Effect of heat treatment on microstructure and properties of hot-extruded nickel-aluminum bronze

The effect of heat treatment on the microstructure and properties of a hot-extruded nickel-aluminum bronze was investigated. Experimental materials were heat treated through different processes, including quenching, normalizing, aging and annealing, and their microstructure, corrosion resistance and mechanical properties were characterized. It is found that quenching causes all β phase transformed into β phase, however, normalizing causes β phase transformed into β α and κ phases. When the quenched sample is aged, fine phase is precipitated from the as-quenched microstructure of β＇ phase. Annealing causes the transformation of β into a and κ phases. The results of mechanical property tests show that quenching, normalizing and aging improve the tensile strength and hardness of the experimental material, with a corresponding fall in elongation. Annealing raises the elongation but reduces the tensile strength and hardness. Furthermore, corrosion resistance of nickel-aluminum bronze ranks from worse to better in the following order： aged, quenched, normalized, hot-extruded and annealed. However, with the exposure time of corrosion test increasing, the difference of average corrosion rate between those nickel-aluminum bronzes tums small.     

Influence of heat treatment on tribological behaviors of novel wrought aluminum bronze

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双流浇注连续铸造过程浓度分布数值模拟

本文初步建立了双流浇注连续铸造圆柱坯的浓度分布数值模拟的数学模型,分析了不同工艺参数下的浓度场分布特征,包括拉坯速度、内导管插入深度和内浇包温度.并比较了内浇包熔体含量的模拟结果与铸坯横截面上Cu含量的试验结果,两者基本吻合.     

半连续铸造制备2024/3003梯度材料的研究

采用双流浇注半连续铸造方法制备了2024/3003铝合金梯度材料。研究了节流孔径和内浇包熔体温度两个工艺参数对铸件的成分分布，宏观组织和洛氏硬度的影响，结果表明，在保证铸造过程顺利进行的前提下，适当增大节流孔径和升高内浇包熔体温度都能增加铸件中内部合金的体积分数。合金的成分、宏观组织和力学性能之间的对应关系说明双流浇注半连续铸造方法制备2024/3003多元铝合金梯度材料是可行的。     

Rapidly solidified hypereutectic Al-Si alloys prepared by powder hot extrusion

Rapidly solidified hypereutectic Al-Si alloys were prepared by powder hot extrusion.By eliminating vacuum degassing procedure.the fabrication routine was simplified.The tensile fracture mechanisms at room temperature and elevated temperature were investigated by SEM fractography.Compared with KS282 casting material,the tensile strength of rapidly solidified Al-Si alloy is greatly improved due to silicon particles refining while its density and coefficient of thermal expansion are lower.than those of KS282.The wear resistance of RS AlSi is better than that of KS282.     

Effects of RE on Microstructures and Mechanical Properties of Hot-Extruded AZ31 Magnesium Alloy

Effects of rare earth (RE) additions on microstructure and mechanical properties of the wrought AZ31 magnesium alloy were investigated. The results show that, by adding 0.3%, 0.6% and 1.0% RE elements, the as-cast microstructure can be refined, and the as-cast alloys‘ elongation and tensile strength can be improved. After extrusion, the alloy with 0.3 % and 0.6% RE additions obtain a finer microstructure and the best mechanical properties, but the alloy with 1.0% RE addition has the coarse A1-RE compound particles in grain boundaries which decreased elongation and tensile properties. Usually, Rare earth (RE) elements were used to improve the creep properties of aluminium-containing magnesium pressure die cast alloys at elevated temperatures. In this paper, it is also found that the high temperature strength of extruded materials can be increased by RE elements additions.     

