应变硬化的Al—Mg合金

本文介绍了含4.4—10％Mg、强度水平比退火状态至少提高40％且实质上没有剥落腐蚀敏感性的应变硬化铝合金板材。这种工艺包括根据不同的镁含量在最低为420°—650°F左右的温度下轧制以生产出应变硬化的板材,并且以特殊的控制速度进行冷却。     

Mg13Al14和Mg17Al12中间合金的第一性原理研究

Mg-Al合金具有密度小、刚度好、强度质量比极佳、可铸性以及延展性良好等优点,可作为一种性能优异的轻量级结构材料。Mg_(17)Al_(12)作为其中的中间合金,具有阻碍位错运动来强化晶界的重要作用。本工作采用第一性原理方法,系统研究了Mg_(13)Al_(14)和Mg_(17)Al_(12)两种中间合金的晶体结构、电子结构及力学性能。研究结果表明:Mg_(13)Al_(14)的原胞结构不具有热力学稳定性,而Mg_(13)Al_(14)初胞结构热力学稳定,且稳定性高于Mg_(17)Al_(12);通过电子结构分析发现,Mg_(13)Al_(14)和Mg_(17)Al_(12)均具有很强的金属性,且Mg_(17)Al_(12)的离子性略强于Mg_(13)Al_(14),因此Mg_(17)Al_(12)具有更高的结构稳定性;通过力学参数计算,可以得出二者的初胞均具有良好的力学稳定性,而Mg_(13)Al_(14)的原胞不具有力学稳定性。其中Mg_(13)Al_(14)表现为延性材料,Mg_(17)Al_(12)表现为脆性材料; Mg_(13)Al_(14)初胞的可塑性更好,抵抗剪切形变的能力强于Mg_(17)Al_(12); Mg_(17)Al_(12)的刚性更高,抗塑性变形能力强于Mg_(13)Al_(14); Mg_(13)Al_(14)和Mg_(17)Al_(12)均表现为弹性各向异性;对于Mg-Al合金,中间合金初胞结构的Mg_(13)Al_(14)的综合力学性能优于Mg_(17)Al_(12),但原胞的热力学稳定性较差,与Mg_(17)Al_(12)相比不利于提升Mg-Al的热稳定性。     

Formation of Al3Ti/Mg composite by powder metallurgy of Mg–Al–Ti system

Abstract

An in situ titanium trialuminide (Al₃Ti)-particle-reinforced magnesium matrix composite has been successfully fabricated by the powder metallurgy of a Mg–Al–Ti system. The reaction processes and formation mechanism for synthesizing the composite were studied by differential scanning calorimetry (DSC), x-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Al₃Ti particles are found to be synthesized in situ in the Mg alloy matrix. During the reaction sintering of the Mg–Al–Ti system, Al₃Ti particles are formed through the reaction of liquid Al with as-dissolved Ti around the Ti particles. The formed intermetallic particles accumulate at the original sites of the Ti particles. As sintering time increases, the accumulated intermetallic particles disperse and reach a relatively homogeneous distribution in the matrix. It is found that the reaction process of the Mg–Al–Ti system is almost the same as that of the Al–Ti system. Mg also acts as a catalytic agent and a diluent in the reactions and shifts the reactions of Al and Ti to lower temperatures. An additional amount of Al is required for eliminating residual Ti and solid-solution strengthening of the Mg matrix.     

Mg/Al波纹复合板抗冲击性能研究

目的 比对波纹轧制结构和平面复合结构的Mg/Al复合板抗冲击性能与吸能机制.方法 采用波纹辊轧制工艺制备Mg/Al复合板,使用半球形铝合金弹丸对传统平面复合板与波纹复合板进行不同速度下的冲击试验研究,并对比分析2种复合板的损伤机理,探明波纹结构对复合板抗冲击性能的影响.结果 Mg/Al平面复合板抗半球形弹丸冲击的吸能机制主要是通过靶板的塑性变形、剪切破坏、拉伸断裂、分层破坏和弹丸与靶板间摩擦等形式来吸收能量.波纹复合板对冲击能量的吸收主要依赖靶板的局部塑性变形、沿着波纹方向的开裂、结合界面的分层以及弹丸与靶板间的摩擦耗能.结论 当冲击速度低于弹道极限速度时,波纹复合板的抗冲击性能优于平面复合板,高于弹道极限速度时,2种复合板的抗冲击性能和耗能程度相当.     

Thermal properties of Mg–Li and Mg–Li–Al alloys

Abstract

The present work is a study of the thermal properties of Mg–xLi–y Al with x= 4, 8 and 12 wt-% and y= 0, 3 and 5 wt-% as a function of temperature in the range 20–375°C. The thermal diffusivity and coefficient of thermal expansion (CTE) have been measured and the thermal conductivity calculated. The thermal diffusivity of all alloys decreases with an increasing content of lithium. The CTE of the single phase alloys Mg–4Li and Mg–12Li has a linear character, and the CTE of Mg–12Li is higher than that of Mg–4Li. The influence of thermal stresses in the two phase alloy Mg–8Li is perceptible in terms of temperature dependence of the CTE. In Mg–4Li–3Al and Mg–4Li–5Al, an influence of the solution of AlLi phase on all the studied thermal properties has been found.     

Corrosion Properties of Oxide Ceramic Coatings Based on Alloys of the Al–Cu–Mg and Al–Mg Systems

Materials Science - By the methods of electrochemical impedance spectroscopy and potentiodynamic methods, we estimate the corrosion resistance of oxide ceramic coatings obtained on...     

Al—Li—Mg合金的新制法

外刊报道了研究开发均质、力学性能优异的Al/Li/Mg合金新制法。这种合金经过热挤压后施行时效处理,弹性系数大,密度小,组织细化。最重要的是没有象普通合金那样,氧化物和碳化物在晶界析出后产生晶界裂纹。     

Grain refinement of Mg–Al alloys with Al4C3–SiC/Al master alloy

A novel Al₄C₃–SiC/Al master alloy for grain refinement of Mg–Al–Zn alloys has been developed in the present work. X-ray diffraction (XRD) and electron probe microanalysis (EPMA) results show the existence of Al₄C₃ and SiC particles in this master alloy. The master alloy presents good grain refining efficiency on both AZ31 and AZ63 alloys, but little effect on AZ91 alloy. After addition of 0.5 wt.% Al₄C₃–SiC/Al master alloy, the average grain size of AZ31 and AZ63 decreased dramatically from 1300 to 225 μm, and from 300 to 200 μm, respectively. However, no further refinement of grain size was achieved with additional amount of Al₄C₃–SiC/Al master alloy exceeding 0.5 wt.% for both AZ31 and AZ63 alloys in the present investigation. Duplex phase of Al₄C₃ and SiC was found to be located at the grain center of α-Mg and is proposed to be the nucleating agent during solidification of α-Mg.