Repeated low-velocity impact responses of SiC particle reinforced Al metal-matrix composites

This study aimed to investigate experimentally the repeated low-velocity impact behaviors of SiC reinforced aluminum 6061 metal-matrix composites for different volume fractions and energy levels. In addition, the hardness variations were measured by the Vickers hardness tests from the impacted and impact-free cross-sections of the particle reinforced metal-matrix composites. Low-velocity impact tests were applied to composite samples manufactured by powder metallurgy (in 10, 20, and 30% volume fractions) at two total energy levels (15 and 60 J as single) and in repetitions equal to the sum of these energy levels (5 + 5 + 5 and 20 + 20 + 20 J as repeated). As a result, in increasing the impact number for all volume fractions, the total contact time was shortened and the peak contact force increased, whereas both the permanent central deflection and the absorbed energies reduced. Hence, these variations obtained under repeated impacts (5 + 5 + 5 and 20 + 20 + 20 J) revealed that metal-matrix composites showed a tougher behavior with an increase in the impact numbers from 1st to 3rd, particularly because of the strain hardening effect. Furthermore, an increase in volume fraction from 10 to 30% resulted in an increase in the impact strength under all repeated and single impacts despite changing deformation and damage mechanisms due to increasing the strain hardening effect and particle fractures. The hardness was affected by the volume fraction and increased as the volume fraction increased in both the impacted and impact-free zones. The repeated impact increased the impacted zone hardness more than the single impact for all volume fractions. Additionally, the hardness of the impacted zone under 20 + 20 + 20 J repeated impact was measured as the highest value in the 30% volume fraction. Therefore, metal-matrix composites can behave harder with the strain hardening effect under repeated impacts.     

Fabrication and characterization of in-situ Al3Ni intermetallic and CeO2 particulate-reinforced aluminum matrix composites

Al-xNi-yCeO₂ (x = 6, 10, 15, 20 and y = 0, 5, 10 wt%) composites were produced by a powder metallurgical production route. Powder mixtures of Al, Ni and CeO₂ were fabricated via mechanical alloying (MA) for 4 h in a Spex-type high-energy ball mill. Both the mechanically alloyed (MAed) and non-MAed (as-blended mixtures) powders were pre-compacted in a hydraulic press under 650 MPa and then pressurelessly consolidated at 630 °C for 2 h under an inert atmosphere. The effects of MA process and the amounts of Ni and CeO₂ on the microstructural, mechanical and tribological properties of the sintered composites were determined. Based on the SEM and XRD investigations, the MAed powders illustrated a homogenous structure, comprising flaky particles with smaller crystallite sizes and greater lattice strain. According to the XRD analysis, Ni formed Al–Ni intermetallic compounds in the matrix of sintered composites that act as secondary reinforcement phases. The SEM observations conducted on the MAed samples demonstrated more uniformly and finely distributed Al₃Ni and CeO₂ phases in the microstructure of the MAed samples, unlike the non-MAed ones. The hardness values of sintered composites increased due to the MA process and increasing Ni and CeO₂ amounts, and the hardness value of the MAed Al20Ni–10CeO₂ sample reached 179 HV. The ultimate compressive strength and failure strain of the MAed Al6Ni–10CeO₂ sample were 441 MPa and 11.3%. In the Al20Ni–10CeO₂ sample, the compressive strength and failure strain were 391 MPa and 5.5%, respectively. Additionally, the reciprocating wear test results illustrated that both wear resistance and hardness values of the composites increased as the amounts of Ni and CeO₂ increased, and the Al20Ni–10CeO₂ sample exhibited the highest wear resistance as 0.175 × 10^-3 mm³/Nm.     

臭氧氧化技术在有色金属湿法冶金中的应用研究进展

臭氧是一种氧化性极强、多功能化的绿色氧化剂。本文综述了臭氧氧化技术在有色金属湿法冶金领域的研究进展和应用现状,重点介绍了在贵金属、重金属、稀有金属及轻金属等有色金属湿法冶金领域的应用研究。详细探讨了臭氧的强氧化性对低品位金属矿和难冶金属矿浸出、溶液中低价态金属离子氧化沉淀、溶液净化除杂等方面的作用机理,并对目前面临的问题进行简要叙述,对其在有色金属湿法冶金领域的应用前景进行了展望。     

