Mechanical properties and microstructures of new Ti–Fe–Ta and Ti–Fe–Ta–Zr system alloys

β-type titanium alloys consisting of non-toxic elements, Ti–8Fe–8Ta, Ti–8Fe–8Ta–4Zr, and Ti–10Fe–10Ta–4Zr, were newly designed and developed for biomedical applications. Changes in the mechanical properties of the designed alloys with various heat treatments were discussed on the basis of the resultant microstructures. In addition, the corrosion resistance of the designed alloys was evaluated by polarization testing in Hank's solution. Conventional biomedical titanium (cp-Ti) and the titanium alloy Ti–6Al–4V ELI were also polarized for comparison.The structural phase of the designed alloys, after cold rolling and solution treatment, was only the β phase. Ultimate tensile strength and elongation to fracture of Ti–8Fe–8Ta, Ti–8Fe–8Ta–4Zr, and Ti–10Fe–10Ta–4Zr after solution treatment were 1066 MPa and 10%, 1051 MPa and 10%, and 1092 MPa and 6%, respectively. Ti–8Fe–8Ta and Ti–8Fe–8Ta–4Zr have higher strength than those of conventional biomedical titanium alloys such as Ti–6Al–4V ELI, Ti–6Al–7Nb, and Ti–13Nb–13Zr. In particular, the elongations at failure of Ti–8Fe–8Ta and Ti–8Fe–8Ta–4Zr were equal to those of Ti–6Al–4V ELI and Ti–6Al–7Nb. The designed alloys and conventional biomedical titanium alloys were spontaneously passivated in Hank's solution. The current density of cp-Ti and Ti–6Al–4V ELI was increased at a potential above 2.5 V. On the other hand, the current density of the designed alloys abruptly increased at a potential above 3.5 V. The designed alloys have the advantage over cp-Ti and Ti–6Al–4V ELI in their high resistance to pitting corrosion in biological environments.Therefore, new β-type titanium alloys designed in this study, Ti–8Fe–8Ta and Ti–8Fe–8Ta–4Zr, are expected to have good properties as biomaterials.     

致密TiC-Al2O3-Fe 金属陶瓷的自蔓延高温合成

通过自蔓延高温合成结合准热等静压法(SHS/PH IP) 制备出了致密的TiC₂Al₂O₃-20Fe 金属陶瓷。研究了延迟时间、高压持续时间、压力等工艺参数对金属陶瓷密实度的影响, 分析了金属陶瓷的相组成、微观组织及性能。结果表明, 燃烧合成过程中气体的排放和液相的存在是合成密实材料的关键, 通过优化工艺合成了密实度为97. 7% 的TiC₂Al₂O₃-20Fe 金属陶瓷。金属陶瓷由TiC、Al₂O₃ 和Fe 粘结相组成。粘结相Fe 与Al₂O₃ 之间界面光滑,Fe 与T iC 之间有一较薄扩散层。TiC₂Al₂O₃-20Fe 金属陶瓷的抗弯强度和抗压强度分别为890M Pa 和18. 4 GPa。      

Optimization of Strength‐Electrical Conductivity Properties in Al–2Fe Alloy by Severe Plastic Deformation and Heat Treatment

High‐pressure torsion at room temperature followed by two processing routes, either 1) annealing at 200 °C for 8 h or 2) elevated temperature (200 °C) high‐pressure torsion, are employed to obtain simultaneous increase in mechanical strength and electrical conductivity of Al–2 wt%Fe. The comparative study of microstructure, particle distribution, mechanical properties, and electrical conductivity for both processing routes gives the optimal combination of high mechanical strength and high electrical conductivity in Al–2Fe alloy. It is shown that while the mechanical strength is approximately the same for both processing routes (>320 MPa), high‐pressure torsion at elevated temperature results in higher conductivity (≥52% IACS) due to reduction of Fe solute atom concentration in Al matrix compared to annealing treatment. High‐pressure torsion at 200 °C has been demonstrated as a new and effective way for obtaining combination of high mechanical strength and electrical conductivity in Al–Fe alloys.

     

Microstructure and elevated temperature mechanical properties of Al–8Fe–4RE alloy fabricated by spray forming

Al–8Fe–4Ce alloy is currently manufactured by consolidating the atomized powders. With the aim to reduce the cost, spray forming process was applied in manufacturing with misch metal as raw materials. Spray forming (SF) as well as casting were employed to prepare Al–8Fe–4RE alloy, followed by hot‐press to compact the samples. The mechanical properties of SFed and cast Al–8Fe–4RE alloys are characterized at a temperature of 350 °C. The results show that the Al₃Fe phases contained in SF alloy is comparatively refined, forming needle‐shaped phases embedded in the Al matrix, and the SF alloy also showed lower degree of preferred orientation in (111) plane. Although both factors might explain the superior performance of the SF sample, the fracture appearance after tensile test at 350 °C shows that the contribution from crystallographic feature might be predominant. Spray forming is proved to be a very promising technique for manufacture of Al–Fe–Ce alloys of high strength at an elevated temperature.     

