原位生成TiB_2/Al-Si-Mg复合材料的组织与性能

结合LSM法和MCR法原位反应生成TiB2 粒子增强Al Si Mg复合材料。研究发现 :原位生成TiB2 粒子呈等轴状且尺寸 <1μm ,大都均匀分布在共晶组织中 ,与共晶Si交织在一起 ,在α(Al)中只有少量的TiB2 粒子 ;原位TiB2 粒子可明显强化Al Si Mg复合材料 ,且随着TiB2 粒子数量的增加 ,强化效果也随之提高 ,而且延伸率也略有升高 ,如 6 %TiB2 /ZL10 4复合材料室温拉伸强度可达 2 96MPa ,延伸率为 5 .5 %;热处理 (T6)可将共晶Si由原先的连续棒状变为孤立的颗粒状 ,大幅度提高材料抗拉强度 ,使 6 %TiB2 /ZL10 4复合材料室温拉伸强度达386MPa ,而材料仍属于韧性材料     

在位生成TiB2／Al—Si—Mg复合材料的组织与性能

结合LSM法和MCR法原位反应生成TiB2粒子增强Al-Si-Mg复合材料。研究发现,原位生成TiB2粒子呈等轴状且尺寸＜1um,大都均匀分布在共晶组织中,与共晶Si交织在一起,在α（Al)中只有少量的TiB2粒子。原位TiB2粒子可明显强化Al-Si-Mg复合材料,且随着TiB2粒子数量的增加,强化效果也随之提高,而且延伸率也略有升高,如6％TiB2/Zl104复合材料室温拉伸强度可达296MPa,延伸率为5．5％,热处理（T6)可将共晶Si由原先的连续棒状变为孤立的颗粒状,大幅度提高材料抗拉强度,使6％TiB2/Zl104复合材料室温拉伸强度达386MPa,而材料仍属于韧性材料。     

原位自生TiB2／7055复合材料的组织与力学性能

对原位自生亚微米TiB2/7055铝基复合材料的微观组织与力学性能进行了研究.结果表明,采用混合盐法反应工艺制备的TiB2含量为12%的7055复合材料.颗粒形状大小均匀,尺寸在200～500 mm之间,适量加入活性元素Mg,可以改善TiB2颗粒与铝基体界面润湿性,有效抑制颗粒的团聚,抗拉强度达到718 MPa,屈服强度达到679 MPa,伸长率达到4.2%,弹性模量达到86 GPa,复合材料拉伸断口呈韧性断裂特征,TiB2与基体界面的破坏以脱粘机制为主.     

混杂增强(CNTs+TiB2)/Cu复合材料制备与性能

本文以碳纳米管（CNTs）和TiB2颗粒作为增强相,首先利用球磨、表面吸附和热压烧结相结合技术制备具有层叠结构的CNTs/Cu复合材料,改善了CNTs在铜基复合材料中易团聚问题。CNTs/Cu复合材料的致密度和导电率随CNTs含量增加而降低,抗拉强度和伸长率随CNTs含量增加先升高后降低,当含量为0.1 wt.%时综合性能最优,致密度、导电率和抗拉强度分别为97.57%、91.2 %IACS和252 MPa。而球磨后热压烧结的1 wt.% TiB2/Cu复合材料致密度、导电率和抗拉强度分别为97.61%、58.3 %IACS和436 MPa。在此基础上,将TiB2颗粒原位引入到具有层叠结构的CNTs/Cu复合材料,制备获得混杂增强(CNTs+TiB2)/Cu复合材料。相比单一CNTs（或TiB2）增强铜基复合材料,(CNTs+TiB2)/Cu复合材料的强度提升显著。其中,(0.1 wt.% CNTs+1 wt.% TiB2)/Cu复合材料的导电率和抗拉强度分别为56.4 %IACS和531 MPa,相比1 wt.% TiB2/Cu,其导电率仅降低3.3%,而抗拉强度则升高21.8%。这主要归因于片层间CNTs可起承担和传递载荷作用,同时片层间弥散分布的TiB2颗粒可以钉扎位错,两种强化机制共同作用使(CNTs+TiB2)/Cu复合材料的抗拉强度显著提升。     

TiB_2含量对原位反应合成TiB_2/B_4C复合材料的组织结构和力学性能的影响(英文)

