Thermostablity Study on Microstructure and Microhardness of Laser Shock Processed Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si

Abstract

In this paper, the microstructure and microhardness of laser shock processed (LSP) Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si titanium alloy with and without annealing were examined and compared. The titanium alloy samples were LSP processed with 3 layers at 4.24GW/cm2. Some of the samples were vacuum annealed at 623K for 10 hours. The microscopic structure with and without annealing were tested and analyzed by SEM, TEM. The results indicated that after LSP, the shock wave provided high strain rate deformation and led to the formation of ultra-fine grain. Comparing with the samples without annealing, the dislocation density was lower and the grain-boundary was more distinct in the annealed samples, but the sizes of the ultra-fine grain didn’t grow bigger after annealing. On the other hand, the microhardness measurement was made on the cross-section. It is obviously that the laser shock processing improved the microhardness of the Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si for about 12.2% at the surface, and the hardness affected depth is about 500 microns. The microhardness after annealing is 10 HV0.5lower, but the affected depth is not changed. The titanium alloy after LSP is thermostable at 623K; thus break the USA standard AMS2546, in which titanium parts after LSP are subjected in subsequent processing should not exceed 589K.

Effect of Residual Stress and Microstructures on 316 Stainless Steel Treated by LSP

“…Therefore, Laser shock processing (LSP) is a surface treatment technology. It has morphed into a favored surface treatment technology due to its special advantages of non-contact, excellent controllability and no heat-affected zone [3][4][5]. This technique applies shock waves to materials surface and treats the target through localized plastic deformation.…”