。结果表明：合金由体心立方（bcc）结构的α-Fe相与面心立方（fcc）结构的Cu相组成；合金呈现典型的液相分离形貌，由网络状Cu相与块状α-Fe相构成，α-Fe相平均直径为8 μm；合金屈服强度为397 MPa，抗拉强度为484 MPa，延伸率为16.5%，断裂方式主要为韧性断裂；合金的导电率为19% IACS，较高的α-Fe相体积分数可能是影响合金电阻率的主要因素。本研究表明，激光熔化沉积技术有望成为高性能难混溶合金的有效制备方式。     

重熔工艺对激光选区熔化Ti-1Al-8V-5Fe合金组织及性能的影响

为消除传统铸造加工生产的Ti-1Al-8V-5Fe(Ti185)合金中的β斑,采用激光选区熔化技术使大粒径Ti185合金粉末成形,通过重熔工艺对激光选区熔化Ti185合金进行优化,并对重熔前后成形样品的顶部、中部、底部三个位置进行了组织和力学性能分析。结果表明,激光选区熔化成形的Ti185样品中存在宏观裂纹,而重熔工艺能有效抑制该裂纹的产生。激光选区熔化和重熔优化成形样品的显微组织均由等轴β相组成,且等轴晶粒的内部存在亚晶结构。通过重熔优化后的激光选区熔化成形样品的最高抗压强度为2 127±120 MPa,断裂应变为21%±5%,压缩性能相比重熔前的样品有所下降。     

选区激光熔化 GH3625 显微组织及拉伸性能分析

激光选区熔化技术是增材制造技术的一种,该技术自诞生以来在金属样件制备过程中发挥越来越重要的作用。但是运用该技术制备成型件的组织研究尚未明确,本文以GH3625高温合金为例,研究选区激光熔化成型件组织特点及拉伸性能。结果表明,选区激光熔化成型件组织主要为胞状晶,选区激光熔化微熔池中,晶粒生长方向在同一个区域中呈现出典型的细小柱状晶(亚晶)和近似六边形的胞状晶。拉伸实验结果表明选区激光熔化成型试样具有良好的拉伸性能。     

Ti6Al4V在不同成形工艺下的数值分析及组织性能

基于选区激光熔化和熔模铸造不同工艺成形原理,采用有限元数值分析软件以及Fortran语言编写的DLUX子程序进行有限元仿真模拟,研究试样在不同成形方式下冷却速度与温度场动态过程.采用选区激光熔化和熔模铸造制备不同的Ti6Al4V钛合金试样,探寻冷却过程对微观组织、晶粒结构与力学性能内部联系.结果表明:选区激光熔化(se...     

选区激光熔化成形GH4169合金研究现状

介绍了选区激光熔化成形GH4169合金存在的球化、孔洞等常见缺陷的形成机理及工艺控制现状,重点分析了激光功率、扫描速率、铺粉厚度等工艺参数对选区激光熔化成形GH4169合金成形件组织性能的影响规律,以及热处理、颗粒增强等组织性能调控手段对选区激光熔化成形GH4169合金组织性能影响。从工艺控制、材料强化设计等方面对选区激光熔化成形GH4169合金进行展望,认为利用选区激光熔化成形技术开展颗粒增强GH4169复合材料的设计与成形是进一步提升选区激光熔化成形GH4169合金性能的有效途径。     

多主元高熵合金的强韧化

高熵合金是近年来出现的一种全新的合金设计理念,该类合金通常由4种以上的合金元素以等原子比或近等原子构成,各元素间没有"溶质"与"溶剂"的区分,原子间的交互作用强烈,使其具有很多特殊的物理、化学及力学性能.但与传统合金类似,高熵合金也存在强度与塑性不容易匹配的难题——fcc结构高熵合金的塑性较好而强度不足,bcc结构高熵...     