以B4C,TiO2和石墨粉为原料,采用原位反应热压烧结工艺(2050℃,35MPa,1h)制备了致密的TiB2含量为10%～40%(体积分数)的TiB2/B4C复合材料,并对复合材料的组织结构和力学性能进行了研究。扫描电子显微镜和透射电子显微镜分析结果表明:在B4C晶内及晶界处均匀分布着纳米或亚微米级的TiB2颗粒,随着TiB2含量的增加,弹性模量和断裂韧性明显增大,而弹性模量和抗弯强度却随之减小。40%(体积分数)TiB2/B4C复合材料具有高的断裂韧性,高达8.2MPam1/2,主要增韧机制由微裂纹增韧和裂纹偏转增韧。     

原位自生Al3Tip/Al复合材料的制备及其拉伸性能

采用直接反应法制备不同Al3Ti含量的Al3Tip/Al原位自生复合材料;分别在室温和高温下测试复合材料的拉伸性能,对比研究了Al3Ti含量和温度对复合材料拉伸性能的影响.结果表明:Al3Ti含量增大,则其抗拉强度和伸长率均明显降低;高温下复合材料的抗拉强度比室温时降低,伸长率反而有所增大.针对此现象,对Al3Tip/Al原位自生复合材料的拉伸断裂机理进行了讨论.     

原位TiB2颗粒增强铝基复合材料及其力学性能

对原位反应合成TiB2／A356铝基复合材料微观组织和力学拉伸性能进行了研究。结果表明，原位反应生成的颗粒增强相在复合材料基体中分布均匀，基体与颗粒间的界面洁净。复合材料强度随着颗粒含量的增加显著提高，与基体合金相比，TiB2质量分数为8％的TiB2／A356复合材料强度和弹性模量的提高幅度约为28％，TiB2质量分数为16％的TiB2／A356复合材料强度和弹性模量的提高幅度约为35％。复合材料的断裂主要是由于基体与颗粒界面脱粘，在拉伸应力作用下由此萌生微裂纹并扩展，导致界面处的基体撕裂，从而降低复合材料塑性。     

原位自生TiB_2/A356复合材料组织及性能的研究

采用原位自生的方法成功制备了TiB_2/A356复合材料,研究了不同TiB_2颗粒含量对TiB_2/A356复合材料组织及力学性能的影响。结果表明,TiB_2颗粒的尺寸为150~560nm时对复合材料有显著地细化、抑制枝晶长大的作用。随着TiB_2颗粒含量的增加,复合材料的强度随之升高而伸长率降低。复合材料的屈服强度为242~265 MPa,抗拉强度为270~297 MPa,伸长率为4.2%~5.8%。     

原位自生TiB增强Ti-55531合金复合材料组织与力学性能研究

采用真空自耗电弧熔炼及近等温热塑性变形方法制备了原位自生TiB/Ti-55531复合材料。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)及万能材料试验机等研究了增强相含量对其组织与力学性能的影响规律，并分析其失效断裂机制。结果表明，热处理态TiB/Ti-55531复合材料的组织特征为α相、TiB增强相弥散分布于β基体。随着TiB增强相的引入及含量增加，复合材料的基体晶粒明显细化，沿晶界分布的粗条状α相逐渐球化，抗拉强度、屈服强度、杨氏模量明显增加，延伸率有不同程度降低。2vol%TiB/Ti-55531复合材料的强塑性匹配较好，抗拉强度为1444.2 MPa,屈服强度为1421.4 MPa,杨氏模量为115.5 GPa,延伸率为9.2%。随着TiB增强相的引入及含量增加，拉伸试样断口的韧窝数量减少，深度变浅，断裂机制逐渐从韧性断裂向混合断裂转变。     

超声化学原位合成纳米Al2O3颗粒增强铝基复合材料的微观组织与力学行为

利用超声化学熔体原位反应技术合成了(Al2O3)np/Al复合材料,采用SEM与XRD对复合材料的微观组织和成分进行研究,并通过原位拉伸试验及断裂表面研究分析了该复合材料的断裂行为.结果表明:高能超声产生的局部高压能提供分散团聚纳米颗粒所需的最小压强(约17.2MPa),增强相颗粒数增多,分散较好,Al2O3颗粒在熔体中的形成机制为反应-溶解-析出;该复合材料的抗拉强度及伸长率分别达到116MPa和28.31％,较未施加高能超声作用的复合材料分别提高了52.63％和24.38％;该复合材料的室温拉伸断口表现为韧窝特征,为塑性断裂.     

