Nondestructive evaluation of mechanical properties of nanostructured Al-Cu alloy at room and elevated temperatures

The influence of processing variables on the mechanical properties of a nanostructured Al-10 wt.%Cu alloy was investigated.Stress-strain microprobe®system(SSM)and its automated ball indentation®(ABI®)test were used for evaluating the mechanical properties of this alloy.The tests were conducted at 21℃ on the bulk samples that were mechanically alloyed for 6 h at two ball-to-powder mass ratios(BPR)of 30:1 and 90:1.Furthermore,the tests were conducted at 200 and 400℃ on the samples that were processed at BPR of 90:1.Increasing BPR resulted in raising the final indentation load from(316±26)to(631±9)N and reducing the final indentation depth from 111 to 103μm.Regarding the samples that were processed at BPR of 90:1,increasing the test temperature from 21 to 400℃ resulted in decreasing the final load from(631±9)to(125±1)N and increasing the final depth from 103 to(116±1)μm.The sample processed at BPR of 90:1 and tested at 21℃ revealed the highest strength and the least deformability while the sample processed at BPR of 90:1 and tested at 400℃ exhibited the lowest strength and the greatest deformability,as compared to all samples under study.

Thermal stability of nanocrystalline Al-10Fe-5Cr bulk alloy

Thermal stability of nanocrystalline Al-10wt.%Fe-5wt.%Cr bulk alloy was investigated.The initial micro-grained mixture of powders was processed for 100 h using mechanical alloying(MA)to produce nano-grained alloy.The processed powders were sintered using high frequency induction heat sintering(HFIHS).The microstructures of the processed alloy in the form of powders and bulk samples were investigated using XRD,FESEM and HRTEM.Microhardness and compression tests were conducted on the bulk samples for evaluating their mechanical properties.To evaluate the thermal stability of the bulk samples,they were experimented at 573,623,673 and 723 K under compression load at strain rates of 1×10^-1 and 1×10^-2 s^-1.The annealed samples exhibited a significant increase in their microhardness value of 2.65 GPa when being annealed at 723 K,as compared to 2.25 GPa of the as-sintered alloy.The bulk alloy revealed compressive strengths of 520 MPa and 450 MPa at 300 K and 723 K,respectively,when applying a strain rate of 1×10^-1 s^-1.The microstructural stability of the bulk alloy was ascribed to the formation of iron and chromium containing phases with Al such as Al6Fe,Al13Fe4 and Al13Cr2,in addition to the supersaturated solid solution(SSSS)of Cr and Fe in Al matrix.