Corrosion fatigue of a magnesium alloy in modified simulated body fluid

Magnesium with its mechanical properties and nontoxicity is predetermined as a material for biomedical applications; however, its high reactivity is a limiting factor for its usage. Powder metallurgy is one of the promising methods for the enhancement of material mechanical properties and, due to the introduced plastic deformation, can also have a positive influence on corrosion resistance. Pure magnesium samples were prepared via powder metallurgy. Compacting pressures from 100 MPa to 500 MPa were used for samples' preparation at room temperature and elevated temperatures. The microstructure of the obtained compacts was analyzed in terms of microscopy. The three-point bending test and microhardness testing were adopted to define the compacts' mechanical properties, discussing the results with respect to fractographic analysis. Electrochemical corrosion properties analyzed with electrochemical impedance spectroscopy carried out in HBSS (Hank's Balanced Salt Solution) and enriched HBSS were correlated with the metallographic analysis of the corrosion process. Cold compacted materials were very brittle with low strength (up to 50 MPa) and microhardness (up to 50 HV (load: 0.025 kg)) and degraded rapidly in both solutions. Hot pressed materials yielded much higher strength (up to 250 MPa) and microhardness (up to 65 HV (load: 0.025 kg)), and the electrochemical characteristics were significantly better when compared to the cold compacted samples. Temperatures of 300 • C and 400 • C and high compacting pressures from 300 MPa to 500 MPa had a positive influence on material bonding, mechanical and electrochemical properties. A compacting temperature of 500 • C had a detrimental effect on material compaction when using pressure above 200 MPa.

Section: Introductionmentioning

confidence: 99%

Characterization of Powder Metallurgy Processed Pure Magnesium Materials for Biomedical Applications

Zapletal

Březina

Krystýnová

et al. 2017

“…For different Mg alloys, RRFS may range from 30 to 70%, showing the significant impact of the corrosive medium on the fatigue resistance of Mg and its alloys [86,91]. Failure due to dynamic loading in a corrosive environment is related to corrosion fatigue (CF) and relations can be drawn from SCC.…”

Section: Corrosion Fatigue (Cf)mentioning

confidence: 99%

“…However, Fairman and Bray [98] argued against Pugh et al's model as they either do not detect oxide layers on the fracture surfaces or do not observe brittle fracture on Mg-Al alloys in chloride solutions. Several authors [77,78,83,86,101,102] agreed that cleavage fracture is a consequence of hydrogen induced Mg matrix embrittlement. Presence of hydrogen is a consequence of the Mg corrosion mechanism in aqueous solutions (see Section 2); according to the cathodic partial reaction, one molecule of hydrogen gas is produced for each atom of Mg dissolved in the human body, but hydrogen is also produced at an anodic potential due to the negative difference effect (NDE, detailed in Section 4).…”

mentioning

confidence: 99%

Mg and Its Alloys for Biomedical Applications: Exploring Corrosion and Its Interplay with Mechanical Failure

Peron

Torgersen

Berto

2017

109

Abstract:The future of biomaterial design will rely on temporary implant materials that degrade while tissues grow, releasing no toxic species during degradation and no residue after full regeneration of the targeted anatomic site. In this aspect, Mg and its alloys are receiving increasing attention because they allow both mechanical strength and biodegradability. Yet their use as biomedical implants is limited due to their poor corrosion resistance and the consequential mechanical integrity problems leading to corrosion assisted cracking. This review provides the reader with an overview of current biomaterials, their stringent mechanical and chemical requirements and the potential of Mg alloys to fulfil them. We provide insight into corrosion mechanisms of Mg and its alloys, the fundamentals and established models behind stress corrosion cracking and corrosion fatigue. We explain Mgs unique negative differential effect and approaches to describe it. Finally, we go into depth on corrosion improvements, reviewing literature on high purity Mg, on the effect of alloying elements and their tolerance levels, as well as research on surface treatments that allow to tune degradation kinetics. Bridging fundamentals aspects with current research activities in the field, this review intends to give a substantial overview for all interested readers; potential and current researchers and practitioners of the future not yet familiar with this promising material.

“…Liu et al [33] studied the HCF behavior of TC4 in simulated body fluid (SBF), the endurance limit at 1 × 10 8 cycles of TC4 decreases by 7%. The fatigue properties of magnesium alloy [34,35], ZrCuFeAlAg bulk metallic glass [36], niobium alloy [37], stainless steel [38], TiN-and DLC-coated stainless steel [39] in simulated body fluid have been studied in the recent five years. Bai et al [40], Huang et al [41], and Li et al [42,43] reported that nanocrystal surface layers by SSN are conducive to the corrosion resistance, because of the high density grain boundaries and the deeper passive film.…”

Section: Introductionmentioning

confidence: 99%

Effect of Ultrasonic Surface Impact on the Fatigue Behavior of Ti-6Al-4V Subject to Simulated Body Fluid

Cao

Wang

et al. 2017

Abstract:The effect of ultrasonic nanocrystal surface modification (UNSM) on the fatigue behavior of Ti6Al4V (TC4) in simulated body fluid (SBF) was investigated. UNSM with the condition of a static load of 25 N, vibration amplitude of 30 µm and 36,000 strikes per unit produced about 35 µm surface severe plastic deformation (SPD) layers on the TC4 specimens. One group was treated with a hybrid surface treatment (UNSM + TiN film). UNSM technique improves the micro hardness and the compressive residual stress. The surface roughness is increased slightly, but it can be remarkably improved by the TiN film. The fatigue strength of TC4 is improved by about 7.9% after UNSM. Though the current density of corrosion is increased and the pitting corrosion is accelerated, UNSM still improved the fatigue strength of TC4 after pre-soaking in SBF by 10.8%. Interior cracks initiate at the deformed carbide and oxide inclusions due to the ultrasonic impacts of UNSM. Corrosion products are always observed at the edge of fracture surface to both interior cracks and surface cracks. Coating a TiN film on the UNSMed surface helps to improve the whole properties of TC4 further.