内蒙古呼伦贝尔早中生代花岗岩的年代学和岩石地球化学研究：对岩石成因和地球动力学机制的制约

微细粒钛铁矿的回收制约着我国攀西地区钛资源的高效开发利用。四川某矿业公司的斜板溢流原矿属辉石、橄榄石混合型钛铁矿，且粒度极细，-19 μm产率为79.22％，其中TiO2分布率为87.54％。研究结果表明，预先采用强磁选可有效消除部分超微细粒钛辉石、橄榄石等易浮杂质对浮选分离的不利影响，磁选精矿通过一次粗选五次精选一次精扫选流程，可获得钛精矿产率为21.85％，TiO2品位为47.44％，回收率为62.89％的良好指标，为矿山高效利用钛资源提供了合理的技术方案。     

石墨烯增强钛基复合材料制备工艺与性能研究

以多层石墨烯为增强体,通过熔炼锻造(MF)和粉末冶金(PM) 2种工艺分别制备出规格为Φ10 mm的石墨烯增强钛基复合材料棒材。石墨烯在凝固过程中以TiC枝晶形态析出,变形后呈细小颗粒,其中Ti和C原子比约为2∶1。石墨烯和球形钛粉经过机械合金化和变形加工,在基体中反应形成薄片层。MF工艺对应的棒材拉伸强度可达476 MPa,延伸率保持在28%; PM工艺对应的棒材拉伸强度可达487 MPa,延伸率保持在30%。PM工艺可形成尺寸较小的薄片状石墨烯增强体,强化作用提升,同时塑性没有显著下降。     

TMCP工艺下Ti-Mg氧化物冶金钢轧态组织性能

摘要：为研究轧制过程中氧化物粒子对母材组织性能的影响，提出了一种只在再结晶区进行轧制的新工艺路线，利用常规冶炼及氧化物冶炼的实验钢分析其轧态显微组织、力学性能及相变过程。结果表明：在新轧制工艺下，氧化物冶金钢母材显微组织由常规的贝氏体板条束变为针状铁素体，其基体具有良好的力学性能，-80℃冲击韧性达149J；热轧工艺下的组织转变分两阶段进行，初期是针状铁素体的形核和晶粒细化，之后贝氏体相变被限制在针状铁素体板条间构成的区域内。     

诱发IAF夹杂物与原晶粒的尺寸匹配关系

 对于氧化物冶金船板钢而言，细小弥散分布的夹杂物会对其原始晶粒产生钉扎和诱发晶内铁素体的双重作用，且研究发现诱发晶内铁素体的夹杂物尺寸与原始奥氏体晶粒尺寸存在一定的匹配关系。围绕上述问题进行了系统的分析研究和数据统计,结果表明，不同晶粒尺寸下，诱发晶内铁素体的夹杂物尺寸与原奥氏体晶粒度间存在近似线性关系，且随着奥氏体晶粒度的增大，诱发晶内铁素体的夹杂物尺寸则相应减小。     

Effect of microwave sintering on the microstructure and mechanical properties of AA7075/B4C/ZrC hybrid nano composite fabricated by powder metallurgy techniques

AA7075 + 6%B4C+3%ZrC nano hybrid composite was successfully fabricated, with nano reinforcements composition in AA7075 alloy selected based on previous investigation, to achieve better mechanical performance. Two different sintering techniques, namely conventional and microwave, were implemented to determine the effect on microstructural and mechanical properties. Microstructural investigation was performed with the help of W-SEM. Tensile, compression, and hardness were measured with the help of UTM and Vickers microhardness machine. Porosity was calculated by using Archimedes principle. It was observed that the added nano ZrC particles formed agglomerates and the B₄C particles were distributed homogenously. Composites processed by microwave sintering showed excellent mechanical properties compared to the conventionally sintered composites. No intermetallic compounds were detected in microwave sintered composites through XRD analysis, indicating strong and clean interface bonds between matrix and reinforcement particles. High strain to fracture value of 12.24% was noted in microwave sintered nano hybrid composite, while it was 6.12% for conventional sintered one. Fractography revealed no peeling action of reinforcements from the matrix material, and the mode of failure was brittle. It was concluded that, while fabricating nano range hybrid composites, the implementation of advanced sintering technique (microwave sintering) with low sintering temperatures and low sintering times with internal heat generations, helps in eliminating defects that may develop because of high surface energies of nano range reinforcements.     

广西玉林胜果寺古代冶铸遗址研究

玉林胜果寺古代冶铸遗址位于广西玉林市兴业县龙安镇杨前村胜果寺附近的丘陵,面积超过2 000m~2。采用扫描电镜及能谱分析(SEM-EDS)、金相和矿相等研究方法,对胜果寺古代冶铸遗址的5个冶金遗物炉渣样品进行成分和显微组织分析检测。结果表明,该遗址为生铁冶铸遗址,炼渣属锰硅铝系高锰炉渣。冶炼产品除供本地铸锅等生产生活用品外,大量运往韶州涔水场浸铜。