Effect of Ni on Microstructure and Mechanical Properties of CrMnFeCoNi High Entropy Alloy

The effect of Ni content on microstructure and mechanical properties of the CrMnFeCoNi high entropy alloy (HEA) has been studied. The Ni content varied from 0 to 20 at% in the composition (CrMnFeMn)_100?xNi_x, where x?=?0, 2.5, 5, 10, 15, and 20 at%. The alloys were synthesized by vacuum arc melting and the microstructure as well as hardness of the as-cast alloys were studied. Alloys with low Ni content (x?≤?2.5%) consists of a two-phase microstructure of dendritic and inter-dendritic regions with fcc (matrix) and tetragonal (sigma) crystal structure, respectively. When the Ni content is 5 at%, two-phase structure with fcc (matrix) and bcc (secondary phase) is observed, with the addition of Mn-rich inclusions that are present in the entire matrix. Alloys with higher Ni content (x?≥?10, at%) exhibit a single phase of fcc structure. Hardness of the HEAs decreases from 320 to 120 Hv with increase in Ni content, and the high hardness of these alloys with low Ni content is due to the mixture of both fcc and hard tetragonal (sigma) phases.

     

Formation and Stability of Equiatomic and Nonequiatomic Nanocrystalline CuNiCoZnAlTi High-Entropy Alloys by Mechanical Alloying

Nanocrystalline equiatomic high-entropy alloys (HEAs) have been synthesized by mechanical alloying in the Cu-Ni-Co-Zn-Al-Ti system from the binary CuNi alloy to the hexanary CuNiCoZnAlTi alloy. An attempt also has been made to find the influence of nonequiatomic compositions on the HEA formation by varying the Cu content up to 50 at. pct (Cu _x NiCoZnAlTi; x = 0, 8.33, 33.33, 49.98 at. pct). The phase formation and stability of mechanically alloyed powder at an elevated temperature (1073 K [800 °C] for 1 hour) were studied. The nanocrystalline equiatomic Cu-Ni-Co-Zn-Al-Ti alloys have a face-centered cubic (fcc) structure up to quinary compositions and have a body-centered cubic (bcc) structure in a hexanary alloy. In nonequiatomic alloys, bcc is the dominating phase in the alloys containing 0 and 8.33 at. pct of Cu, and the fcc phase was observed in alloys with 33.33 and 49.98 at. pct of Cu. The Vicker’s bulk hardness and compressive strength of the equiatomic nanocrystalline hexanary CuNiCoZnAlTi HEA after hot isostatic pressing is 8.79 GPa, and the compressive strength is 2.76 GPa. The hardness of these HEAs is higher than most commercial hard facing alloys (e.g., Stellite, which is 4.94 GPa).     

Synthesis of Al0.5CoCrCuFeNi and Al0.5CoCrFeMnNi High-Entropy Alloys by Laser Melting

High-entropy alloys (HEAs) are a blend of 5+ metallic elements that can form solid solution disordered structures. Two HEAs were synthesized using laser melting in an argon atmosphere. The relatively well-studied Al_0.5CoCrCuFeNi alloy was first produced to establish the feasibility of laser melting. Manganese was then substituted for copper to potentially lower both cost and density, producing a novel Al_0.5CoCrFeMnNi alloy system. These samples were analyzed with XRD, SEM, EDS, and Vickers microhardness to determine the effects of the manganese substitution, as well as the effects of laser melting in comparison to the more traditional arc melting.     

难熔高熵合金:制备方法与性能综述

从加工方法、微观结构以及各类性能三方面介绍了难熔高熵合金(Refractory high-entropy alloys,RHEAs),最后对难熔高熵合金的发展和未来进行了展望。以MoNbTaVW为代表的难熔高熵合金在高温下表现出优于传统镍基高温合金的压缩屈服强度,且屈服强度随温度的变化更加缓慢,高温力学性能优异;以MoNbTaVW、MoNbTaTiZr、HfNbTiZr等为代表的难熔高熵合金,与商用高温合金、难熔金属、难熔合金以及工具钢相比,展现出更优的耐磨性能。以W₃₈Ta₃₆Cr₁₅V₁₁合金为代表的难熔高熵合金在辐照后,除了析出小颗粒第二相外,不存在位错环缺陷结构,抗辐照性能优异。提出了难熔高熵合金未来发展的两大方向:建立高通量的实验和计算方法继续探索更多的难熔高熵合金组成和结构模型;探索多场耦合环境下难熔高熵合金的服役行为。      

