Bi对Al-30% Mg_2Si复合材料组织和性能的影响

为了研究铋(Bi)对Al-30%Mg2Si复合材料显微组织和力学性能的影响,利用原位内生工艺制备了Al-30%Mg2Si复合材料,并加入不同量的Bi对其细化变质.利用扫描电镜进行显微组织观察,并利用布氏硬度计和液压式万能试验机进行力学性能测试.试验结果显示,稀土Bi的质量分数由0%增加至5%时,初生相Mg2Si的平均晶粒尺寸先减小后变大,而抗拉强度、硬度和伸长率则先提高后减小;当Bi加入量约为3%时,初生相Mg2Si显微组织细化效果最为明显,综合力学性能最好.     

镁合金晶粒细化剂研发现状及展望

阐述了目前镁合金液态下几种晶粒细化剂如含碳细化剂、硼化系合金细化剂、稀土元素或混合稀土晶粒细化剂、含Zr元素合金以及其它合金元素如Ca、Sr、Ti等晶粒细化剂的研究现状及最新进展,并对液态下镁合金晶粒细化机理进行分析,针对性提出镁合金细化剂研制的几种思路,对今后的研制方向进行了展望.     

Effect of ECAP Pass Number on Mechanical Properties of 2Al2 Al Alloy

2Al2 Al alloy was suffered from equal-channel angular pressing(ECAP)in this experiment. The influence of ECAP pass number on ultimate strength(UTS),hardness and elongation was studied.The results show that during ECAP the number of sample passing through the channels is very important for mechanical properties and microstructure refinement.ECAP not only increases their plasticity and hardness but also leads to refined grain.But the elongation reduces from 17.5% to 11.8 % after 1 pass ECAP,then almost tends to be unchanged with the increasing of pass number.The value of ultimate strength of 2Al2 Al alloy increases by 135%,hardness by 51%,and ultra fine grains of about 200 nm can be observed after 8 passes.     

Influence of Mg2N2 powder on microstructures and mechanical properties of AZ31 Mg alloy

In order to obtain an effective and reliable grain refiner for Mg-Al alloys, 1% (mass fraction) Mg3N2 was added into AZ31 Mg alloy. The microstructures of the Mg alloys were studied by optical microscopy, scan electron microscopy and X-ray energy dispersive spectroscopy, and the mechanical properties were determined. The results show that adding a small amount of Mg3N2 to AZ31 Mg alloy can refine the grain size from 103 to 58 μm. The ultimate tensile strength and elongation of AZ31 Mg alloy are 174.1MPa and 8.3%, respectively. After the addition of 1% Mg3N2, the ultimate tensile strength and elongation of AZ31 Mg alloy are increased up to 198.7 MPa and 11.8%, respectively. The grain refinement mechanism is that AIN is formed after Mg3N2 is added.Both A1N and Mg phases are of HCP lattice structure, and the disregistry between Mg phases and AIN along (0001)Mg//(0001)AlN is 3.04%, which is very effective for heterogeneous nucleation.     

MgCO_3对AZ31镁合金晶粒的细化

研究了MgCO3对AZ31镁合金凝固组织的影响。结果表明:随着MgCO3的增加,合金中的β-Mg17Al12相由晶内分布变为晶间分布。在AZ31中添加0.6%的MgCO3,于760℃时保温10min,细化效果最佳。α-Mg晶粒的尺寸由基体合金的570μm降至100μm,降低幅度约为82.5%,抗拉强度提高了57.9%,延伸率约提高了11.1%。通过能谱分析,结合能计算及自由能计算证实,细化机理是MgCO3反应后生成的部分Al4C3质点作为异质核心细化晶粒。多余的Al4C3质点钉扎晶界阻碍晶粒长大。Al元素随固/液界面前沿被快速推至晶界,生成沿晶界生长的β-Mg17Al12相,起到进一步固定晶界的作用。合金元素的分布均有改变。     

Al-Ti-C中间合金的制造及其细化效果的研究

含有TiC质点的中间合金可以作为铝及铝合金的晶粒细化剂。在试验室内用真空感应炉和电阻炉能够熔炼出Al-Ti-C中间合金。用试制的铸态Al-Ti-C中间合金对99.7％Al进行晶粒细化处理,与商品的丝状Al-Ti-B中间合金比较,有相似的细化效果。这项研究表明,Al-Ti-C三元中间合金是有应用价值的。     

Effect of ECAP pass number on mechanical properties of 2A12 Al alloy

2A12 Al alloy was suffered from equal-channel angular pressing（ECAP） in this experiment. The influence of ECAP pass number on ultimate strength（UTS）, hardness and elongation was studied. The results show that during ECAP the number of sample passing through the channels is very important for mechanical properties and microstructure refinement. ECAP not only increases their plasticity and hardness but also leads to refined grain. But the elongation reduces from 17.5% tol 1.8 % after 1 pass ECAP, then almost tends to be unchanged with the increasing of pass number. The value of ultimate strength of 2A12 Al alloy increases by 135%, hardness by 51%, and ultra fine grains of about 200 nm can be observed after 8 passes.     

