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。

Effect of heat treatment conditions on ballistic behaviour of various zones of friction stir welded magnesium alloy joints

Ballistic behaviour of different zones of post-weld heat-treated (PWHT) magnesium alloy (AZ31B) target against 7.62 mm × 39 mm armour-piercing (AP) projectile with a striking velocity of (430±20) m/s was determined. Magnesium alloy (AZ31B) welded joints were prepared by using friction stir welding (FSW) process and subjected to different heat treatment conditions. The microhardness values of non-heat-treated and heat-treated FSW joints were investigated. The results indicated that PWHT process (250 °C, 1 h) has improved the microhardness of heat-treated FSW joints. Scanning electron microscope (SEM) microstructure showed that heat treatment has caused the formation of fine α-Mg grains and tiny precipitates and made the dissolution of β-Mg₁₇Al₁₂ phase into the Mg matrix. The ballistic behaviour of PWHT zones was estimated by measuring the depth of penetration (DOP) of the projectile. Lower DOP value was observed for the base metal zone (BMZ) of a heat-treated welded joint. Post ballistic SEM examinations on the cross-section of all three zones of crater region showed the formation of adiabatic shear band (ASB).