Anisotropy of mechanical properties of products manufactured using selective laser melting of powdered materials

Causes of the appearance of anisotropy of properties in products manufactured according to the technology of selective laser melting of metallic powder materials are investigated. The results of an evaluation of mechanical properties of the samples made of Ti–6Al–4V and VT6 titanium-based alloys and Inconel 718 refractory nickel alloy in various directions are presented. The dependence of their mechanical properties on the orientation of billets relative to the working platform of the installation is presented. An analysis of microslices of the Ti–6Al–4V alloy showed that the direction of the granular structure for a rectangular sample corresponds to the growth direction, while, when manufacturing thin elements of a net construction, other thermal processes flow due to their smaller cross section, which affects the crystallization conditions and microstructure being formed. Grain directions and shapes change depending on the slope angle of the element of the net structure.     

Microstructure,Corrosion Behaviour and Microhardness of Non-equiatomic Fe 1.5 CoNiCrCu x (0.5 ≤ x ≤ 2.0) High-Entropy Alloys

The microstructure, electrochemical corrosion behaviour and microhardness of Fe1.5CoNiCrCux (x = 0.5, 1.0, 1.5 and 2.0) high-entropy alloys (HEAs) were investigated by X-ray diffraction (XRD), scanning electron microscopy and an electrochemical workstation. The XRD spectra of Fe1.5CoNiCrCux HEAs confirmed the face-centred cubic solid solution structure and that all specimens consisted of an fcc matrix and a Cu-rich fcc phase. The results of electrochemical corrosion tests showed that Fe1.5CoNiCrCu0.5 HEAs exhibited low corrosion rates owing to their high corrosion potential and low corrosion current density. The major types of corrosion for Fe1.5CoNiCrCux HEAs belong to localised corrosion and pitting, which is attributed to Cu-rich and Cr-depleted phases in the interdendritic region. The microhardness of Fe1.5CoNiCrCux HEAs increases from 142 HV for alloys with x = 0.5 to 190 HV for alloys with x = 2.0.     

返回次数对镍基K4169合金组织及性能的影响

采用50%返回料+50%新料的新工艺熔炼镍基K4169合金,进行了4次返回料的熔炼试验。采用金相显微镜及扫描电镜对新料合金及返回料合金的微观形貌进行了观察,用直读光谱仪对不同返回次数的合金进行了化学成分分析、对其力学和持久性能进行测试,研究了返回料熔炼对合金化学成分、微观组织及力学性能的影响。结果表明:随返回次数增加,化学成分无明显变化,合金的气体含量略呈下降趋势且总含量低于40×10-6,返回料冶炼过程中可不添加B和Zr。K4169合金凝固组织为典型枝晶结构,返回料对K4169合金的铸态枝晶组织没有明显影响。MC型碳化物及Laves相在热处理过程中部分分解,析出针片状δ相,在所有元素中,Nb的偏析最为严重,通过适当延长固溶处理时间可提高元素Nb的分布均匀性和抑制δ相的生成。返回料合金的室温拉伸强度及屈服强度随返回次数增加略有增加,合金的持久寿命较新料合金略有降低,但均明显超过现有技术标准规定的要求。熔炼的返回料合金具有良好的中温塑性,总体上与新料的质量水平相当。返回料合金的铸造性能与新料相当,可以代替新料用于铸件生产。     

High-entropy alloys fabricated via powder metallurgy. A critical review

High-entropy alloys (HEAs) have attracted a great deal of interest over the last 14 years. One reason for this level of interest is related to these alloys breaking the alloying principles that have been applied for many centuries. Thus, HEAs usually possess a single phase (contrary to expectations according to the composition of the alloy) and exhibit a high level of performance in different properties related to many developing areas in industry. Despite this significant interest, most HEAs have been developed via ingot metallurgy. More recently, powder metallurgy (PM) has appeared as an interesting alternative for further developing this family of alloys to possibly widen the field of nanostructures in HEAs and improve some capabilities of these alloys. In this paper, PM methods applied to HEAs are reviewed, and some possible ways to develop the use of powders as raw materials are introduced.