Three dimensional microstructures and wear resistance of Al-Bi immiscible alloys with different grain refiners

The three dimensional(3D) microstructures of Al-Bi alloys with different grain refiners(Al-5Ti-B, Al-3B and Al-3Ti) have been studied using synchrotron X-ray microtomography. The relationships between the microstructures and the corresponding wear behavior are verified through the friction and wear tests. The worn surfaces of the samples with grain refiners tested under 15 and 60 N loads are analyzed using Scanning Electron Microscopy(SEM). The results indicate that the addition of grain refiners is beneficial to the size and distribution of the Bi-rich particles in Al-Bi alloys. Compared with Al-5Ti-B and Al-3B grain refiners, the Bi-rich particles are more uniformly distributed and spherical with finer size with the addition of Al-3Ti grain refiner. The refinement renders the Al-20wt%Bi alloy refined by Al-3Ti the superior wear resistance with respect to those refined by Al-5Ti-B and Al-3B grain refiners, corresponding to the microstructures with fine and uniformly distributed Bi-rich particles in the Al matrix.     

Instability of TiC and TiAl3 compounds in Al-10Mg and Al-5Cu alloys by addition of Al-Ti-C master alloy

The performance of Al-Ti-C master alloy in refining Al-10Mg and Al-5Cu alloys was studied by using electron probe micro-analyzer （EPMA） and X-ray diffractometer （XRD） analysis. The results indicate that there are obvious fading phenomena in both Al-10Mg and Al-5Cu alloys with the addition of Al-5Ti-0.4C refiner which contains TiC and TiAl3 compounds. Mg element has no influence on the stability of TiC and TiAl3, while TiC particles in Al-10Mg alloy react with Al to form Al4C3 particles, resulting in the refinement fading. However, TiC particles are relatively stable in Al-5Cu alloy, while TiAl3 phase reacts with Al2Cu to produce a new phase Ti（Al, Cu）2, which is responsible for the refinement fading in Al-5Cu alloy. These indicate that the refinement fading will not occur only when both the TiC particles and TiAl3 compound of Al-Ti-C refiner are stable in Al alloys.     

Preparation and mechanical properties of β-SiC nanoparticle reinforced aluminum matrix composite by a multi-step powder metallurgy process

β-SiC nanoparticle reinforced A1 matrix （nano-SiCp/A1） composite was prepared by a multi- step powder metallurgy strategy including presureless sintering, hot compacting process and hot extrusion. The microstructures of the as-prepared composites were observed by scanning electronic microscopy （SEM）, and the mechanical properties were characterized by tensile strength measurement and Brinell hardness test. The experimental results revealed that the tensile strength of the composite with the addition of 5wt%/3-SIC nanoprtieles could be increased to 215 MPa, increasing by 110% compared with pure A1 matrix. Comparative experiments reflected that theβ-SIC nanoprticles showed significant reinforcement effect than traditional a-SiC micro-sized particles. The preparation process and sintering procedure were investigated to develop a cost effective preparation strategy to fabricate nano-SiCp/A1 composite.     

金属锆(Zr)对铸造镁锌合金的组织与性能的影响

以ZMgZn4合金为基础,分别加入质量分数为0.3%,0.6%,0.9%的Zr以细化镁锌合金的晶粒.对试验材料观察了金相组织,并且对试验材料进行了拉伸试验及硬度测试,比较其力学性能.研究表明,在加入变质剂Zr后,镁锌合金的晶粒明显细化,力学性能得到提高.其中加入锌的质量分数为0.6%的试样其组织细小、均匀、致密,细化效果最好,力学性能提高最明显.     

Al2O3/(W, Ti)C纳米复合陶瓷材料的力学性能与强韧化机理

采用纳米和亚微米级的α-Al₂O₃,以及微米级的(W,Ti)C粉体为原料,制备了Al₂O₃/(W,Ti)C纳米复合陶瓷材料.在基体Al₂O₃含有体积分数为11%的纳米Al₂O₃时复合材料的抗弯强度和断裂韧性达到最优,其抗弯强度、断裂韧性和硬度分别为840MPa,6.55MPa·m^1/2和20.1GPa.TEM实验表明,纳米颗粒的加入明显抑止了基体晶粒的长大,形成了典型的骨架结构,材料的断裂方式为沿晶断裂和穿晶断裂的混合.内晶型和晶间型第二相颗粒产生的残余应力场、断裂模式的改变和晶粒细化强化促进了复合材料抗弯强度和断裂韧性的提高.     

(TiB_2+SiC_p)/ZL101复合材料组份优化及其力学性能

为了确定(TiB2+SiCp)/ZL101复合材料的最佳成分,通过采用正交实验分析方法,研究复合材料的制备工艺,测试了复合材料的力学性能,并对该材料进行了显微金相分析和透射电子显微分析.结果表明,复合材料经过热处理后,抗拉强度、布氏硬度分别较基体合金ZL101提高了21.4%、49.3%;热膨胀系数较基体合金降低了14.1%;热处理后,复合材料中的共晶硅以粒状形态均匀分布于基体中;复合材料中增强相TiB2为粒状,SiC粒子为多边形尖角块状,两相较均匀分布于基体晶粒内部,且与-αAl的界面结合良好.     

