Thermomechanical treatments on high strength Al-Zn-Mg(-Cu) alloys

An investigation was carried out to determine the metallurgical properties of Al-Zn-Mg and Al-Zn-Mg-Cu alloy products processed according to newly developed Final Thermomechanical Treatments (FTMT) of T-AHA type. The results show that these cycles can be utilized to produce wrought products of high purity Al-Zn-Mg(-Cu) alloys characterized by equivalent toughness and ductility and much higher strength than conventionally processed commercial purity materials. Based on transmission electron microscopy studies, it was found that such improved behavior of FTMT material is attributable to the superposition of hardening effects, from aging precipitation and from dislocations. Preliminary stress-corrosion and fatigue tests indicate that these properties are not substantially influenced by T-AHA thermomechanical process. Further work is needed in this area, in order to better understand the directions to follow for developing better alloys.     

Enhanced magnetostrictive properties of lightly Pr-doped Fe_(83)Ga_(17) alloys

Fe₈₃Ga₁₇Pr_x alloys,where x=0,0.2,0.4,0.6 and 1.0,were prepared by a non-consumable vacuum arc melting technique under an inert argon gas atmosphere.The crystal structure and surface morphologies of the alloys were studied by X-ray diffraction(XRD) and scanning electron microscopy(SEM),respectively.Local compositional variations were measured by energy dispersive X-ray spectroscopy(EDXS).The magnetostriction coefficients of the alloys were measured by means of a d...     

粉末冶金法制备La_(0.75)Mg_(0.25)Ni_(3.5-x)Mn_x(x=0-0.4)合金及其电化学贮氢性能研究

为了改善稀土系A_2B_7型贮氢合金的电化学贮氢性能,采用粉末冶金方法制备的La_(0.75)Mg_(0.25)Ni_(3.5-x)Mn_x(x=0,0.1,0.2,0.3,0.4)贮氢合金,研究少量Mn替代Ni对合金相结构和电化学性能的影响。结果表明:合金由La Ni5、La2Ni7两相组成,随着Mn含量的增加,两相晶胞逐渐膨胀。Mn的加入能显著改善合金的电化学性能,然而过高的Mn含量会对合金的放电性能带来不利影响。其中La_(0.75)Mg_(0.25)Ni_(3.2)Mn_(0.3)合金电极的最大放电容量为362.3m Ah/g,经过100次循环后容量保持率为69.5%。此外,合金电极的高倍率放电性能、线性极化曲线以及电化学交流阻抗谱的测试均表明合金的电化学动力学性能随着Mn含量的增加先增大而后减小。