The effects of cell spacing and distribution of intermetallic fibers on the mechanical properties of hypoeutectic Al–Fe alloys

The aim of the present investigation was to contribute to provide a basis for understanding how to control solidification parameters, microstructure and mechanical strength of Al–Fe alloys. Upward directional solidification experiments have been carried-out with commercially pure Al and Al–0.5 wt.% Fe, Al–1.0 wt.% Fe and Al–1.5 wt.% Fe alloys. The tensile tests results have been correlated to cell spacing (λ₁), since cellular growth has prevailed along all obtained Al–Fe castings. The used casting assembly was designed in such way that the heat was extracted only through the water-cooled system at the bottom of the casting. In order to investigate the nature of Al–Fe intermetallic fibers, they were extracted from the aluminum-rich matrix by using a dissolution technique. These fibers were then investigated by SEM-EDAX microscopy. It was found that the ultimate tensile strength, yield tensile strength and elongation increase with decreasing cell spacing. The highest ultimate tensile strength was that obtained for the most refined microstructure, i.e. for the Al–1.5 wt.% Fe alloy sample, where a higher density of eutectic fibers was found distributed in a more homogeneous way along the casting section due to lower cell spacings. In contrast, the elongation was found to decrease with increasing solute content.     

Nanostructured β-phase Ti–31.0Fe–9.0Sn and sub-μm structured Ti–39.3Nb–13.3Zr–10.7Ta alloys for biomedical applications: Microstructure benefits on the mechanical and corrosion performances

Nanostructured Ti–31.0Fe–9.0Sn and sub-micrometer structured Ti–39.3Nb–13.3Zr–10.7Ta (wt.%) β-type alloys, exhibiting different microstructures and dissimilar mechanical properties, have been prepared by copper mold casting. The microstructure, mechanical behavior and corrosion resistance, in simulated body fluid, of both alloys have been investigated and compared to those of commercial Ti–6Al–4V. Nanoindentation experiments reveal that the Ti–31.0Fe–9.0Sn rods exhibit very large hardness (H ≈ 9 GPa) and high Young's modulus. Conversely, the Ti–39.3Nb–13.3Zr–10.7Ta alloy is mechanically softer but it is interesting for biomedical application because of its rather low Young's modulus (E ≈ 71 GPa). Concerning the corrosion performance, Ti–35Nb–7Zr–5Ta shows a corrosion behavior comparable to Ti–Al6–V4, with no potential breakdown up to 0.4 V vs. Ag|AgCl. On the contrary, the Ti–31.0Fe–9.0Sn alloy exhibits a more anodic corrosion potential, but the value is still less negative than for pure elemental Fe and Ti. From all these properties and because of the absence of toxic elements in the compositions, the Ti–39.3Nb–13.3Zr–10.7Ta and Ti–31.0Fe–9.0Sn alloys are attractive for use as metallic biomaterials.     

Second generation (low modulus) titanium alloys in total hip arthroplasty

Titanium alloys ‐ type (α+β) ‐ like Ti6Al7Nb or Ti6Al4V are widely used in cementless total hip arthroplasty due to their lower modulus, biocompatibility and enhanced corrosion resistance in comparison to Stainless Steel or Cobalt‐Chromium implant materials. Several articles report about atrophy of the proximal femur in cases where long stems with a big diameter made of (α+β) Titanium alloys with a relatively high value of the Youngs’ Modulus (110 GPa) in comparison to the Youngs’ Modulus of cortical bone (15–25 GPa) have been implanted using a prosthesis design with distal anchorage technique. Meanwhile several implant manufacturers have developed a new group of biocompatible Beta‐Titanium alloys with a lower Youngs’ Modulus around 70 GPa. This article gives an overview of the current status of available low modulus Titanium alloys including their mechanical characteristics and future developments.     