Ce对Al-15%Mg_2Si复合材料组织和性能的影响

为了研究Ce元素对Al-15%Mg_2Si复合材料微观组织和力学性能的影响,利用原位内生工艺制备了Al-15%Mg_2Si复合材料,并加入不同质量分数的Ce元素对复合材料进行细化变质.利用扫描电子显微镜进行微观组织观察,利用布氏硬度计和液压万能试验机进行力学性能测试.结果表明,添加Ce元素后Mg_2Si相以块状和粒状形态存在于Al基体中,随着Ce元素质量分数的增加,初生Mg_2Si相得到细化,其力学性能呈现先增大后减小的趋势.当Ce元素的质量分数为0.6%时,初生Mg_2Si相的细化效果最好,其力学性能最佳.     

Si和Al对机械合金化合成Ti3SiC2的影响

采用3Ti／Si／2C单质粉体为原料,进行机械合金化,以合成Ti3SiC2粉体。研究了Al和过量Si对机械合金化合成Ti3SiC2的影响。研究结果表明,机械合金化单质混合粉体,会诱发自蔓延反应。反应后产生大量坚硬的颗粒状产物。机械合金化3Ti／Si／2C粉体,会产生组成相为TiC、Ti3SiC2、TiSi2和Ti5Si3的粉体与颗粒产物。添过量Si并不会促进机械合金化反应合成Ti3SiC2。添适量Al可消除硅化物,明显促进反应合成Ti3SiC2。采用3Ti／Si／2C／0．15Al粉体作原料时,颗粒产物中Ti3SiC2含量最高,为92．8wt％;而采用3Ti／Si／2C／0．20Al粉体作原料时,粉体产物中Ti3SiC2含量最高,为61．9wt％。     

Sr+B联合处理对Al-Si合金组织的影响

采用制备的Al-Sr-B中间合金作为晶粒细化变质剂,观察不同Sr,B含量时Al-Si合金中枝晶和共晶Si形态与大小的变化,考察了Sr,B间的交互作用。研究发现Al-Sr-B中间合金对近共晶Al-Si合金具有很好的细化变质效果。     

Influence of Mg3N2 powder on microstructures and mechanical properties of AZ31 Mg alloy

In order to obtain an effective and reliable grain refiner for Mg-Al alloys, 1% （mass fraction） Mg3N2 was added into AZ31 Mg alloy. The microstructures of the Mg alloys were studied by optical microscopy, scan electron microscopy and X-ray energy dispersive spectroscopy, and the mechanical properties were determined. The results show that adding a small amount of Mg3N2 to AZ31 Mg alloy can refine the grain size from 103 to 58 μm. The ultimate tensile strength and elongation of AZ31 Mg alloy are 174.1MPa and 8.3%, respectively. After the addition of 1% Mg3N2, the ultimate tensile strength and elongation of AZ31 Mg alloy are increased up to 198.7 MPa and 11.8%, respectively. The grain refinement mechanism is that AIN is formed after Mg3N2 is added. Both AIN and Mg phases are of HCP lattice structure, and the disregistry between Mg phases and AIN along （0001）Mg//（0001）AIN is 3.04%, which is very effective for heterogeneous nucleation.     

Squeeze casting of Al-Cu alloy

In order to use the cast method to replace forge method in producing the load-bearing wheel used in certain heavy duty vehicle, simplified and reduced size load-bearing wheels were squeeze cast and studied using Al-Cu alloy. Tensile properties, hardness, microstructures and morphologies of the squeeze-cast wheels were investigated. The results show that the finer microstructure, higher density, strength, toughness and hardness were achieved through the squeeze casting. Ultimate tensile strength of 428 MPa, yield strength of 360 MPa, elongation of 13.1% were achieved for T5 heat-treated squeeze-cast wheels. The Brinell hardness of squeeze-cast wheels is from HB 120 to HB 137.     

Al-Ti-C grain refiner made by ultrasonic levitation

An electrostrictive uniaxial ultrasonic levitation reaction system was designed to perform TiC synthesis reaction by suspending graphite powder in Al-3Ti melt and an Al-3Ti-0.15C grain refiner alloy was obtained. The results show that sound pressure node in which graphite suspends is formed in the melt between radiation block and reflecting board by ultrasonic and TiAl3 particles congregate around C powder. Meanwhile, due to ultrasonic cavitation, dissolved TiAl3 provides better surface condition for the synthesis reaction of TiC. The reaction route is that C and dissolved Ti react to form TiC. Ultrasonic cavitation has a thermal activation effect on TiC particles and Al-3Ti-0.15C refiner has excellent microstructural refining effect on α-Al.