Surface integrity, recast layer formation and multi-objective optimization of AA4032-TiC-h-BN hybrid composites processed by WEDM

Aluminium-based hybrid composites that are machined utilizing the wire electrical discharge machining (WEDM) has attracted much attention due to the increasing demand for accurate machining the materials that are utilized in automobile and aerospace applications. The present work aimed to develop AA4032 alloy reinforced with TiC and h-BN particles to analyse the influence of reinforcement composition and WEDM parameters on machining performance and surface integrity. Five material compositions were produced and machined under different peak current (9-15A), gap voltage (30-40 V), and pulse-on time (50-100 µs). The results show that the enhance in pulse on time and peak current significantly increased the kerf width (KW) and surface roughness (SR) owed to the increase in spark energy and thermal erosion. The KW of the AA4032–6%TiC–2%h-BN composite was relatively lower in the range of 0.280 mm to 0.349 mm, while the kerf width of the AA4032 increased from 0.305 mm to 0.380 mm with an increased peak current. The surface roughness of AA4032 increased from 4.22 μm to 5.35 μm. Under higher machining settings, the highest roughness of about 5.82 μm was observed in the AA4032–6%TiC composite. The SEM examination revealed the presence of craters, microvoids, globules and microcracks, which became more severe with higher discharge energy conditions. The studies on recast layer specified that the addition of h-BN enhanced the thermal control and reduced the thermal damage, but the recast layers became larger and irregular with the increase of discharge energy. The hard TiC reinforcements resulted in the AA4032–6%TiC composite attaining a maximum hardness of more than 152 HV from cross-sectional microhardness testing. The hybrid composites containing h-BN exhibited improved surface integrity, recast layer thickness and dimensional accuracy, thus indicating their potential for precision WEDM applications.