机械合金化和真空热压烧结FeCoCrNiMn高熵合金的显微组织和力学性能（英文）

采用机械合金化和热压烧结制备FeCoCrNiMn高熵合金。结果表明,采用机械合金化得到纳米晶合金粉末,粉末相结构由面心立方结构(FCC)相以及少量的体心立方结构(BCC)相和非晶相组成。热压烧结后,合金中BCC相基本消失,同时伴随着σ相和M23C6相的析出;烧结温度的升高导致析出相颗粒明显长大。随着热压烧结温度从700℃升高到1000℃,合金塑性应变从4.4%增加到38.2%,而屈服强度从1682 MPa下降到774 MPa。经800℃和900℃烧结1 h的FeCoCrNiMn高熵合金具有较好的综合力学性能。     

粉末冶金FeCoNiCu0.4Al0.4高熵合金的热处理组织与性能

采用机械合金化(MA)与放电等离子烧结(SPS)相结合的方法制备出FeCoNiCu0.4Al0.4高熵合金,研究不同热处理温度对合金显微组织与力学性能的影响规律。结果表明:机械合金化后,FeCoNiCu0.4Al0.4高熵合金形成了单相的FCC固溶体,经1100℃SPS烧结后的块体组织仍为单相FCC结构,其压缩屈服强度、塑性应变和显微硬度分别为1165.1 MPa、45.2%和356.9 HV。经过热处理后,合金组织中生成了新的BCC相,且BCC相的含量随热处理温度的升高先增多后减少,500、600和700℃热处理后BCC相的含量分别为7%、30%和21%(体积分数)。退火态FeCoNiCu0.4Al0.4高熵合金的屈服强度随热处理温度的升高先升高后降低。当BCC相含量增多时,材料的屈服强度和硬度相应地提高,而塑性却显著降低。     

放电等离子烧结制备低密度AlTiCrNiCu高熵合金及其组织性能研究

采用机械合金化和放电等离子烧结工艺制备了低密度AlTiCrNiCu高熵合金材料,重点研究了球磨时间对各元素粉末的合金化过程及烧结温度(950 ~ 1050 ℃)对高熵合金组织及力学性能的影响。结果表明：高熵合金粉末为单相BCC结构,随着球磨时间的增加,粉末粒径先变大后变小,其最终平均粒径大约为20 μm。高熵合金块体材料的相结构为BCC1(基体相)+BCC2(富Cr相)+FCC(富Cu相),密度为6.22 ~ 6.30 g/cm_³。烧结温度的升高,有利于高熵合金粉末的冶金结合,促进了高熵合金块材料的致密化。当烧结温度为1050 ℃时,AlTiCrNiCu高熵合金具有良好的综合力学性能,其屈服强度、压缩强度、塑性和显微硬度分别为1410 MPa,2000 MPa,9.13%和524 HV。分析认为高的烧结温度为各元素原子间的充分扩散提供了足够的能量。然而,TEM分析表明,高的烧结温度也促进了弥散的FCC富Cu相在晶界的聚集长大。     

冷轧和退火对Ni40(FeCoCrAl)60高熵合金组织与性能的影响

研究了高温退火和二次退火对冷轧后Ni₄₀(FeCoCrAl)₆₀高熵合金组织和性能的影响。结果表明,铸态合金由FCC+BCC双相组成。冷轧并再结晶后,合金保持稳定的相结构,FCC相由树枝晶转变为等轴晶,BCC相位于FCC相之间和FCC相之内。铸态合金的屈服强度和抗拉强度分别为450 MPa和870 MPa,伸长率为40%。室温冷轧后合金强度显著升高,屈服强度和抗拉强度分别是铸态合金的2.9倍和1.7倍,伸长率降至4%。再结晶退火使屈服强度和抗拉强度分别降为590 MPa和820 MPa,伸长率为12%。     

