Al_3Zr和Al_3Nb作为铝合金晶粒细化剂的晶体学研究(英文)

利用edge-to-edge matching模型从晶体学角度研究Al3Zr和Al3Nb两种金属间化合物作为铝合金晶粒细化剂的有效性。结果表明,Al3Zr和Al3Nb两种金属间化合物和铝之间的原子间距错配和面间距错配值都很小。此外,模型预测Al3Zr和Al3Nb两种金属间化合物与铝之间存在良好的晶粒取向关系。根据模型理论可以从晶体学角度证明这两种金属间化合物对铝合金是有效的晶粒异质形核细化剂。本晶体学研究为包晶铝合金Al-Zr和Al-Nb中出现的明显晶粒细化现象提供了合理解释,同时为理解晶粒细化机理提供了新方法。

Effect of Inoculation on Phase Formation and Indentation Hardness Behaviour of Zr<SUB>47.5</SUB>Cu<SUB>45.5</SUB>Al<SUB>5</SUB>Co<SUB>2</SUB>and Zr<SUB>65</SUB>Cu<SUB>15</SUB>Al<SUB>10</SUB>Ni<SUB>10</SUB>Bulk Metallic Glass Matrix Composites

Bulk metallic glass matrix composites have emerged as a new potential material for structural engineering applications owing to their superior strength, hardness and high elastic strain limit. However, their behaviour is dubious. They manifest brittleness and inferior ductility which limit their applications. Various methods have been proposed to overcome this problem. Out of these, introduction of foreign particles (inoculants) during solidification has been proposed as the most effective. In this study, an effort has been made to delimit this drawback. A systematic tale has been presented which explains the evolution of microstructure in Zr47.5Cu45.5Al5Co2 and Zr65Cu15Al10Ni10 bulk metallic glass matrix composites with varying percentage of ZrC inoculant as analysed by secondary electron, back scatter electron imaging of “as cast” unetched samples and indentation microhardness testing. Secondary electron imaging of indents was also performed which shows development of shear transformation zones at edges of square of indents. Mostly, no cracking was observed, few cracks bearing Palmqvist morphology were witnessed in samples containing lower percentage of inoculant. A support is provided to hypothesis that inoculations remain successful in promoting phase formation and crystallinity and improving toughness.

Effect of Single Pass Laser Surface Treatment on Microstructure Evolution of Inoculated Zr<SUB>47.5</SUB>Cu<SUB>45.5</SUB>Al<SUB>5</SUB>Co<SUB>2</SUB>and Non-Inoculated Zr<SUB>65</SUB>Cu<SUB>15</SUB>Al<SUB>10</SUB>Ni<SUB>10</SUB>Bulk Metallic Glass Matrix Composites

Bulk metallic glass matrix composites are advocated to be material of future owing to their superior strength, hardness and elastic strain limit. However, they possess poor toughness which makes them unusable in any structural engineering application. Inoculation has been used as effective mean to overcome this problem. Zr47.5Cu45.5Al5Co2 bulk metallic glass matrix composites (BMGMC) inoculated with ZrC have shown considerable refinement in microstructure owing to heterogeneous nucleation. Efforts have also been made to exploit modern laser-based metal additive manufacturing to fabricate BMGMC parts in one step. However, the effect of laser on inoculated material is unknown. In this study, an effort has been made to apply single pass laser surface treatment on untreated and inoculated BMGMC samples. It is observed that laser treatment not only refine the microstructure but result in change of size, morphology and dispersion of CuZr B2 phase in base metal, heat affected zone and fusion zone in Zr47.5Cu45.5Al5Co2. A similar effect is observed for β-Zr and Zr2Cu in non-inoculated Zr65Cu15Al10Ni10. This effect is documented with back scatter electron imaging.

Laser directed energy deposited, ultrafine-grained functional titanium-copper alloys tailored for marine environments: Antibacterial and anti-microbial corrosion studies

The microorganism-rich nature of the ocean imposes great challenges to the structural integrity of met-als over their service lifespan,including titanium(Ti)alloys,which are usually prone to microbiologically influenced corrosion(MIC).So,multifunctional anti-MIC Ti alloys need to be developed and studied.This paper investigates the effect of copper(Cu)concentration on the MIC resistance of a series of additively manufactured,ultrafine-grained Ti-x Cu(x=3.5,6.5 and 8.5 in wt.%)alloys.The dependence of the cor-rosion resistance and MIC resistance on the Cu concentration of Ti-Cu alloy is interpreted considering all conceivable mechanisms.The mechanisms for excellent corrosion resistance of Ti-Cu alloy in seawater are attributed to the strong passive film and small surface potential difference between phases.Microstruc-tural characterization reveals that uniformly distributed,nanosized Ti_(2) Cu phase led to increased reactive oxygen species in the bacterial membrane,which is the root reason for the superb anti-bacterial property(99.2%)for Ti-8.5Cu.Compared to pure Ti and Ti-6Al-4V,Ti-8.5Cu alloy features both high strength(yield stress>1000 MPa)and the best MIC resistance(97.5%).The combination of such balanced properties enables this functional 3D printed Ti-Cu alloy to become an ideal material for load-bearing applications in the marine environment.

Recent advances in biodegradation controls over Mg alloys for bone fracture management: A review

Magnesium(Mg) alloys possess comparable physical and mechanical properties to bone, making them an outstanding candidate of implant materials for bone fracture treatment. In addition to the excellent biocompatibility, and bioactivity, the engagement of Mg alloys is key for a number of biological functionalities in the human body. The unique biodegradation nature of Mg alloy implants implies that it may not require a secondary removal procedure when the expected supporting tasks accomplish, as they may simply and safely "disappear" over time. Nonetheless, the demonstrated drawback of potentially rapid degradation, is an issue that must be addressed appropriately for Mg implants and is consequently given unique attention in this review article. Herein, the critical criteria and the state-of-the-art strategies for controlling the degradation process of Mg alloys are reported. Furthermore, future developments of biodegradable Mg and its alloys systems with satisfactory specifications for clinical trials and deployment,are discussed. This review aims to provide information to materials scientists and clinical practitioners in the context of developing practical biodegradable Mg alloys.