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首页> 外文学位 >Processing microstructure-property relationship in aluminum-iron-vanadium-silicon alloys produced by atomized melt deposition.
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Processing microstructure-property relationship in aluminum-iron-vanadium-silicon alloys produced by atomized melt deposition.

机译：雾化熔融沉积生产的铝-铁-钒-硅合金的加工组织与性能的关系。

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A mathematical model was developed for the atomized melt deposition process in which the liquid metal stream is disintegrated into fine droplets by high speed inert gas and the droplets are deposited directly onto the substrate of required geometry. The numerical model determines the droplet velocity, droplet thermal history, cooling rates of droplets, volume fraction solid in the spray of droplets before deposition and thermal history of the deposit. The solidification heat transfer phenomena taking place during atomized melt deposition was analyzed using a finite difference method based on enthalpy formulation. The numerical model was validated by measuring average spray temperature by oil calorimetry and thermal history of the deposit by continuous monitoring of deposit temperatures. Dispersion strengthened Al-8.5%Fe-1.2%V-1.7% Si alloy, used for high temperature applications was used for model validation and processing-microstructure-property correlations. The predicted thermal history of the deposit and average spray temperature were in good agreement with the corresponding measured temperatures. The extent of undercooling and the rate of droplet solidification were correlated with process parameters such as melt superheat, metal/gas flow rates and melt stream diameter. The size distribution and morphology of silicide dispersoids were used to estimate the cooling rate as functions of process parameters. The tensile properties at 25-425{dollar}spcircrm C{dollar}, fatigue crack growth resistance and fracture toughness at {dollar}25spcircrm C{dollar} of these alloys produced with wide variations in dispersoids size and grain size were determined and were correlated with microstructures. The room temperature fatigue crack growth rates and fracture toughness were evaluated for different crack plane orientations of the same alloy produced by planar flow casting and were compared with those of the alloy produced by atomized melt deposition process.; Deformation characteristics of the alloy processed by planar flow casting was studied by examining the stress strain behavior in tension at 25-420{dollar}spcircrm C{dollar} and the stress strain behavior in compression at {dollar}25spcircrm C{dollar} and hardness tests. The as processed planar flow cast alloy showed non linear elastic behavior, flow softening, yield drop, low uniform and total elongation, serrated yielding, stress relaxation, and anomalous strain rate dependence of ductility. The results indicated that greater dynamic recovery due to fine grains ({dollar}<{dollar}0.3 {dollar}murm m){dollar} and an essentially pure aluminum matrix in the as processed planar flow cast alloy contribute to the observed deformation characteristics. Corroborative evidence for recovery processes was obtained by differential scanning calorimetry and hardness measurements of cold rolled and annealed samples.
机译：建立了雾化熔体沉积过程的数学模型，其中液态金属流通过高速惰性气体分解成细小液滴，并将这些液滴直接沉积到所需几何形状的基材上。数值模型确定了液滴的速度，液滴的热历史，液滴的冷却速率，在沉积之前液滴喷雾中的固体体积分数以及沉积物的热历史。使用基于焓公式的有限差分法分析了雾化熔体沉积过程中发生的凝固传热现象。通过用油量热法测量平均喷雾温度和通过连续监测沉积物温度来测量沉积物的热历史来验证数值模型。用于高温应用的弥散增强的Al-8.5％Fe-1.2％V-1.7％Si合金用于模型验证和加工-微观结构-性能相关性。沉积物的预计热历史和平均喷涂温度与相应的测得温度高度吻合。过冷程度和液滴凝固速率与工艺参数如熔体过热，金属/气体流速和熔体流直径相关。硅化物分散体的尺寸分布和形态被用来估计冷却速率与工艺参数的关系。测定了在弥散体尺寸和晶粒尺寸上有很大差异的这些合金在25-425 {dollar} spcircrm C {dollar}时的拉伸性能，在25dolph 25spcircrm C {dollar}时的抗疲劳裂纹扩展性能和断裂韧性。具有微结构。对通过平面流铸生产的同一合金在不同裂纹平面取向下的室温疲劳裂纹扩展速率和断裂韧性进行了评估，并将其与通过雾化熔融沉积工艺生产的合金进行比较。通过研究在25-420 {dolph} spcircrm C {dollar时的拉伸应力应变行为和在{dollar} 25spcircrm C {dollar}时的压缩应力应变行为和硬度，研究了平面流延铸造合金的变形特性。测试。加工后的平面流动铸造合金表现出非线性弹性，流动软化，屈服下降，均匀度和总伸长率低，锯齿状屈服，应力松弛和延展性的异常应变率依赖性。结果表明，在加工后的平面流铸合金中，由于细晶粒（{0.3} {m} m）{美元}和基本上纯的铝基体，导致更大的动态恢复。通过差示扫描量热法和冷轧和退火样品的硬度测量获得了恢复过程的确凿证据。

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