粉末冶金制备Fe_(28)Ni_(28)Mn_(28)Cr_8Cu_8与Fe_(28)Ni_(28)Mn_(28)Cr_8Al_8高熵合金的微观组织与力学性能

采用"机械合金化(MA)+放电等离子烧结(SPS)"的方法制备出Fe_(28)Ni_(28)Mn_(28)Cr_8Cu_8和Fe_(28)Ni_(28)Mn_(28)Cr_8Al_8两种高熵合金块体,并研究其微观组织和力学性能。结果表明:两种高熵合金均在机械合金化后形成了FCC+BCC相的合金粉末。与Fe_(28)Ni_(28)Mn_(28)Cr_8Cu_8合金相比较,当Cu元素被Al元素取代之后,Fe_(28)Ni_(28)Mn_(28)Cr_8Al_8高熵合金粉末中BCC结构的固溶体相含量明显增加。经SPS烧结后,Fe_(28)Ni_(28)Mn_(28)Cr_8Cu_8由单相FCC和少量富Cr相组成;Fe_(28)Ni_(28)Mn_(28)Cr_8Al_8则形成双相FCC结构。同时,两种高熵合金在室温下均表现出良好的压缩性能;相较于Fe_(28)Ni_(28)Mn_(28)Cr_8Cu_8,Fe_(28)Ni_(28)Mn_(28)Cr_8Al_8的屈服强度由716 MPa提高到1181 MPa,抗压强度由1908 MPa提高为2111 MPa,硬度也由267 HV上升到482 HV,但塑性却由38.6%降至26.1%。     

放电等离子烧结MoNbTaW难熔高熵合金

以纯金属元素粉末为原料,采用放电等离子烧结工艺制备了MoNbTaW难熔高熵合金,研究了烧结温度和保温时间等工艺参数对MoNbTaW难熔高熵合金的物相、晶体结构、烧结行为和力学性能的影响。结果表明,在烧结温度1800℃和保温5min即可形成BCC单相高熵合金;烧结温度是影响MoNbTaW难熔高熵合金致密度、晶粒尺寸和力学性能的主要因素;随着烧结温度的升高,合金的晶粒尺寸增大,致密度、硬度和和屈服强度均增高;烧结温度为2000℃时合金的致密度可达99.8%,化学成分无偏析,屈服强度为1314±14MPa,断裂韧性为(5～6)MPa.m_1/2,其断裂模式为解理断裂。     

Ti对单相FCC的CoCrNi体系中/高熵合金组织与性能的影响

在CoCrNi三元、CoCrFeNi四元和Al_0.3CoCrFeNi五元合金中分别添加0.1～0.5(摩尔比)Ti，通过真空电弧炉制备出高硬度和高压缩强度的中/高熵CoCrNiTi_x、CoCrFeNiTi_x和Al_0.3CoCrFeNiTi_x合金棒材。Ti添加量为0.1的合金棒材(以下简称Ti_0.1合金，其余合金作相同处理)均保持单相FCC结构；Ti_0.3合金均出现少量的新相(η或R);CoCrNiTi_0.5合金由FCC+BCC+η+σ相组成，Al_0.3CoCrFeNiTi_0.5合金由FCC+BCC+R+B₂相组成，且二者微观组织均呈“花朵”状；而CoCrFeNiTi_0.5合金则由FCC+Laves+R+σ相组成，为树枝晶状结构。随着Ti含量的增加，三种体系合金的硬度均逐渐提高，且提高幅度按CoCrNiTi_x     

TiC增强AlCr_2FeNi_2Cu_(1.6)高熵合金基复合材料组织与性能

采用真空电弧炉制备了(TiC)_x/AlCr_2FeNi_2Cu_(1.6)高熵合金复合材料,研究了TiC含量对AlCr_2FeNi_2Cu_(1.6)高熵合金微观组织与力学性能的影响。结果表明,(TiC)_x/AlCr_2FeNi_2Cu_(1.6)高熵合金复合材料由FCC相和BCC相组成,TiC粉末的加入并未使高熵合金的物相结构发生转变,但随着TiC的添加,合金中出现了TiC的衍射峰。高熵合金中FCC相富集了Cu、Al、Ni元素,BCC相富集了Fe、Cr元素。添加TiC后,合金中出现了含有TiC的Al、Ni、Cu新相,且使高熵合金的压缩屈服强度和抗压强度先增加后减小。当TiC含量为7.5%时,合金的屈服强度和抗压强度相对较高,压缩应变骤降到8.32%。     

