PCL/HA静电纺丝纤维涂层对可降解Mg/HA复合材料的表面改性:力学性能、腐蚀和生物相容性

采用搅拌铸造和挤压法制备Mg/HA复合材料,并在其表面采用静电纺丝法涂覆聚己内酯/羟基磷灰石(PCL/HA)纤维(2.5%和5%HA,质量分数),以提高其耐腐蚀性。力学性能测试结果表明,复合材料的压缩屈服强度从73MPa(纯镁)提高到151MPa,提高了107%。SEM、EDS和XRD分析表明,HA颗粒分布在多孔涂层中。极化曲线结果表明,涂层试样的耐腐蚀性能均优于未涂覆试样。PCL涂层使样品的腐蚀电流密度降低了两个数量级。通过极化和体外腐蚀试验证明了HA在涂层中的有效性。涂层和随后形成的Ca-P层阻碍了模拟体液与基体的接触和渗透,从而起到保护表面的作用。PCL/2.5%HA涂层样品的腐蚀速率最低,其平均值为0.98mm/a,与未涂层样品相比,在14天内减少了81%。根据3天MTT结果,使用PCL/2.5%HA涂层可使细胞活性从43%提高到121%。综上,涂覆PCL/2.5%HA纤维的Mg/HA复合材料在生物可吸收植入物方面具有广阔的应用前景。

应变路径对AA1050铝板力学性能、成形极限曲线及织构演化影响的实验研究

实验研究了应变路径变化对AA1050铝合金力学性能、成形性能和成形极限的影响。讨论了以单向、反向和交叉轧制的三种不同方式的应变路径。对比了三种轧制方式在20%和40%轧制比下的晶粒尺寸、硬度、应力-应变曲线和成形极限。结果表明,交叉轧制试样的晶粒尺寸小于其他方式轧制试样的晶粒尺寸;单向和交叉轧制试样的强度和伸长率均高于反向轧制方式的,单向和交叉轧制试样的硬度等于或大于反向轧制试样的;此外,交叉轧制使试样的各向异性减小,R趋近于1。试样的成形极限在交叉轧制方式下明显提高,在40%轧制比下,交叉轧制的FLC_(0)为0.113,单向轧制的FLC_(0)为0.09,反向轧制的FLC_(0)为0.081。单向和反向轧制的成形极限与加载路径的相关。

Severe plastic deformation (SPD) of biodegradable magnesium alloys and composites: A review of developments and prospects

The use of magnesium in orthopedic and cardiovascular applications has been widely attracted by diminishing the risk of abnormal interaction of the implant with the body tissue and eliminating the second surgery to remove it from the body.Nevertheless,the fast degradation rate and generally inhomogeneous corrosion subsequently caused a decline in the mechanical strength of Mg during the healing period.Numerous researches have been conducted on the influences of various severe plastic deformation(SPD)processes on magnesium bioalloys and biocomposites.This paper strives to summarize the various SPD techniques used to achieve magnesium with an ultrafine-grained(UFG)structure.Moreover,the effects of various severe plastic deformation methods on magnesium microstructure,mechanical properties,and corrosion behavior have been discussed.Overall,this review intends to clarify the different potentials of applying SPD processes to the magnesium alloys and composites to augment their usage in biomedical applications.

纳米Al2O3增强颗粒对热锻AZ31B镁合金单轴及高周疲劳性能的影响

研究热锻工艺对AZ31B合金和AZ31B/1.5vol.%Al2O3纳米复合材料在静态和循环加载下的显微组织和力学性能的影响。首先将铸态合金和复合材料在450℃下进行均匀化热处理,然后在450℃下进行开式模锻。结果表明,增强颗粒的存在有利于晶粒细化和改善动态再结晶。锻造工艺能更有效地消除铸态合金工件中的孔隙。与铸态和锻态合金试样相比,锻态复合材料的显微硬度分别提高80%和16%。与锻态合金的相似区域相比,锻态复合材料的极限抗拉强度和最大拉伸应变分别提高45%和23%,极限压缩强度和最大压缩强度分别提高50%和37%。复合材料在低应变区的疲劳寿命提高,而在高应变区的疲劳寿命降低。与AZ31B试样不同,复合材料的拉伸、压缩和高周疲劳行为对施加应变的敏感性较低,这与试样在热锻前后的孔隙率有关。

Effect of stiffeners on crashworthiness of square aluminium columns considering damage evolution

Combining the optimization and FEM technology,crashworthiness of aluminum extrusions was studied for an automobile safety plan.The effects of longitudinal stiffeners on the crushing of stiffened square columns were studied considering the damage evolution.The numerical analysis was carried out by ABAQUS software.Subsequently,the collapse behavior of aluminum extrusion damage was validated by comparing against solution published in literature.Finally,in order to find more efficient and lighter crush absorber and achieving minimum peak crushing force,response surface methodology(RSM) has been applied for optimizing the aluminum extrusion tube.

In vitro corrosion-fatigue behavior of biodegradable Mg/HA composite in simulated body fluid

Magnesium and its composites as biodegradable materials offer especial capabilities to be used as bio-absorbable implants.However,their poor corrosion and fatigue properties in the physiological environment can restrict their applications.In this study,corrosion-fatigue tests have been performed on the extruded magnesium and magnesium/hydroxyapatite(Mg/HA)composites in a high cycle regime.To produce the composites,pure magnesium was reinforced by 2.5 wt.%and 5 wt.%of hydroxyapatite submicron particles using an electromagneticmechanical stirring method and hot extrusion process.The experimental density measurement exhibits that the porosity increases in the extruded samples with more hydroxyapatite particles.To investigate the corrosion and corrosion-fatigue behavior of the specimens,simulated body fluid(SBF)was used during in vitro tests.The results of the potentiodynamic polarization corrosion test show that the composite with 2.5 wt.%of hydroxyapatite(Mg/2.5 wt.%HA)and the pure magnesium specimen exhibit the highest and the lowest corrosion resistance,respectively.Regarding the elemental mapping analysis of the corroded samples,this behavior could be due to the formation of strong phosphorus-calcium based layers on the composite surface.The results obtained from the mechanical tests indicate that Mg/5 wt.%HA offered the highest tensile and compressive yield strengths,as well as the most promising high cycle fatigue behavior.During the corrosionfatigue test,the simultaneous effects of fatigue and corrosion damages led to a similar corrosion-fatigue behavior in both composites.The fracture surfaces of the corrosion-fatigue samples suggest that the cracks are initiated in the corroded regions of the samples surface,which reduces the crack initiation step and subsequently decreases the fatigue life.In comparison with the pure magnesium,both composites exhibit more promising corrosion and corrosion-fatigue behaviors with a significant fatigue life improvement in the physiological environment.

工艺参数对摩擦辅助管应变法加工管组织和力学性能的影响

研究了摩擦辅助管应变(FATS)法对管材组织和力学性能的影响。采用有限元法分析并进行实验测试。用Taguchi设计(ATD)进行分析,改变转速、进给速率和模具角度来进行数值和实验试验。结果表明,提高进给速率和降低转速提高了Zener-Hollomon参数(Z),减小了平均晶粒尺寸,而对模具角度没有显著影响。增加Z值可以减小晶粒尺寸,增强加工样品的流动应力。实验结果表明,具有最大Z值的样品其晶粒尺寸从初始的40μm细化到8μm,其流动应力增加5倍。