Achievement of Ultralow Elastic Modulus through Optimization of Phase Stability and Recrystallization Texture in Ti–Nb–Fe–Sn Alloys

Ti–Nb–Fe–Sn alloys with relatively low Nb content, located near the phase boundary of (β + ω)/β, are designed on the basis of electron-to-atom (e/a) ratio, d-electron alloy design concept, and Mo equivalent (Mo_eq) aiming at low Young's modulus comparable to human bone. The effect of Sn content and Nb content on the microstructure and the mechanical properties is investigated in Ti–5Nb–3Fe–(0–6)Sn (at%) and Ti–(3–9)Nb–3Fe–4Sn (at%) alloys. The composition dependence of Young's modulus and tensile strength of Ti–Nb–Fe–Sn alloys is analyzed in terms of the phase stability, ω phase, and recrystallization texture. Both Nb and Sn are effective in suppressing the athermal ω phase and stabilizing the β phase. The recrystallization texture is strongly influenced by the content of Sn and Nb. A strong {110}_β<001>_β Goss texture is formed in the Ti–5Nb–3Fe–(2–4)Sn and Ti–(3–5)Nb–3Fe–4Sn alloys. The Ti–5Nb–3Fe–4Sn alloy exhibits an exceptionally low Young's modulus of 30 GPa due to the combined effects of low stability of the β phase, a small amount of ω phase, and a strong Goss texture.     

Effect of Al and C on structure and mechanical properties of Fe–Al–C alloys

Abstract

Effect of aluminium and carbon content on the microstructure and mechanical properties of Fe–Al–C alloys has been investigated. Alloys were prepared by combination of air induction melting with flux cover (AIMFC) and electroslag remelting (ESR). The ESR ingots were hot forged and hot rolled at 1373 K. As rolled alloys were examined using optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to understand the microstructure of these alloys. The ternary Fe–Al–C alloys containing 10·5 and 13 wt-%Al showed the presence of three phases: FeAl with disordered bcc structure, Fe₃Al with ordered DO₃ structure and Fe₃AlC_0·5 precipitates with L′1₂ structure. Addition of high concentration of carbon to these alloys resulted in excellent hot workability and superior tensile at room temperature as well as tensile and creep properties at 873 K. An increase in Al content from 9 to 13 wt-% in Fe–Al–C alloys containing the same levels of carbon has no significant influence on strength and creep properties at 873 K, however resulted in significant improvement in room temperature strength accompanied by a reduction in room temperature ductility.     

Formation of a quasicrystalline phase in Al–Mn base alloys cast at intermediate cooling rates

Al-rich 94Al–6Mn and 94Al–4Mn–2Fe alloys were suction-cast to evaluate the feasibility of obtaining bulk quasicrystal-strengthened Al-alloys at intermediate cooling rates alloyed with non-toxic, easily accessible and affordable additions. The influence of different cooling rates on the potential formation of a quasicrystalline phase was examined by means of scanning and transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. Increased cooling rates in the thinnest castings entailed a change in sample phase composition. The highest cooling rates turned out to be insufficient to form an icosahedral quasicrystalline phase (I-phase) in the binary alloy. Instead, an orthorhombic approximant phase occurred (L-phase). The addition of Fe to the 94Al–6Mn binary alloy enhanced the formation of a quasicrystalline phase. At intermediate cooling rates of 10²–10³ K/s, various metastable phases were formed, including decagonal and icosahedral quasicrystals and their approximants. Rods (1 mm in diameter) composed of I-phase particles embedded in Al matrix exhibited a hardness of 1.5 GPa, much higher than the 1.1 GPa of 94Al–6Mn.     

冷轧对Al_(10)Cu_(25)Co_(20)Fe_(20)Ni_(25)高熵合金组织结构及力学性能的影响

对铸态Al10Cu25Co20Fe20Ni25高熵合金进行冷轧处理后进行室温拉伸测试,并利用X射线衍射仪(XRD)和扫描电镜(SEM)分别对其相结构、微观组织形貌及拉伸断口进行分析。结果表明:经冷轧工艺处理后,Al10Cu25Co20Fe20Ni25高熵合金硬度最大为285HV,较轧制前提高了51.6%;在变形量为40%时,抗拉强度达到最大值,为638MPa,是铸态合金的2.7倍。拉伸断口分析表明,铸态合金的断裂模式为树枝晶沿晶断裂和韧窝型延性断裂,而冷轧态合金主要为韧窝型延性断裂模式。     

High strength and ductile low density austenitic FeMnAlC steels: Simplex and alloys strengthened by nanoscale ordered carbides

Abstract

We introduce the alloy design concepts of high performance austenitic FeMnAlC steels, namely, Simplex and alloys strengthened by nanoscale ordered κ-carbides. Simplex steels are characterised by an outstanding strain hardening capacity at room temperature. This is attributed to the multiple stage strain hardening behaviour associated to dislocation substructure refinement and subsequent activation of deformation twinning, which leads to a steadily increase of the strain hardening. Al additions higher that 5 wt-% promote the precipitation of nanoscale L′1₂ ordered precipitates (so called κ-carbides) resulting in high strength (yield stress ～1·0 GPa) and ductile (elongation to fracture ～30%) steels. Novel insights into dislocation–particle interactions in a Fe–30·5Mn–8·0Al–1·2C (wt-%) steel strengthened by nanoscale κ-carbides are discussed.     