FeCrNi(AlTi)x双相中熵合金的组织结构及其力学性能

采用真空悬浮感应熔炼法制备了FeCrNi(AlTi)_x(x=0、0.2、0.34和0.49)双相中熵合金,研究Al和Ti含量变化以及均匀热化处理对合金微观结构和力学性能的影响。结果表明：随着Al、Ti含量的增加,合金的相结构由FCC单相结构转变成FCC和BCC的双相结构,且随着Al、Ti含量的增加,BCC相的体积分数明显增加,合金的压缩屈服强度和硬度显著增加。均匀化热处理之后,FeCrNi(AlTi)_0.2合金的屈服强度和极限抗拉强度分别达到了519和852 MPa,伸长率提升到了17.2%,均匀化热处理使得铸态合金中部分元素的偏析能够均匀分布在基体中,从而实现了合金的强度和塑性的同步提升。     

Effect of Y Addition on Microstructure and Mechanical Properties of TiAl-based Alloys Prepared by SPS

采用双步机械球磨和放电等离子烧结(SPS)相结合的方法制备 Ti-45Al-2Cr-2Nb-1B-0.5Ta(at%)和 Ti-45Al-2Cr-2Nb-1B-0.5Ta-0.225Y(at%)2 种 TiAl 基合金(简称 TA 合金和 TAY 合金),并研究稀土元素 Y 对 TiAl 基合金显微组织和力学性能的影响。结果表明,通过双步机械球磨后的粉末形状比较规则,颗粒尺寸范围在 20~40 μm之间。经过 SPS 烧结的 TiAl 基合金块体主要由 TiAl相和 Ti3Al 相组成,还有少量的 Ti2Al 相和 TiB2相。SPS 烧结的 TA 合金块体试样等轴晶粒的尺寸在 100~400 nm 之间,合金的室温压缩强度为 2614 MPa,压缩率为 20.57%;而对于加入了稀土元素 Y 的 TAY 合金而言,等轴晶粒尺寸明显减小,合金的室温压缩强度为 2677 MPa,压缩率为 22.91%,跟 TA 合金相比力学性能有所改善。显微硬度的测试结果表明,SPS 烧结的 TA 合金的显微硬度要明显高于 TAY 合金。通过对压缩断口进行观察发现,SPS 烧结的 2 种 TiAl 基合金均为沿晶断裂。     

Microstructure and mechanical properties of the TiZrNbMoTa refractory high-entropy alloy produced by mechanical alloying and spark plasma sintering

The equiatomic refractory high entropy alloy (HEA) TiZrNbMoTa was investigated. The alloyed powders with face-centered cubic (FCC) structured solid solution phase were prepared by mechanical alloying (MA) and then sintered by spark plasma sintering (SPS) at 1300, 1400, 1500, and 1600 °C. The microstructure and mechanical properties of the bulk alloy were investigated. The body-centered cubic (BCC) structured solid solution phase and the ZrO₂ phase precipitated from the FCC structured solid solution phase during cool-down from sintering. The highest compression fracture strength (3759 MPa) and fracture strain (12.1%) were obtained in the refractory HEA sintered at 1400 °C. The grain boundary strengthening, precipitation strengthening, solid solution strengthening, transformation-induced plastic (TRIP) effect, and toughening effect of the ZrO₂ phase are the important factors for the high strength and ducitily of the refractory HEA prepared in this study.     

