Effect of deep cryogenic treatment on the microstructural,mechanical and ballistic properties of AA7075-T6 aluminum alloy

The study focused on investigating the effect of Deep Cryogenic Treatment(DCT)on the mechanical and ballistic properties of AA7075-T6 aluminum alloy.The microstructure,microhardness,tensile strength,and impact strength of the Base Material(BM)and DCT-treated 7075 samples were analyzed through metallographic analysis and mechanical tests.The microstructure of the DCT-treated 7075 samples revealed fine grains and a distribution of secondary phase particles.The tensile strength,impact strength,and microhardness of DCT-treated samples increased by 7.41%,4%,and 9.68%,respectively,compared to the BM samples.The fractography analysis of the tensile samples showed cleavage facets,microvoids,and dimples in both the samples.The ballistic behavior of the BM and DCT target plates were studied by impacting hard steel core projectiles at a velocity of 750±10 m/s.The target plates failed due to petaling and ductile hole enlargement,and the depth of penetration(DOP)of the DCT target was less than that of the BM target,indicating a higher ballistic resistance.The post-ballistic microstructure examination of the target plates showed the formation of an Adiabatic Shear Band(ASB)without any cracks.It was concluded that the DCT treatment improved the mechanical and ballistic properties of the aluminum alloy due to grain refinement and high dislocation density.

热处理条件对搅拌摩擦镁合金接头各区域抗弹行为的影响

采用搅拌摩擦焊(FSW)工艺制备AZ31B镁合金焊接接头,并在不同条件下进行热处理。研究AZ31B镁合金焊后热处理(PWHT)不同区域的抗弹行为,使用7.62 mm×39 mm穿甲弹,冲击速度为(430±20)m/s。分析热处理前后搅拌摩擦焊接头的显微硬度。结果表明,PWHT工艺(250°C,1 h)能提高热处理后搅拌摩擦焊接头的显微硬度。扫描电镜(SEM)结果显示,热处理使α-Mg晶粒细化,形成细小的析出相,使β-Mg17Al12相溶解到Mg基体中。通过穿深(DOP)试验评估PWHT不同区域的抗弹行为。热处理后接头母材区(BMZ)的DOP值较小。抗弹试验后对弹坑周边3个区域的横截面进行SEM表征,观察到绝热剪切带(ASB)的形成。