Fe-8Mn-xAl-0.2C冷轧中锰钢的组织与性能

利用场发射扫描电镜、电子背散射衍射技术、X射线衍射仪及电子万能试验机等对Fe-8Mn-xAl-0.2C(x=0, 3)冷轧中锰钢的微观组织与性能进行了研究。结果表明,Al的添加使奥氏体化温度明显升高。经高温临界区退火后得到了等轴的奥氏体与铁素体双相组织。添加Al提高了奥氏体的稳定性,影响了试验钢变形过程中的应变硬化行为,材料塑性得到改善。Fe-8Mn-0.2C冷轧试验钢在625℃退火获得了最优综合力学性能,抗拉强度为1220 MPa,伸长率为44%,强塑积为54 GPa·%;Fe-8Mn-3Al-0.2C冷轧试验钢在710℃退火获得了最优综合力学性能,抗拉强度为970 MPa,伸长率为58%,强塑积为56 GPa·%。此外,Al的添加扩大了试验钢获得优异力学性能的退火温度范围。     

碳纤维-FeCoCrNiAl高熵合金颗粒混杂增强7075铝基复合材料的力学性能及断裂行为

为探究双相增强体对铝基复合材料拉伸性能和断裂行为的影响,采用真空热压烧结工艺在580 ℃,30 MPa条件下保温10 min制备了FeCoCrNiAl高熵合金颗粒增强7075铝基复合材料（HEA_p/Al）,Ni-Co-P镀层修饰碳纤维增强7075铝基复合材料（CF/Al）和FeCoCrNiAl高熵合金颗粒及Ni-Co-P镀层修饰碳纤维混杂增强铝基复合材料（CF-HEA_p/Al）。并对不同复合材料微观结构及拉伸性能进行分析表征及比较。结果表明：CF-HEA_p/Al复合材料的屈服强度（YS）与极限拉伸强度（UTS）随纤维含量的升高（体积分数由0至40%）呈现先增大后降低的变化,延伸率则逐渐降低。鉴于Ni-Co-P镀层修饰碳纤维与FeCoNiCrAl高熵合金颗粒的混杂强化效应, CF-HEA_p/Al复合材料的YS和UTS较HEA_p/Al与CF/Al复合材料明显提高,且其断口表现出基体韧性断裂及纤维拔出与断裂的多种失效特征。     

Effect of Hot Extrusion on Microstructures and Properties of TiB2/AZ31 Magnesium Based Composites

采用原位合成-半固态搅拌铸造法制备了TiB2/AZ31镁基复合材料,研究了热挤压对TiB2/AZ31镁基复合材料组织和力学性能的影响。结果表明：热挤压不仅能显著细化合金组织,而且能有效改善TiB2颗粒分布的均匀性。与铸态AZ31镁合金相比,铸态TiB2/AZ31镁基复合材料的硬度、抗拉强度都有一定程度的提高。经过热挤压后,TiB2/AZ31镁基复合材料的硬度和抗拉强度分别比基体合金提高了126.2%和98.8%,达到950 MPa和322 MPa。磨损表面形貌显示,TiB2颗粒的引入以及对TiB2/AZ31镁基复合材料进行热挤压,都可有效地提高材料的耐磨性。     

Tensile and Fracture Properties of 15 vol% SiC_p/2009Al Composites Fabricated by Hot Isostatic Pressing and Hot Extrusion Processes

15 vol% silicon carbide particle （SiCp）-reinforced 2009A1 matrix （15 vol% SiCp/2009A1） composites were fabricated by hot isostatic pressing （HIP） and hot extrusion processes. The tensile and fracture properties of 15 vol% SiCp/ 2009Al were studied. The results showed that hot extrusion increased the ultimate tensile strength （UTS）, yield strength （YS）, elongation （EL）, reduction in area （RA）, and fracture toughness of the composites. The heat treatment resulted in the increase in UTS, YS, and fracture toughness, but a decrease in EL and RA. Both hot extrusion and heat treatment had negligible effects on elastic modulus （E）. With the increase of SiCp size, the UTS, YS, and E decreased, but the EL and RA increased. The fracture toughness increased first and then decreased with increasing SiCp size, and when the SiCp size was about 7 μm, the composites obtained the maximum fracture toughness value of 31.74 MPa m^1/2.     