Microstructure and transformation of Al-containing nanostructured 316L stainless steel coatings processed using spark plasma sintering

Three austenitic stainless steel alloys containing 0, 2 and 6 wt.% Al were prepared by cryomilling and spark plasma sintering. It was shown that aluminum influences the strain-induced phase transformation that occurs during milling. The milled powders consisted of finely dispersed particles with the powder particle size distribution increasing with aluminum concentration. Consolidation of the SS0Al (stainless steel containing 0 wt.% Al) powder via the spark plasma sintering (SPS) process onto a solid stainless steel substrate yields an equiaxed structure due to the original particle morphology resulting from cryomilling. The SS2Al and SS6Al SPS consolidated powder coatings exhibit a lamellar structure due to the increased aspect ratio of the particles. The degree to which the BCC structure induced during cryomilling of all three powder systems reverted to FCC was dependent upon the Al content. The SPS process was found to minimally influence the FCC recovery compared to conventional powder consolidation heat treatments. The energy supplied by the SPS process was insufficient to overcome the activation energy governing the rearrangement of dislocations required to complete the FCC recovery. The microhardness of the coatings processing using SPS was found to be highly dependent on the Al content by controlling the ratio of the BCC/FCC crystals in the formed coating.     

Microstructures and mechanical properties of TiAl alloy prepared by spark plasma sintering

A fine-grained TiAl alloy with a composition of Ti-47%Al(mole fraction) was prepared by double mechanical milling(DMM) and spark plasma sintering(SPS). The relationship among sintering temperature, microstructure and mechanical properties of Ti-47%Al alloy was studied by X-ray diffractometry(XRD), scanning electron microscopy(SEM) and mechanical testing. The results show that the morphology of double mechanical milling powder is regular with size of 20?40 μm. The main phase TiAl and few phases Ti₃Al and Ti₂Al were observed in the SPS bulk samples. For samples sintered at 1000 °C, the equiaxed crystal grain was achieved with size of 100?250 nm. The samples exhibited compressive and bending properties at room temperature with compressive strength of 2013 MPa, compression ratio of 4.6% and bending strength of 896 MPa. For samples sintered at 1100 °C, the size of equiaxed crystal grain was obviously increased. The SPS bulk samples exhibited uniform microstructures, with equiaxed TiAl phase and lamellar Ti₃Al phase were observed. The samples exhibited compressive and bending properties at room temperature with compressive strength of 1990 MPa, compression ratio of 6.0% and bending strength of 705 MPa. The micro-hardness of the SPS bulk samples sintered at 1000 °C is obviously higher than that of the samples sintered at 1100 °C. The compression fracture mode of the SPS TiAl alloy samples is intergranular fracture and the bending fracture mode of the SPS TiAl alloy samples is intergranular rupture and cleavage fracture.     

Microstructure and Mechanical Behavior of FeNiCoCr and FeNiCoCrMn High-Entropy Alloys Fabricated by Powder Metallurgy

The present work reports a systematic investigation on phase evolution,microstructure and microstructure-property relationship of two typical face-centered cubic(FCC) structured high-entropy alloys(HEAs),FeNiCoCr and FeNiCoCrMn,prepared via mechanical alloying(MA) followed by spark plasma sintering(SPS).Following 50 h of MA,the two HEAs consisted of a mixture of FCC and body-centered cubic phases.Following SPS,the bulk FeNiCoCr alloy showed a primary FCC phase with a small amount of Cr_(23)C_6 and Cr_2 O_3 contaminants,while the bulk FeNiCoCrMn alloy was composed of a primary FCC phase with some(Cr,Mn)_(23)C_6 and MnCr_2 O_4 contaminants.The average grain size of the primary FCC phase in the bulk FeNiCoCr alloy was ～416 nm,while that of the primary FCC phase in the bulk FeNiCoCrMn alloy was ～547 nm.The yield strength,compressive strength and strain-to-failure of the bulk FeNiCoCr alloy are 1525 MPa,1987 MPa and 24.4%,respectively,whereas those of the bulk FeNiCoCrMn alloy are 1329 MPa,1761 MPa and 21.9%,respectively.It suggests that the bulk FeNiCoCrMn exhibited lower strength and plasticity in comparison with the bulk FeNiCoCr alloy.Clearly,the smaller grain size of the primary FCC phase in the FeNiCoCr alloy is mainly responsible for the better mechanical performance.     