Precipitation of iron-rich intermetallics and mechanical properties of Al–Si–Mg–Fe alloys with Al–5Ti–B

Effects of added Al–5Ti–B master alloys on precipitation of iron-rich intermetallics and mechanical properties of A356 cast alloys with high Fe content (1.5?wt-%) were investigated using image analysis, scanning electron microscopy, and tensile testing. Results show that added Al–5Ti–B has apparent refinement on α (Al) grain size of A356 alloys that have high Fe content. 12?wt-% Al–5Ti–B is beneficial for improving mechanical properties of A356 cast alloys with high Fe content. Improved mechanical properties can be attributed to refined microstructure, the proper amounts of TiB₂ and Ti(AlSi)₃, and decreased porosity. An excessive amount of Al–5Ti–B deteriorates mechanical properties of alloys because it leads to the formation of large secondary intermetallics and increased porosity.     

高强度低密度大模量菲晶态Ai—Li合金

利用单辊快速凝固装置制备出高强度、低密度、大楼量的非晶态Ａｌ６１Ｌｉ２．５Ｙ２５Ｎｉ１１．５（ｗｔ－％）合金，其最大拉伸断裂强度、显微硬度和弹性模量分别为１０３９ＭＰａ、４８８ＤＰＮ和９８．７ＧＰａ．与同成分的晶态合金相比，具有较高的电极电位、较宽的电压钝化区，其腐蚀抗力为晶态合金的７倍．在恒加热速率的晶化过程中出现４个晶化峰，晶化激活能的计算表明，Ａｌ６１Ｌｉ２．５Ｙ２５Ｎｉ１１．５非晶合金的晶化过程为一级反应．     

TiC-Al2O3-Fe金属陶瓷的自蔓延高温合成研究

通过自蔓延高温合成结合准热等静压法（ＳＨＳ／ＰＨＩＰ）制备出了致密度为９７．７％的ＴｉＣ－Ａｌ２Ｏ３－２０Ｆｅ金属陶瓷（ＴＡＦ２０）。分析了金属陶瓷的相组成、微观组织及性能。结果表明：金属陶瓷由ＴｉＣ,Ａｌ２Ｏ３陶瓷颗粒和Ｆｅ粘结相组成;粘结相中Ｆｅ与Ａｌ２Ｏ３之间的界面光滑,与ＴｉＣ之间有一薄的扩散层;ＴＡＦ２０金属陶瓷的抗弯强度和抗压强度分别为８９０ＭＰａ和１８．４ＧＰａ。     

Simultaneously Improved Bendability and Strength of Al–Mg–Si–Cu–Zn Alloys by Controlling the Formation and Evolution of Primary Fe-Rich Phase

In present work, the formation, evolution, and distribution of the primary Fe-rich phase in an Al–Mg–Si–Cu–Zn–Fe–Mn alloy are coupling controlled by ultrasonic melt treatment (USMT) and thermomechanical processing (TMP). It is shown in the results that the size of grains and Fe-rich phase in the as-cast state can be greatly reduced by the applied optimum USMT at 680 °C. Additionally, the transformation rate of β-Fe-rich phase to α-Fe-rich phase can be also enhanced. After the coupling control of USMT and TMP, the number density and distribution uniformity of multiscale Fe-rich particles can be greatly increased or improved, which contributes to the fine-grained recrystallization microstructure and weakened texture. Finally, compared with the 6xxx series Al alloys (such as AA6016 and AA6111), the alloy sheet in the pre-aging state exhibits substantially improved bendability and strength (the plastic strain ratio and tensile strength are 0.67 and 304 MPa, respectively). The effect of USMT on the formation and transformation of primary Fe-rich phase and the mechanisms of improved bendability and strength are deeply discussed.     