Developing high performance squeeze cast Al-Cu alloys with high Fe and Cu contents

In this paper, the microstructural evolution and mechanical properties of squeeze cast Al-Cu alloys with different amounts of Cu and Fe after T7 heat treatment were investigated using various methods, including optical microstructure (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analyzer (EPMA), and tensile testing. Results show that better comprehensive mechanical properties of squeeze cast Al-Cu alloys can be achieved by designing the Fe and Cu contents. These results can be attibuted to an increase in precipitate particles in the α(Al) matrix and the formation of nano-sized iron-rich intermetallics (IRIs). Ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) of the Al-6.5Cu-0.6Mn-1.0Fe alloy were as high as 314 MPa, 293 MPa, and 6 %, respectively. These values were close to those of Al-Si alloys with high Fe content (1.0 %) under applied pressure, and this indicates the high potential for developing recycled squeeze cast Al-Cu cast alloys.     

Effect of Ti-6Al-4V particle reinforcements on mechanical properties of Mg-9Al-1Zn alloy

Mg-9Al-1Zn (AZ91) magnesium matrix composites reinforced by Ti-6Al-4V (TC4) particles were successfully prepared via powder metallurgical method. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) showed a mountain-like tendency with the increase of the TC4 content. The mechanical properties of AZ91 magnesium matrix composites reached the optimal point with TC4 content of 10 wt.%, realizing YS, UTS, and EL of 335 MPa, 370 MPa, and 6.4%, respectively. The improvement of mechanical properties can be attributed to the effective load transfer from the magnesium matrix to the TC4 particles, dislocations associated with the difference in the coefficient of thermal expansion, good interfacial bonding between the Mg matrix and TC4 particles, and grain refinement strengthening.     

Tensile and Fracture Properties of 15 vol% SiCp/2009Al Composites Fabricated by Hot Isostatic Pressing and Hot Extrusion Processes

15 vol% silicon carbide particle (SiC_p)-reinforced 2009Al matrix (15 vol% SiC_p/2009Al) composites were fabricated by hot isostatic pressing (HIP) and hot extrusion processes. The tensile and fracture properties of 15 vol% SiC_p/2009Al were studied. The results showed that hot extrusion increased the ultimate tensile strength (UTS), yield strength (YS), elongation (EL), reduction in area (RA), and fracture toughness of the composites. The heat treatment resulted in the increase in UTS, YS, and fracture toughness, but a decrease in EL and RA. Both hot extrusion and heat treatment had negligible effects on elastic modulus (E). With the increase of SiC_p size, the UTS, YS, and E decreased, but the EL and RA increased. The fracture toughness increased first and then decreased with increasing SiC_p size, and when the SiC_p size was about 7 μm, the composites obtained the maximum fracture toughness value of 31.74 MPa m^1/2.     

Effects of under-aging treatment on microstructure and mechanical properties of squeeze-cast Al-Zn-Mg-Cu alloy

The effects of under-aging treatment on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloy produced by squeeze casting were investigated using optical microscopy (OM), X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and hardness and tensile testing. The results showed that most of secondary phases were dissolved into α(Al) matrix while no significant grain growth happened under the condition of solution treatment at 470 °C for 4 h. Due to the strengthening effect of GP zones, for alloys treated by under-aging process, the increase of aging time and aging temperature improved the ultimate tensile strength (UTS) and yield strength (YS), but decreased the elongation (δ) to some extent. By utilizing appropriate aging time and temperature, the best combination of strength and ductility could be obtained to fulfill the design requirements of automobile components.     

Microstructure and mechanical properties of high strength Mg−15Gd−1Zn−0.4Zr alloy additive-manufactured by selective laser melting process

In order to verify the feasibility of producing Mg−rare earth (RE) alloy by selective laser melting (SLM) process, the microstructure and mechanical properties of Mg−15Gd−1Zn−0.4Zr (wt.%) (GZ151K) alloy were investigated. The results show that fine grains (~2 μm), fine secondary phases and weak texture, were observed in the as-fabricated (SLMed) GZ151K Mg alloy. At room temperature, the SLMed GZ151K alloy has a yield strength (YS) of 345 MPa, ultimate tensile strength (UTS) of 368 MPa and elongation of 3.0%. After subsequent aging (200 °C, 64 h, T5 treatment), the YS, UTS and elongation of the SLMed-T5 alloy are 410 MPa, 428 MPa and 3.4%, respectively, which are higher than those of the conventional cast-T6 alloy, especially with the YS increased by 122 MPa. The main strengthening mechanisms of the SLMed GZ151K alloy are fine grains, fine secondary phases and residual stress, while after T5 treatment, the YS of the alloy is further enhanced by precipitates.