机械合金化和烧结工艺对Al-Ni-Y-C0-La合金显微组织及力学性能的影响

通过气雾化方法制备Al86Ni7Y4．5Co1La1.5（摩尔分数,％）合金粉末。首先,将粉末进行不同时间的球磨,然后在不同的烧结温度及保压时间等条件下对粉末分别进行热压烧结和放电等离子烧结。通过X射线衍射仪（XRD）,扫描电镜（sEM）以及透射电镜（TEM）对粉末和块体材料的显微组织和形貌进行表征。结果表明：在特定球磨参数下球磨100h以上可以产生非晶,而且通过放电等离子烧结可以得到非晶／纳米晶块体材料,然而这种材料的相对密度较低。通过热压烧结可制备抗压强度为650MPa的Al86Ni7Y4．5Co1La1.5纳米块体材料。     

Alloying behavior and novel properties of CoCrFeNiMn high-entropy alloy fabricated by mechanical alloying and spark plasma sintering

An equiatomic CoCrFeNiMn high-entropy alloy was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). During MA, a solid solution with refined microstructure of 10 nm which consists of a FCC phase and a BCC phase was formed. After SPS consolidation, only one FCC phase can be detected in the HEA bulks. The as-sintered bulks exhibit high compressive strength of 1987 MPa. An interesting magnetic transition associated with the structure coarsening and phase transformation was observed during SPS process.     

双步球磨与放电等离子烧结制备细晶TiAl合金

采用双步球磨法和放电等离子烧结(SPS)技术制备细晶Ti-47Al(at%)合金,利用扫描电子显微镜(SEM)、X射线衍射(XRD)仪以及透射电子显微镜(TEM)等分析测试手段对球磨后的粉末形貌结构、相组成以及烧结块体的显微组织结构进行观察和分析。结果表明:双步球磨粉末的颗粒形状较规则,其颗粒尺寸在20~40μm之间,内部结构均匀,主要由TiAl和Ti3Al相组成。放电等离子烧结后的块体主要由主相TiAl和少量的Ti3Al相及Ti2Al相组成,随着烧结温度的升高,Ti3Al相含量有所增加。当烧结温度为1000℃时,烧结块体获得的主要是等轴晶组织,等轴晶粒尺寸大多数在100~250nm之间。当烧结温度为1100℃时,烧结块体致密、无孔洞,等轴晶粒有明显长大的现象,显微组织主要由等轴状的TiAl相和片层状的Ti3Al相组成。     

CoCrxNi中熵合金组织及力学性能研究

以等原子比CoCrNi中熵合金为基础,采用真空电弧熔炼炉制备了CoCr_xNi(x=1.0, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, at%)中熵合金,研究了Cr含量对合金微观组织及力学性能的影响。结果表明:CoCr_xNi(x=1.0, 1.5, 1.6)中熵合金为单一的面心立方相(fcc);随着Cr元素含量增加,CoCr_xNi(x=1.7, 1.8, 1.9, 2.0)中熵合金的fcc相基体中析出了体心立方相的富Cr条状组织;合金的强度、硬度随着Cr元素含量的增加而不断提高,但塑性恶化;与等原子比CoCrNi中熵合金相比,CoCr_1.7Ni中熵合金在保持较高塑性的同时,强度、硬度显著提高。     

等离子体烧结制备TiNi合金的表征

将高能球磨制备的原子比为1:1的Ti Ni合金粉进行等离子体真空烧结。利用XRD、EDS和SEM对合金粉和烧结样进行了成分与微观形貌的表征,同时对烧结样进行了硬度测试。结果表明:球磨22 h后Ti Ni粉呈非晶态粉末,球磨30 h后的TiNi合金粉发生了明显的固相反应,生成了TiNi、Ni_3Ti、Ti_3Ni_4等物相。等离子体烧结样的物相是Ti Ni,Ni_4Ti_3、Ni_3Ti和Ti_2Ni。平均晶粒尺寸约2μm,平均硬度(HV)达到9000 MPa,自然时效1年后的平均硬度达到6800MPa,是常规电弧熔炼法制备的Ti Ni合金的2~5倍。