352 Qin Shen et al.


Table 2. The Yield Strength (YS), Ultimate Tensile Strength (UTS), and Elongation-to-Failure (EL) for the As-Quenched (AQ) and 4-h-Aged Alloys.


Model Alloys Fe–NiAl, AQ


Fe–NiAl, 4 h


YS (MPa) UTS (MPa) EL (%) 306±3.5


380±1.0 Fe–NiAl–Cu, AQ 655±39.0


418±1.7 461±5.0 749±37.9


Fe–NiAl–Cu, 4 h 1,023±13.2 1,053±1.0


20.9±0.9 11.0±1.1 10.9±0.9 10.1±1.4


elongation-to-failure are summarized in Table 2. The Fe–NiAl alloy shows a yield strength of 306MPa and an ultimate tensile strength of 418MPa in the AQ condition. After aging for 4 h, the yield strength and the ultimate tensile strength increase to 380 and 461 MPa, respectively, together with a loss of elongation-to-failure from 20.9 to 11.0%. The addition of 1.63wt% Cu results in a substantial increase of ~300MPa in both the yield strength and ultimate tensile strength of the Fe–NiAl–Cu alloy in the AQ condition, with a loss of elongation-to-failure from 20.9 to 10.9%. In the 4-h-aged condition, significant aging strengthening is observed in the Fe–NiAl–Cu alloy. The yield strength and ultimate tensile strength dramatically increase to 1,023 and 1,053MPa, respectively, whereas the ductility remains nearly unchanged, exhibiting an elongation-to-failure of 10.1%. The dramatic increment of yield strength and ultimate tensile strength of the Fe–NiAl–Cu alloy demonstrates that Cu sig- nificantly enhances the age-hardening ability, in agreement with the hardness measurement results. In addition, without obvious sacrifice of ductility, the Fe–NiAl–Cu alloy shows a good combination of high strength and good ductility.


The fracture surfaces of the tensile samples are shown in Figure 3. For the Fe–NiAl alloy, there is no significant change


in fracture mode between the AQ and aged states, both show fine dimples (Figs. 3a, 3b), indicating a characteristic mode of a ductile fracture. TheAQsample of the Fe–NiAl alloy has more dimples than the aged sample, meaning that the AQ sample exhibits better ductility. The AQ Fe–NiAl–Cu alloy also shows a characteristic mode of a ductile fracture (Fig. 3c). After aging for 4 h, the sample of the Fe–NiAl–Cu alloy shows a mixed fracture mode, consisting of dimpled rupture and intergranular fracture (Fig. 3d).


The Evolution of Precipitates in the Fe–NiAl and Fe–NiAl–Cu Alloys To comprehensively understand the effect of Cu on the microstructural evolution of Fe–NiAl alloy, the APT inves- tigation was performed on the Fe–NiAl and Fe–NiAl–Cu alloys. Figure 4 shows Ni, Al, and Cu atom maps of the Fe–NiAl and Fe–NiAl–Cu alloys aged at 500°C for 0.5, 4, 32, and 128 h. No clusters or precipitates were detected in the Fe–NiAl sample aged for 0.5 h, and the distribution of Ni and Al appears uniform. The nearest-neighbor distribution (NND) analysis of this sample is shown in Figures 5a and 5b. It shows that there is no significant deviation between experimental data and random data curves, further suggesting that the Ni and Al atoms are mostly randomly distributed. On the other hand, a considerable number density of Ni, Al, and Cu clusters were observed in the Fe–NiAl–Cu alloy aged for 0.5 h, as shown in Figure 4b, which led to the development of weak nonrandom dis- tributions of the Ni and Al atoms revealed by NND analysis


Figure 3. Scanning electron micrographs of room temperature fracture surfaces for (a)Fe–NiAl, as-quenched; (b)Fe–NiAl, aged for 4 h; (c)Fe–NiAl–Cu, as-quenched; and (d)Fe–NiAl–Cu, aged for 4 h. Scale bar is 30 μm.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172  |  Page 173  |  Page 174  |  Page 175  |  Page 176  |  Page 177  |  Page 178  |  Page 179  |  Page 180  |  Page 181  |  Page 182  |  Page 183  |  Page 184  |  Page 185  |  Page 186  |  Page 187  |  Page 188  |  Page 189  |  Page 190  |  Page 191  |  Page 192  |  Page 193  |  Page 194  |  Page 195  |  Page 196  |  Page 197  |  Page 198  |  Page 199  |  Page 200  |  Page 201  |  Page 202  |  Page 203  |  Page 204  |  Page 205  |  Page 206  |  Page 207  |  Page 208  |  Page 209  |  Page 210  |  Page 211  |  Page 212  |  Page 213  |  Page 214  |  Page 215  |  Page 216  |  Page 217  |  Page 218  |  Page 219  |  Page 220  |  Page 221  |  Page 222  |  Page 223  |  Page 224  |  Page 225  |  Page 226  |  Page 227  |  Page 228  |  Page 229  |  Page 230  |  Page 231  |  Page 232  |  Page 233  |  Page 234  |  Page 235  |  Page 236  |  Page 237  |  Page 238  |  Page 239  |  Page 240  |  Page 241  |  Page 242  |  Page 243  |  Page 244  |  Page 245  |  Page 246  |  Page 247  |  Page 248  |  Page 249  |  Page 250  |  Page 251  |  Page 252  |  Page 253  |  Page 254  |  Page 255  |  Page 256  |  Page 257  |  Page 258  |  Page 259  |  Page 260  |  Page 261  |  Page 262  |  Page 263  |  Page 264  |  Page 265  |  Page 266  |  Page 267  |  Page 268  |  Page 269  |  Page 270  |  Page 271  |  Page 272  |  Page 273  |  Page 274  |  Page 275  |  Page 276  |  Page 277  |  Page 278  |  Page 279  |  Page 280  |  Page 281  |  Page 282  |  Page 283  |  Page 284