Microstructure and mechanical property of 2024／3003 gradient aluminum alloy

2024/3003 gradient aluminum alloy was prepared by semi-continuous casting using double-stream-pou-ring technique. The microstructures of the as-cast, pressed and heat-treated alloys were analyzed by scanning elec-tron microscope and transmission electron microscope. And the mechanical properties of the alloy in pressed and heat-treated states were studied. The results show that the ingots with diameter of 65 mm and external thickness about 5.5 mm are obtained when the temperatures of the melt in the internal and external ladles are 1 023 and 1 003 K, respectively, and the nozzle diameter is 2.0 mm. The microstructures of the as-cast alloy consist of α(AI) θ(CuAl2)q S(Al2CuMg) in the internal region and α(Al) MnAl6 in the external region. The phases found in the internal and external layers coexist in the transition zone. The transition layer is maintained after plastic deformation and heat treatment of the alloy. The tensile strength, yield strength and elongation of the alloy are 300 MPa,132 MPa and 16.0%, respectively, after T6 treatment. The tensile and yield strength are increased by 150.0% and 94.1%, respectively, compared with that of 3003 aluminum alloy. The maximum hardness in the internal region of 2024/3003 gradient aluminum alloy can be increased from HRF 55 in the pressed state to HRF 70 in the heat-treated state.     

超声振动和挤压压力作用下含0.6%Fe Al-Cu合金的 显微组织和力学性能

采用光学显微镜（OM）、扫描电子显微镜（SEM）和能谱（EDX）、图像统计以及拉伸试验等手段,研究超声振动（UT）和挤压压力（P）联合作用对铸态Al-5.0Cu-0.6Mn-0.6Fe合金显微组织和力学性能的影响。结果表明,P + UT工艺对处理和α-Al、富铁相和Al2Cu的形貌和尺寸有显著影响,富铁的金属间化合物,促进α-Al形貌由树枝状向球状转变,降低了α-AlAl6(FeMn)和Al2Cu相的尺寸。P + UT工艺有利于减少压力作用下经常出现的双峰组织和晶界偏析。P + UT工艺下得到最好的铸态力学性能：抗拉强度（UTS）：268 MPa,屈服强度（YS）：192 MPa,伸长率：17.1%,分别比重力铸造的合金高为64%、59%和307%。     

不锈钢网增强锆基非晶复合材料的压铸制备及力学性能研究

全程真空压铸技术的快速发展为大块非晶合金的工业化应用提供了可能,受到了广泛关注。但是,非晶合金的室温脆性限制了压铸结构件在一些关键领域的应用。本论文利用压铸工艺高速充型及高压凝固的特性,通过在Vit1锆基非晶合金中引入304不锈钢网叠层焊接制造的骨架,成功制备出了不同体积分数晶态相增强的非晶复合材料,并系统研究了不锈钢网体积分数对力学性能的影响。研究结果表明,不锈钢网在非晶基体中均匀分布,与非晶合金存在冶金界面结合。力学性能测试显示,随着不锈钢编织网的引入,室温脆性的压铸Vit1块体金属玻璃的塑性得到了显著提升。随着不锈钢网目数增大(对应晶态相体积分数增大),非晶复合材料的塑性呈增大的趋势,但是,当目数超过200时,过细的孔洞会导致骨架局部区域无法填充,恶化性能。当晶态相的体积分数为53.7％时,断裂应变达到最大值,约为10％左右,其值高于传统不锈钢纤维增韧的Zr基非晶复合材料。韧化机制分析表明,压铸非晶合金出现脆-延性转变的根本原因是不锈钢网对剪切带扩展进行高效抑制,促进剪切带的增殖和萌生,减少宏观塑性变形的局域化。本研究为非晶复合材料的结构设计提供了新的思路,对于促进非晶合金的更广泛应用具有重要的工程价值。     

基于热压缩的Cu-15Ni-8Sn合金动态再结晶行为研究

目的 获得Cu-15Ni-8Sn合金动态再结晶临界模型,描述热变形参数对动态再结晶晶粒尺寸的影响规律.方法 基于前期通过Gleeble-3500热模拟机得到的热压缩实验数据,分析Cu-15Ni-8Sn合金在不同热变形参数下的再结晶晶粒尺寸及流变应力数据,采用线性回归拟合等方式建立动态再结晶模型,并利用数值模拟与实验相结...