7A09-T6高强铝合金流体连接器的开裂原因

通过裂纹宏观和微观形貌观察、能谱检测以及理论计算,对7A09-T6高强铝合金流体连接器开裂原因进行了分析。结果表明:裂纹在流体连接器壳体口部萌生,并沿轴向往根部扩展,贯穿壁厚,开裂类型为应力腐蚀开裂,其原因是7A09-T6高强铝合金为应力腐蚀敏感材料,采用的硬质阳极氧化工艺引入了腐蚀介质S元素,并且连接器处于拉应力和潮湿环境。

基于声发射的高体积分数碳化硅颗粒铝基复合材料切削刀具效能评估

为评估加工高体积分数碳化硅颗粒铝基复合材料时切削刀具的极限效能,采用声发射信号作为硬质合金刀具、氮化硼涂层刀具、聚晶金刚石刀具在不同工况下的磨损在线监测信号,通过试验绘制声发射信号随刀具磨损的变化曲线,明确刀具磨损随时间变化的规律,确定刀具的极限效能,同时借助扫描电镜观测刀具磨损形态和刃口磨损特征尺寸。研究结果表明,采用声发射信号作为刀具磨损监测信号评估刀具极限效能的方法可行,声发射信号不再出现明显能量波动的时刻达到刀具的极限寿命。加工高体积分数碳化硅颗粒铝基复合材料时,硬质合金刀具切削性能最差,氮化硼涂层刀具切削性能较好,聚晶金刚石刀具切削性能最优。采用氮化硼涂层刀具加工高体积分数碳化硅颗粒铝基复合材料时,建议切削参数为转速2500 r/min、进给速度200 mm/min、切削深度0.5 mm。采用聚晶金刚石刀具加工高体积分数碳化硅颗粒铝基复合材料时,建议切削参数为转速3000 r/min、进给速度300 mm/min、切削深度0.3 mm。

激光封焊T/R组件机械铣削开盖与新盖板适配研究

阐述了激光封焊T/R组件机械铣削开盖工艺及其关键控制点。该工艺实现了开盖过程可控性和质量可靠性,保证了开盖后壳体的尺寸精度一致性及其与新盖板适配的稳定性,且有效避免多余物落入壳体内。并对新盖板与开盖壳体的配合提出适配性要求:当壳体壁厚t≤0.2 mm时,局部最大间隙δ≤0.02 mm;当0.2 mm<壳体壁厚t≤1.5 mm时,局部最大间隙δ≤0.07 mm;当1.5 mm<壳体壁厚t≤2.0 mm时,局部最大间隙δ≤0.10 mm。通过试验验证了开盖-再封盖的工艺可行性,更好地适应组件的研制和生产需求变化。

Fatigue behavior of press hardened Al-Si coated high strength steel

The fatigue behavior of press hardened Al-Si coated high strength steel has been investigated,and the fatigue strength turns out to be about 1 000 MPa.Surface morphology of fractured and non-fractured specimen has been observed,and the coating shows significant influence on the fatigue behavior.The difference of elastic modulus between coating and substrate led to the main cracks perpendicular to the loading direction.The coating close to fracture exfoliated thinly,while the coating far away from the fracture kept integrated.Though the specimen was polished to obtain high surface quality,3 types of cracks occurred during the fatigue test.What’s more,inclusion particles were proved to play a crucial role in causing these cracks.

Enhancing ductility of the Al-Si coating on hot stamping steel by controlling the Fe-Al phase transformation during austenitization

In this study, austenitizing heat treatment before hot stamping of Al-10% Si coated boron steel is first investigated through en- vironment scanning electron microscopy （ESEM） equipped with energy dispersive x-ray analysis （EDAX）. The cracking be- havior of the coating was evaluated using Gleeble 3500, a thermo-mechanical simulator under uniaxial plastic deformation at elevated temperatures. The extent and number of cracks developed in the coating were carefully assessed through an optical microscope. The coating layer under hot-dipped condition consists of an Al-Si eutectic matrix, Fe2Al7Si, Fe3Al2Si3 and Fe2Al5, from the coating surface to the steel substrate. The coating layer remains dense, continuous and smooth. During austenitization, the Al-rich Fe-Al intermetallics in the coating transform to more Fe-rich intermetallics, promoted by the Fe diffusion process. The coating finally shows the coexistence of two types of Fe-Al intermetallics, namely, FeAl2 and FeAl. Microcracks and Kirkendall voids occur in the coating layer and diffusion zone, respectively. The coating is heavily cracked and broken into segments during the hot tensile tests. Bare steel exposed between the separate segments of the coating is oxidized and covered with a thin FeOx layer. The appearance of the oxide decreases the adhesion of the Al-Si coating. It is found that the ductile FeAl is preferred as a coating microstructure instead of the brittle FeAl2. Therefore, the ductility of the Al-Si coating on hot stamping boron steer could be enhanced by controlling the ductile Fe-rich intermetallic phase transformations within it during austenitization. Experiments indicate that a higher austenitizing temperature or longer dwell time facilitate the Fe-rich inter- metallics transformation, increasing the volume fraction of FeAl. This phase transformation also contributes to reducing the crack density and depth.