T i6Al4V alloy has the properties of small density, high strength and good corrosion resistance. However, Ti6Al4V alloy castings are prone to shrinkage porosity due to its poor fluidity, leading to the poor performance of components. The defects must be reduced to a minimum level, especially in the field of aerospace and other high-quality-requirement industry. Hot isostatic pressing (HIP) has been proved to be a very effective way to eliminate or reduce shrinkage. A workpiece is heated and put under uniform pressure by inert gas, and the shrinkage is eliminated without changing the shape by the mechanism of plastic deformation, creep and diffusion bonding [1][2] . For decades, remarkable work has been done on the effect of HIP temperature on alloy's densification and microstructure. Gang Wang [2] et al. have studied the influence of HIP temperature on the microstructure of 2A12 powder compact. It was found that the microstructure
Abstract:The Ti6Al4V alloy castings were produced by the investment casting process, and the hot isostatic pressing (HIP) was used to remove shrinkage from castings. The processing pressure and holding time for HIP were 150 MPa and 20 min, respectively. Four different HIP temperatures were tested, including 750 ºC, 850 ºC, 920 ºC and 950 ºC. To evaluate the effects of temperature on densification and microstructure of Ti6Al4V alloy treated by HIP, non-destructive testing and metallographic observation was performed. The experimental results show that the shrinkage was completely closed at 920 ºC and 950 ºC. The densification of Ti6Al4V alloy increased as the HIP temperature increased below 920 ºC. The lamellae were more uniform, the thickness of lamellae was obviously broadened and the structure was coarsen. Besides, the Norton creep equation was used to simulate the effect of different temperatures on the densification of Ti6Al4V alloy during HIP. The simulation results were in good agreement with the experimental results. It was also found that 920 ºC is a suitable temperature for HIP for Ti6Al4V alloy.Key words: Ti6Al4V alloy; hot isostatic pressing; temperature; casting shrinkage; densification; microstructure of raw powders changed from a dendrite structure to an equiaxed structure from room temperature to 600 ºC. Lei Xu [3] also investigated the effects of temperature and pressure on microstructure of powder compacts during HIP. Through the comparison of the samples HIPped at 800 ºC and 910 ºC, it was found that more stable and homogeneous microstructure can be obtained at higher temperature. Chung-Hung Tam [4] et al. have studied the effects of three different HIP temperatures 1,323 K, 1,373 K and 1,423 K on the densification of Cr-Si targets, and it was found 1,373 K was a suitable HIP temperature for the three Cr-Si targets. Yu Zhou [5] investigated the effects of HIP temperature on the densification of Nibased superalloy. It was found that HIP temperature played a dominant role in the cavity healing process. With gradually increasing HIP temperature, the cavity healing behavi...