Evaluation of cast Ti–Fe–O–N alloys for dental applications

Good mechanical properties, biocompatibility and corrosion resistance make titanium an excellent material for biomedical applications. However, when better mechanical properties than those offered by commercially pure titanium (CPTi) are needed, Ti–6Al–4V is sometimes a good alternative. Some new titanium alloys, developed as industrial structural materials, aim at an intermediate range of strength between that of CP Ti and Ti–6Al–4V. Two of these alloys are Super-TIX800™ (Ti–1% Fe–0.35% O–0.01% N) and Super-TIX800N™ (Ti–1% Fe–0.3% O–0.04% N) (both produced by Nippon Steel Corp., Japan). Besides being stronger than CP Ti, the cost of manufacturing these alloys is reportedly lower than for Ti–6Al–4V since they do not contain any expensive elements. In addition, they are not composed of elements such as aluminum or vanadium, which have caused biocompatibility concerns in medical and dental appliances. To evaluate these alloys as candidates for dental use, it is helpful to compare them to CP Ti (ASTM Grade 2) and Ti–6Al–4V (ASTM Grade 5), which have already been employed in dentistry. We evaluated the tensile properties, mold filling capacity, corrosion characteristics and grindability of these industrial alloys prepared by investment casting. Compared to the strengths of cast CPTi, the yield strength and tensile strength of these cast alloys were more than 20% and approximately 30% higher, respectively. On the other hand, both of these properties were 30% lower than for Ti–6Al–4V. Better grindability and wear resistance were additional benefits of these new alloys for dental applications.     

Microstructure and mechanical properties of asextruded Mg–xAl–5Sn–0·3Mn alloys (x = 1, 3, 6 and 9)

Properties of Mg–xAl–5Sn–0·3Mn alloys (x?=?1, 3, 6 and 9) prepared by hot extrusion are reported. The orientation relationship between Mg₂Sn precipitate and Mg matrix in Mg–9Al–5Sn–0·3Mn alloy was determined. The yield strength of the as extruded alloys initially decreased with increasing Al content, then increased for Al contents >6 wt-%. These changes are interpreted in terms of the effect of texture, grain size and second phase on the yield strength of the alloys.     

机械合金化与放电等离子烧结制备Fe-Fe3Al材料

为开发新型金属材料,采用机械合金化与放电等离子烧结的方法制备Fe-Fe3Al合金.根据Fe-Al二元相图与研究经验,对成分及工艺进行优化设计.用X射线衍射仪(XRD)对成分进行了定性分析,用扫描电子显微镜(SEM)观察了样品的表面与断口形貌,进行了能谱分析,并测试了致密度、显微硬度(HV)及抗弯强度、抗拉强度等力学性能.结果表明:对粉末进行预球磨,并在球磨前后对粉末进行搅拌混合处理,能更好地促使Fe与Al在高能球磨的过程中反应;经放电等离子烧结能够制备出Fe3Al/Fe两相材料,相对密度为99%以上,硬度为HV561,抗弯强度1426 MPa,抗拉强度640 MPa,力学性能优于文献报道的值.     

Superior mechanical properties of a selective-laser-melted AlZnMgCuScZr alloy enabled by a tunable hierarchical microstructure and dual-nanoprecipitation

Achieving high mechanical strength and ductility in age-hardenable Al7000 series (Al–Zn–Mg) alloys fabricated by selective laser melting (SLM) remains challenging. Here, we show that crack-free AlZnMgCuScZr alloys with an unprecedented strength–ductility synergy can be fabricated via SLM and heat treatment. The as-built samples had an architectured microstructure consisting of a multimodal grain structure and a hierarchical phase morphology. It consisted of primary Al₃(Sc_x,Zr_1−x) particles which act as inoculants for ultrafine grains, preventing crack formation. The metastable Mg-, Zn-, and Cu-rich icosahedral quasicrystals (I-phase) ubiquitously dispersed inside the grains and aligned as a filigree skeleton along the grain boundaries. The heat treated SLM-produced AlZnMgCuScZr alloy exhibited tunable mechanical behaviors through trade-off among the hierarchical features, including the dual-nanoprecipitation, viz, η′ phase, and secondary (Al,Zn)₃(Sc₉Zr), and grain coarsening. Less coarsening of grains and (Al,Zn)₃(Sc₉Zr) particles, due to a reduced solution treatment temperature and time, could overwhelm the more complete dissolution of I-phase (triggering more η′ phase), resulting in higher yield strength. Optimal combination of the hierarchical features yields the highest yield strength (∼647 MPa) among all reported SLM-produced Al alloys to date with appreciable ductility (∼11.6%). The successful fabrication of high-strength Al7000 series alloys with an adjustable hierarchical microstructure paves the way for designing and fine-tuning SLM-produced aluminum engineering components exposed to high mechanical loads.