**3.2 Mechanical properties**

The mechanical properties of ADI welded joints depends on the amount of retained austenite and its carbon content presence in microstructure [1, 2, 40]. Mechanical properties were varied with varying the austempering temperature and it's holding time due to the variation of microstructural constitutes, shape and size, nodularity and numbers of nodule presence in per mm2 . At 300°C austempering temperature microstructure consists of needle shaped bainitic ferrite with small amount of retained austenite indicates higher tensile strength and hardness with lower the toughness. However, at 350°C austempering temperature structure shows feathery shaped bainitic ferrite with higher amount of retained austenite indicated lower tensile strength and hardness with higher toughness and fatigue strength. The average mechanical properties of both the weld metals (Trial 4 and Trial 7) after austempering at 300 and 350°C for 2 h holding time are given in **Table 4**.
